Texas Instruments TI-994A

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1979 TI-99/4 withRF modulator, optional Speech Synthesizer, keyboard overlays, and a cartridge

$525 (equivalent to $1,400in 2017)

TheTexas InstrumentsTI-99/4Ais ahome computer, released June 1981 in the United States at a price of $525 ($1,400 adjusted for inflation). It is an enhanced version of the less successfulTI-99/4model, which was released in late 1979 at a price of $1,150 ($3,900 adjusted for inflation). Both models include support forspritesand multi-channel sound, some of the first home computers to include such custom hardware, alongside theAtari 8-bit familyalso introduced in 1979.

The TI-99/4 has acalculator-stylechiclet keyboardand a character set that lacked lowercase text. The TI-99/4A added an additional graphics mode, lowercase characters consisting of small capitals, and a full-travel keyboard. Both use 16-bit processors, making the TI-99/4 series the first 16-bit home computers.

The TI-99/4AsCPUmotherboard, andROM cartridge(Solid State Software) slot are built into the keyboard. The power regulator board is housed below and in front of the cartridge slot under the sloped area to the right of the keyboard. This area gets very hot so users commonly refer to it as thecoffee cupwarmer. The external power supply, which was different according to the country of sale, is a step-downtransformer.

Available peripherals included a 5┬╝floppy disk driveand controller, anRS-232card comprising two serial ports and one parallel port, aP-codecard forPascalsupport, athermal printer, anacoustic coupler, atape driveusing standardaudio cassettesas media, and a 32KBmemoryexpansion card. The TI-99/4 was sold with both the computer and amonitor(a modified 13Zenithcolor TV) as Texas Instruments could not get itsRF modulatorapproved by the U.S.Federal Communications Commissionin timecitation needed. The TI-99/4A did ship with an RF modulator.

In the