Texas Instruments TI-99/4A

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The Texas Instruments TI-99/4A is a home computer, released June 1981 in the United States for $ 525 ($ 1,400 adjusted for inflation). This is an enhanced version of the less successful b TI-99/4 model, released in late 1979 for $ 1,150 ($ 3,900 adjusted for inflation). Both models include support for sprites and multi-channel sound, some of the first home computers to include custom hardware, along with the 8-bit Atari family were also introduced in 1979.

Video Texas Instruments TI-99/4A

Features

TI-99/4 has a chiclet-style keyboard calculator and a character set that does not have lowercase text. TI-99/4A adds additional graphics modes, "lowercase" characters consisting of small capital letters, and full travel keyboards. Both use a 16-bit processor, making TI-99/4 series the first 16-bit home computer.

TI-99/4A CPU, motherboard, and ROM cartridge ("Solid State Software") slot built into the keyboard. The power regulator is placed below and in front of the cartridge slot below the slant area to the right of the keyboard. This area gets very hot so users usually refer to it as a "coffee cup warmer". An external power supply, different according to the sales country, is a step-down transformer.

Available peripherals include 5 "floppy disk drives and controllers, RS-232 cards consisting of two serial ports and one parallel port, P-code cards for Pascal support, thermal printers, acoustic couplers, tape drives using standard audio cassettes as media , and a 32 KB memory expansion card TI-99/4 sold on computers and monitors (13 modified Zenith colored TVs) because Texas Instruments was unable to obtain a RF modulator approved by Federal Communications of the US The timely commission TI-99/4A sending with RF modulator.

In the early 1980s, IT was known as a pioneer in speech synthesis, and the highly popular plug-in speech synthesizer module is available for TI-99/4 and 4A. Speech synthesizers are offered free with the purchase of a number of cartridges and are used by many video games written by TI (prominent titles offered with speeches during this promotion are Alpiner and Parsec ). Synthesizer uses a linear prediction encoding variant and has a small vocabulary built in it. The initial goal is to release a small cartridge that is attached directly to the synthesizer unit, which will enhance the device built into the vocabulary. However, the success of the text-to-speech software in the Terminal Emulator II cartridge canceled the plan. In many games (mostly produced by TI), speech synthesizers have a relatively realistic sound. For example, Alpiner ' s includes both male and female voices and can be very sarcastic when players perform bad steps.

The original TI-99/4 expansion concept was that the device would be connected serially to the console and to each other, in "daisy chain" mode. The "sidecar" extension unit can be connected together in a sustainable chain, but can quickly occupy the entire desktop and cause crashes and locks due to the number of connectors on the system bus.

This original idea was soon replaced by a system based on expansion cards. Wrapped in silver plastic but made of sheet steel, this plug into a large "Peripheral Expansion System" (usually known among IT owners as Peripheral Expansion Boxes or "PEB"), eight slot chassis, containing its own linear power supply and full- height 5Ã,¼ "floppy bay.Each card also has its own" access light ", an LED that will blink or blink when the card is being used by the software.As with the previous S-100 bus, part of the power supply that the card slot strength is not arranged Each card has an on-board regulator for its own needs, thereby reducing power consumption on partially PEB and allowing for future expansion cards that may have unusual voltage requirements.

PEB also carries analog voice inputs on the expansion bus. This allows IT audio Speech Synthesizer to be brought through the console to the monitor. Audio is also carried over the ribbon cable ("firehose", as IT users often call it) to the Peripheral Expansion System, both allowing the relocation of Speech Synthesizer into the Expansion box and allowing possible audio cards that offer more features. from the built-in voice of the console. No "official" card from Texas Instruments has ever used this path.

The initial model (TI-99/4, identified by its keyboard and " (C) 1979 TEXAS INSTRUMENTS " on the title page) includes the built-in equation calculator, but in 99/4A (" C) 1981 TEXAS INSTRUMENTS ") this feature is discontinued. All consoles include TI BASIC, a BASIC programming language translator that complies with ANSI-compliant which is largely incompatible with Microsoft's more popular, and often replicable BASIC. Then the console, identified by " (C) 1983 TEXAS INSTRUMENTS V2.2 " on the title page, also removes the system's ability to run unlicensed ROM-based cartridges, locking third-party manufacturers such as Atarisoft.

The system has a joystick port that supports two digital joysticks, called TI as "wired remote control". The two joysticks are connected through a pin of a pin nine pin DE-9 port that is identical to that used for the Atari 2600 joystick but with an incompatible pin. An aftermarket adapter is available that allows the use of two compatible Atari joysticks. The computer supports storage to, and loads of, two cassette drives through a dedicated port. Composite video and audio are ejected through other ports on NTSC-based machines, and incorporated through an external RF modulator for use with television. PAL-based machines produce more complex YUV signals that are also modulated to UHF externally.

The first personal computer with a 16-bit processor

The TI-99/4 series holds the distinction as the first 16-bit personal computer. TI-99/4A has a 16-bit TMS9900 CPU running at 3.0 MHz. TMS9900 is based on the TI IT-990 range of mini computers.

Only Register Program Counter, Status Register, and Workspace Pointers are in the chip; all work registers are stored in RAM at the address indicated by Workspace Pointer. 16 registers are available at certain times, and context-shifting instructions that are changed to another workspace automatically allow for fast context switches compared to other processors that may have to store and restore registers. For CPU RAM, the machine has only 256 bytes of "scratch" memory to support workstation storage. This memory is placed directly on a 16-bit bus with zero waiting state, making it much faster than other available memory for the system.

Although the CPU is a full 16-bit processor, only the system ROM and 256 bytes of scratchpad RAM are available on a 16-bit bus. All other memory and peripherals are connected to the CPU via a 16-to-8-bit multiplexer, requiring two cycles per access and introducing an additional 4-cycle wait state. (This is reportedly due to the failure of the new 8-bit processor designed by TI for this system, while the 9900 processor is already in production and proven.) The popular user modification in subsequent years involves static RAM chips "stacked" onto a 16- bit console, allowing the expansion of 32kB of standard RAM without waiting and approximately 30% increase in speed for many applications. Applications that previously run entirely in 8-bit RAM (both code and register) can be accelerated by a factor of two. Most hardware is based on the system clock, not the speed of program execution, and hardware access still runs through an 8-bit bus with an intact waiting state, so this particular modification does not affect any devices.

By decoding some unused I/O-bits in the console, it is also possible to use the full address range of 64 kB of RAM in the machine, by overlaying the memory and/or other ports, under I/O (CRU) control. Thus the ROM console can be copied to RAM, and thus things like interrupt vectors and such can be modified. However, such modifications are not frequent enough to get anyone but certain modifiers themselves who write whatever software to use them.

The video display processor at 99/4 is TMS9918. It has no bitmap mode, which is added in 99/4A. VDP on American 99/4A is TMS9918A (which gives machine A in its name). In this European PAL console is replaced with TMS9929A ​​â € <â €

The unique feature of this VDP chip is that they contain hardware support to superimpose the graphics on the screen above other video signals. Although TI announced a peripheral card called the Video Controller Card that allows the choice of laser control players, which can switch between the IT display and the laser player, the 9918 genlock capability is disabled in the 99/4A design and requires hardware modifications to be used.

All access to the VDP system is executed 8 bits at a time. Although this affects performance, it makes it easier to upgrade VDP when newer, relatively compatible chips are released by Yamaha. Peripherals from Mechatronics, and Michael Becker, simply called "80-column cards" include the VDP Yamaha V9938 which delivers 99/4A resolutions over 512ÃÆ'â € "424 in 16 colors or 256ÃÆ'â €" 424 in 256 colors. It also increases VDP memory from 16K to a maximum of 192K, although only software is written explicitly for 9938 that utilizes it.

The unusual architecture of the 99/4 series is documented to be due to a 9985 failure, an 8-bit processor being made specifically for the machine. When left out, 16-bit 9900 is chosen to replace it, and many "glue logic" should be added to fit the processor into the existing design, while no changes are made to take advantage of the 9900's power.

"Install and play" hardware support

All TI-99 models, from the earliest TI-99/4 to TI-99/2 and TI-99/8, including plug and play support for all peripherals. Device drivers (called "Device Service Routines", or DSRs) are built into ROM in hardware; when a new card is inserted, the card is immediately available for any software required or wants to use it. All device access uses a generic file-based I/O mechanism, enabling new devices to be added without updating the software to use them. The Communication Signup Unit (CRU) can handle 4096 devices; However, every IT card runs on the cable address on the CRU bus, so some cards of the same type can not be supported without modification. The only official card known to be modified is the RS-232 card, which supports two different base addresses. This allows the system to support four RS-232 ports and two parallel printer ports. Four-line BBS is running, using the correct jumper series card, on a recent TI-99/4A system in the mid-1990s.

Most cards created by fans released after IT's release of the personal computer business include switches to set basic CRU addresses.

The HexBus interface was designed in 1982 and intended for commercial release in late 1983. It connects consoles to peripherals via high-speed serial links. Despite the current prototype for USB (plug and play, hot-swappable, etc.), it was never released, with only a small number of prototypes appearing in the hands of collectors after IT was pulled out of the market. Some HexBus peripherals have been planned or produced. The WaferTape hard disk never made it past the prototype stage because of reliability issues with tapes. The 5.25-inch floppy drive also never made it past the prototype stage, even though it did work. The DSDD disk controller prototype and the Video controller are also created. Four-color printers, 300-baud modems, RS-232 interfaces, thermal/80-column inks, and 2.8 "Fast Disk" drives are the only devices released in large numbers, mostly for use with Compact Computer 40 (CC-40). All HexBus devices can be used with TI-99/4A when connected via HexBus Interface, via direct connection to TI-99/8, or via direct connection to CC-40.

RAM CPU and Scratchpad

Computer-inspired IT architecture of the TMS9900 series means that the "Workspace" registers currently in use are stored in main memory. Because static RAM was also very expensive in the early 80s, TI only gave a fast 256 byte RAM "start pad" machine where registers of workspace could be stored.

The original design for the intended CPU has 256 bytes internally for the CPU itself, but the 9900 requires registers to be on external memory. Placing a small amount of this memory on a 16-bit bus still helps engine performance (compared to having registers in 8-bit RAM with 4-cycle penalty for each access). Some programs, such as Parsec , copy a short loop of code into this memory to utilize performance.

The box and PE expansion box system allows the official 32KB RAM expansion. This is not available for all uses - for example the Extended Basic program is limited to using 24kB with the remaining 8kB available for machine code routines.

The third party provides a replacement memory card for PEB. For example, Myarc produces 192kB and 512kB cards. The memory provided by the Myarc card can be partitioned for use as ordinary CPU RAM, RAM disk and printer buffer.

The Memory Mini plug-in modules also contain 4kB of RAM that can be used as persistent RAM disks (containing button cells) or to load machine code programs.

It is also possible to add 8kB "supercart" or 32kB "superspace" cartridges through the cartridge slot, which also includes the GROM Editor/Assembler. It uses the cartridge ROM space.

RAM and GPL VDP

Texas Instruments engineer delivers a 16KB RAM Video Display Processor (VDP) to TI99/4A graphic copiers, TMS9918A. VDP RAM is DRAM, with VDP handling refresh. It can be expanded up to 192kB with the use of Yamaha V9938 as a user-designed modification (not a standard upgrade option).

VDP RAM is also used to store buffers for disk I/O, and variables and code for the user BASIC program. Therefore, the largest BASIC program may be less than 16kB. BASIC is implemented in the TI-99 series using a second translated language called Graphics Programming Language (GPL). The GPL Interpreter lives in the ROM and controls the machine while power-up, and is very close to the original 9900 machine code, adding instructions to transparently access different types of memory in the machine and perform higher level functions such as copy and formatted memory. Users who install memory expansion still need to upgrade to an Extended BASED cartridge to use it instead of VDP RAM.

The same VDP is used in MSX and ColecoVision machines. Further increases in chips, 9938 and 9958, are manufactured by Yamaha based on IT design. Boards are created that take advantage of these new chips to enhance the graphics capabilities of TI-99/4A. The 9938, which is more common than the two upgrades, allows 512 ÃÆ'â € "424 pixels with 16 colors, or 256 ÃÆ'â €" 424 on 256 colors. This upgrade is not a simple drop-in and replacement; Small boards including VDP replacement and VDP RAM replacement (usually 128kB) are required. In addition, although most chips are compatible software, certain bugs in ROM cause compatibility issues with new chips. One board, 80-column Mechatronic card featuring 9938 requires the user to press a button when entering TI BASIC.

Graphics Read-Only Memory

Read-Only Memory Graphics is a set of memory that is accessed one byte at a time through a dedicated memory port, and is a fully automated read-only device. (There is also support in the console for 'GRAM', a simulator made by third parties later.) Most of the IT cartridges (Disk Manager 2, Editor/Assembler, TI Writer, most games) use this system, such as whether the IT-BASIC console. Swapping GROM IT-BASIC with GROM removed from favorite cartridges is a popular modification, as installing multiple GROMs into one cartridge enables "multicart", with all GROM included available in the boot menu.

Because standard machines do not allow third-party machine language support, programmers find that their market is clearly limited to users who actually add more RAM to their systems. This limitation was reduced because the price of 32 kB expansion cards and 4 kB "Memory" module finally fell, but by that time the market had moved to another computer.

Some advanced cartridges (eg Parsec , Alpiner , TI LOGO, TI Extended BASIC) include addressable ROMs available for machine code, especially for games or applications requiring code speed machine. None of this memory is available to users. In general, cartridges equipped with ROM can be identified by having a 28-pin IC on the board, while the GROM IC has 14 pins. A small amount of cartridge also includes a small amount of RAM (especially games produced for Milton Bradley's MBX expansion system).

Tigervision developed a unique solution for standard memory card slot restrictions; a 24kB cartridge attached to the side expansion interface, mimicking the expansion device. This allows the company to implement a larger game entirely within the machine code. The Tigervision cartridges use expansion ports including Espial and Miner 2049er . The third cartridge, Sprinter , was listed in the 1984 catalog but was not released. Exceltec also released two similar side cartridges, Arcturus and Caterpillar Killer .

Due to speed congestion (multiplexer 16-to-8-bit buses) and BASIC interpreted multiple folds, the TI-99 series gained a reputation as something unique and eccentric, which made it popular and angered others. Many people who just experience IT BASIC also consider it very slow, although the assembly program actually manages a pretty good speed although hardware problems can be overcome.

Maps Texas Instruments TI-99/4A

Games

Developers created about 100 99/4A games, mostly published by Texas Instruments. Some of the most popular are Parsec, Apple Invaders, Munch Man, Alpiner, Tombstone City: Century the 21st , Hunt The Wumpus and Wars Car .

Many video games developed by IT, especially those developed by John Phillips, may be forced into "cheat mode" by holding down the shift key and pressing 838. Messages often appear, allowing users to move to different game rounds.. At the Munch Man , top screens and top spins include an invisible Hooos ("ghost" in Pac-Man descendants) that travel several times faster than Munch Man. In Alpiner , players can choose which mount to climb. 838 (with or without SHIFT) on Star Trek provides torpedo, shield, and random but high-energy warp-drive levels.

InfoWorld is criticizing the computer game library as mediocre. TI does not support third-party development for 99/4A, including games, but does not license popular arcade games like Zaxxon or Frogger . The company actively promotes TI-99/4A in educational use (compared to Atari and Commodore emphasis on arcade-game action) and a children's learning program comprising most of its software libraries. But because Apple II has had a major foothold in schools, in the US, and is an open architecture that anyone can easily develop, TI fails to make an impact there.

src: www.classiccmp.org

History

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In 1977 a group within Texas Instruments was designing a video game console, a home computer to compete with TRS-80 and Apple II, and a high-end personal computer business with hard drives. The first two groups joined the IT consumer product division in Lubbock, Texas; 99/4's (according to Walden C. Rhines) "ultracheap keyboard", RF modulator, and ROM cartridges come from the console design. Others inside the company persuaded the Lubbock group to use TI TMS9900 CPU.

99/4

Although IT was much bigger than any other personal computer company when it entered the market in 1979, $ 1,150 TI-99/4 was, The New York Times <1989> stating, "an embarrassing failure". David H. Ahl states that it's "very expensive, especially given the odd keyboard, non-standard Basic, and lack of software". Adam Osborne reported in July 1980 that despite poor sales, IT had raised the price of the complete system to $ 1,400, making computers more expensive than the more popular Apple II, available for only $ 950. "Some dealers, who have offered the system complete (including monitors) at a price less than Apple, still can not sell it, "he added.

Two years after the 99/4 debut, TI released 99/4A, very similar but with a better keyboard and more expansion options. By lowering the price and offering a discount, TI sells more computers; it has been estimated that it's about 35% of the home computer market at its peak.

In 1982, TI started a price war with Commodore International by lowering the 99/4A road price to $ 200, including a $ 100 rebate, to compete with a $ 300 Commodore VIC-20 for $ 300. IT spokesman Bill Cosby joked how easy it was to sell computers by paying people $ 100 to buy one, but the company continues to lose shelf space, as Commodore matches the $ 200 retail price in December 1982.

President Spectravideo later said that "IT has been sucked by" Jack Tramiel, head of the Commodore. TI was forced to sell 99/4A at the same price as the VIC-20, though it was much more expensive to produce. Although TI and Commodore each have their own IC fabrication facilities, Commodore creates custom ICs to reduce the cost of computers, while IT continues to use off-the-shelf components and only makes relatively small revisions to their motherboards. Commodore also makes other cost-cutting changes including using aluminized cartons to create RF shields for some of their systems. TMS9900 requires costly special semiconductor packaging; IT continues to use high quality components and materials with unfulfilled expectations that the market will recognize.

In mid-1982 Jerry Pournelle wrote that TI "practically delivers TI-99/4A". An industry joke states that the company loses money on every computer, but keeps it up in volume. The list price of 99/4A was $ 400 that fall, but the street price including a $ 100 rebate was around $ 200. Sales peaked at 30,000 a week in January 1983, but on January 10, 1983 the Commodore lowered its computer prices; the wholesale price of VIC-20 is $ 130. In February, IT responded by lowering the retail price of 99/4A to $ 150. In April the Commodore lowered the price again, and the retail price of the VIC-20 package reached $ 100. TI also lowered the price and offering discounts, reducing the retail price of 99/4A to under $ 100; at this time the company is likely to lose money on each computer. In early 1983 IT stopped sales for a month to fix defects, but - predicted in April that the home computer market that year would be much larger than most industry analysts expected - production continued at an annual rate of three million, increased inventory. In May began offering PEB for free with the purchase of three devices; at this time IT uses discounts as the main marketing 99/4A. In August the company reduced peripheral prices by 50% and offered $ 100 free software; in September, it reduced software prices by up to 43%.

Termination

The Times stated in June 1983 that the $ 100 Cosby refund "joke is no longer funny", and that "the future option is very thin" for TI; L.F. Rothschild estimates that the company will only sell two million computers. Cheap price may damage 99/4A reputation; "When they go to $ 99, people start asking 'What's wrong with that?'", Says a retail executive.

After losing $ 111 million after taxes in the third quarter of 1983, TI announced in October 1983 that it halted 99/4A, while continuing to sell a compatible MS-DOS Professional IT computer. (IT shares rose by 25% after the announcement, due to another firm's strong business.) With other IT discounts, the retailer sold the remaining inventory of $ 1,150 of Christmas computers for $ 49; The Child World 90 store soon sold more than 40,000 computers at a price, and riots almost broke out in Greensboro, North Carolina Kmart as buyers quarreled with computers. Discontinued during the 1983 video game crash, 99/4A became the first in a series of home computers to be orphaned by their manufacturer over the next few years, along with Coleco Adam, Mattel Aquarius, Timex Sinclair 1000 and IBM PCjr. A total of 2.8 million units were shipped before TI-99/4A was suspended in March 1984.

Lack of third-party development

TI-99/4A is more powerful than VIC-20, offering more memory and more advanced graphics capabilities. However, a number of design elements invite criticism. All peripherals connect directly to the right side of the unit (unless the user purchases expensive and heavy Peripheral Peripheral Boxes), which causes the computer not to fit properly on the table if the user adds many peripherals in addition to tape drives and printers. Additionally, the 48-key keyboard layout does not match a very tight typewriter, and there is (at the time) no option for an 80-column view. The limitations of the keyboard and display make it unpopular for word processing.

IT can not generate a profit on TI-99/4A for $ 99, but hopes selling a lot of cheap computers will boost sales of more profitable software and peripherals. Because such a razor-and-knife business model demands that the product be his own, IT continues to closely monitor machine progress, discouraging fans and third-party developers. A Spinnaker Software executive says that 99/4A has "the worst software in the business", and Ahl notes that unlike other computers, it does not have "Microsoft BASIC, VisiCalc , WordStar , or any popular games ". Citing Money's Money Kilniud Microcomputing publisher Wayne Green reported in August 1980 that IT plans only had 100 applications available by the end of 1981, stating that "This small figure should put cold across the industry ". The peripheral costs about twice as much for another computer. IT joysticks, for example, are of poor quality and hard to find; one retailer reported that his best-selling product was the Atari adapter cable.

Green said that although his company Instan Software has published "hundreds of programs for TRS-80 [and] want to translate as much as possible to use on TI-99/4", it can not find anyone among more than 1,000 developers. in his network that can send software to a computer, adding "We understand the problems with the system and the Texas Instruments effort made to make the translation difficult". Rival companies are much more open with information. The next issue of Kilotoud Microcomputing reported that the Commodore executives promised that the upcoming VIC-20 would have "enough additional documentation to allow an experienced programmer/hobbyist to go inside and let his imagination work." IBM released full software and hardware information for Personal Computers when it announced it in 1981, stating that "the definition of personal computers is third-party hardware and software".

Pournelle in 1982 writes that because "more than half the stuff that's great for microcomputers comes from fans and hackers... the wrong one has incorrectly concluded that they are... unimportant", it "finds itself alone, cut off from the mainstream ". He believes that IT recognizes his mistakes and will change. However, companies insist on selling other people's software, which is rejected by many developers. After third-party developer games for Atari 2600 became very successful, IT in June 1983 Consumer Electronics Show announced that only cartridges with IT licensed circuits would work on 99/4A. The Boston Phoenix predicts that "most [software developers] will not bother making versions compatible with IT from their programs". Pournelle wrote after the announcement that "TI once again told fans to drop the dead".

No official technical documentation from TI was released until the assembly language development suite "Editor/Assembler" was released in 1981, and no system scheme was ever released to the public until after IT stopped the computer. In addition, the awkward architecture of TI-99/4A and nonstandard CPUs (compared to 6502 and Z80 that all programmers were familiar with at the time) made it difficult to develop.

Cult follows

TI-99/4A retained the following sect for many years after its death in the market, partly because of its eccentricity, and partly because IT actively supports user group networks during machine production. It has finally come to achieve the following cult among retro-computer hobbyists. In 2004 Universal Serial Bus (USB) cards and Advanced Technology Attachment controllers for IDE hard disks for PEB are released, and there is still an annual IT IT TI where people gather to celebrate TI-99 historic computer families. Third party devices such as expanded memory cards, improved floppy controllers, and hardware ramdisks are a very stable and popular addition to the machine, although no current source is known for this device. In the early 1980s, the bulletin board system (TIBBS), developed by Ralph Fowler of Marietta, Georgia, running on 99/4A became very popular and brought many users together. Also, a number of emulators for TI-99 exist today for PC-based systems.

There are also siblings that are portable to TI-99/4A. Nicknamed CC40 (Compact Computer 40), it is a compact battery powered with LCD screen and BASIC IT version. It also pioneered the TI HexBUS interface, a high-speed serial expansion port similar in concept to USB. HexBUS devices are compatible with all family members of TI-99; The CC40 cartridge does not.

In 1987, "Turbo XT" was introduced by Triton. Although rare, it allows TI-99/4A and IBM PC XT to share the same desktop space, albeit without sharing things like memory or disk drives. Turbo XT has at least two serious failures - first, it extends the use of an IT keyboard that is already marginal to XT whereas otherwise it would be far more valuable; secondly, it does not allow IT to share or use resources with XT (special BIOS may have enabled XT to function as a ramdisk, diskette/drive controller and serial port).

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Successor and clone

By the time they leave the home computer market, IT has been actively developing two successors to TI-99/4A. Both enter production, although several prototypes are each in the hands of the TI-99/4A collector. Therefore, both machines will be much faster than the original TI-99/4A, and both use the TI "HexBUS" serial interface (which is available as an option on TI-99/4A and can be seen as a prototype for USB everywhere when this - a link for TI-99/8 includes some HexBUS peripheral images).

• TI-99/2, 4K RAM computer, 32K ROM without color port, sound, or Mylar joystick and keyboard. IT designs computers in four and a half months for sale under $ 100 and competes with Sinclair ZX81 and Timex Sinclair 1000. Based on the TMS9995 CPU running at 10.7 MHz and with built-in RF modulator, performance is greatly improved when the screen is blank. University of Southwestern Louisiana develops system software. The 99/2 software is run on 99/4A, but not vice versa. Working prototypes appeared in the January 1983 Consumer Electronic Show (CES). The price of home-computers declined so quickly, however, by mid 1983 the price of 99/4A sold for $ 99. The company canceled 99/2 in April 1983, but plans to show it off at CES June until another company's press conference there indicated that competition would increase.
• TI-99/8 and 99/6 99/8 reportedly have a wholesale price of $ 200. Personally addressed to the dealer but not announced at CES in June, and officially canceled in October 1983. With 64 kB of RAM can be enlarged up to 15 megabytes, larger keyboard, integrated sound synthesis, Pascal operational environment integrated with Pascal UCSD and 16 full -bit data buses available on the expansion port. Designed by Texas Instruments, but abandoned at the prototype stage. Some prototypes are known to exist. In addition, the MESS emulator can run what is believed to be a system ROM.
• Myarc Geneve 9640, an enhanced TI-99/4A clone built by Myarc as a card for entry into the IT Peripheral Expansion System and using a separate IBM PC/XT keyboard. Released in 1987, it was in many ways similar to the previous TI-99/8 prototype in early 1983. This included a faster processor (12 MHz TMS9995), improved graphics with 80-column text mode (via 9938), RAM 16-bit width, MDOS, and compatible with almost all software and hardware installed in the slot (adapter available to allow only Speech Synthecizer to be installed inside PEB). The toggle switch is fitted to the PEB side to allow insertion of wait state to bring the computer to the same speed as the original console, allowing compatibility for games and other important software.
• SGCPU, Second Generation CPU card released by 99 System User Groups in 1996 as a card to be installed on PEB. It's also known as TI99/4P, and includes standard 9900 CPU, ROM, and up to 1 MiB of 16-bit RAM using the 'AMS' memory expansion scheme. This card requires an HSGPL card, which provides the GROM emulation required to run the system, and EVPC, which includes a 9938 video processor for display.

• Tomy Tutor and his brother's system are Japanese computers that are very similar in architecture and firmware to 99/8. Unlike the 99/8, it was released commercially, but sold very poorly outside of Japan. Parts of the operating system and BASIC code are similar to 99/8. According to Barry Boone (renowned programmer for TI-99/4A), BASIC's built-in Tutor uses the same internal byte token as well as TI's Extended BASIC, and many memory scratchpad locations are placed on the same relative location as TI-99/4A and TI-99/8. For example, the keyscan value is returned at offset & gt; 75 and floating point stored in & gt; 4A.
• The Phoenix G2, designed in 2010 by Gary Smith, a member of the TI-User Group UK. This machine uses two FPGAs to mimic the entire Myarc Geneve 9640 architecture and TMS9995 microprocessor, thus eliminating the dependence on obsolete silicon devices. It combines the latest technological advances, such as SD card reader, ethernet, full VGA output, and now 64 MB RAM.

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Technical specifications

• CPU: TI TMS9900, 3.0 MHz, 16-bit, 64-pin DIP.
• Memory: RAM VDP 16Ã, kB (RAM Video Processor Display), plus 256 bytes of fast CPU "scratchpad RAM" intended for TMS9900 processor to maintain "workspace" registers.
• Video: TI TMS9918A VDP (TMS9918 at the beginning of 99/4, TMS9929/9929A ​​â €
• 32 single-color sprites in the specified layer allow higher-numbered sprites to transparently flow over the lower-numbered sprites. Sprite is available in 8 Ã- 8 pixels or 16ÃÆ'â € "16 pixels, with a little 'zoom' that doubles all sprite sizes but not the resolution. One bit is available on hardware for chance (collision detection), and the console supports automatic movement through the interrupt routine in ROM. There should be no more than 4 sprites visible per horizontal scanline.
• 16 fixed colors (15 visible, one color provided for 'transparent' showing background color). Transparent is intended for the functionality of genlock 9918 used in conjunction with the IT Video Controller Card. This feature was demonstrated in October 1999 at an international IT meeting near Stuttgart, Germany. (This requires hardware modification to the console itself, since the video input channel is not directed to the motherboard.)
• Text mode: 40ÃÆ' â € "24 characters (256 6ÃÆ' â €" 8 user-defined characters, no sprite, foreground and background color only, not accessible in BASIC)
• Graphical mode: 32ÃÆ'â € "24 characters (256 8ÃÆ'â €" 8 user-defined characters, 15 full transparent color palettes (available in group 8 via character table) and 32 sprites (The only mode available in BASIC Extended BASIC is required for sprites, and can only access 28 of them.)
• Bitmap mode: 256ÃÆ'â € "192 pixels (no more than two colors in eight pixel lines, 15 full transparent color palettes, all 32 sprites are available but motion-based interrupts through ROM routines not due to memory layout, not available for BASIC or the original 9918). Bitmap modes can be arranged in such a way as to use less memory but still provide enhanced color or enhanced layout patterns, leading to the popularity of so-called "bitmap half" modes. Actually this mode is not an undocumented mode of VDP (which completely docs this masking) but only the clever layout of Bitmap mode.
• Multicolor mode: 64ÃÆ' â € "48 pixels (each pixel can be any color, all 32 sprites are available)
• All of the above consists of 36 "layers" starting with video overlay input, then background color, then two layers of graphics mode, then layers for each of 32 sprites. The higher layer obscures the bottom layer of hardware, unless the higher layer is transparent.

Voice: TI TMS9919, then SN94624, identical to SN76489 used in many other systems.

• 3 votes, 1 vote (white or regular).
• The sound produces a square wave from 110 Hz to about 115Ã, kHz.
• Console ROM includes playback of interrupt driven music list.

src: i.ytimg.com

Contemporary usage

TI-99/4A enjoy life after being active in the world of vintage computing enthusiasts. There are currently three very active mailing lists where TI-99/4A owners correspond to each other, from matters relating to hardware and interface equipment to machine settings, to advanced software techniques.

• TI-99/4A Programming Forum (AtariAge) - an active forum, with hardware and software projects on TI-99/4A.
• TI-99/4A Online User Group (OLUG) - mailing list, with a general chat about all things IT.
• TI-99/4A and the Compatibles Discussion Group - a more technical-oriented mailing list, where people will often post technical questions or software routines to try.
• Mailing List of SWPB Programmers - SWPB list is a mailing list dedicated to discuss programming code/assembly machine language on CPU TMS9900 (SWPB is assembly instruction, which means "byte swap" in Assembly Language TMS9900).

src: www.oldcomputr.com

The development of modern hardware

There has been a resurgence in new hardware projects in recent years. Recently, various plug in cartridge boards have been developed, allowing enthusiasts to distribute their software projects on cartridges for the first time in years. In addition, audio cards have been developed featuring SID chips found on Commodore 64 computers, with SID player/tracker device applications in active development.

Even more recently, the prototype Linux system on plug-in cartridges has been proven at the Chicago Faire 2010 in America, although the intended feature set has not been announced.

Source of the article : Wikipedia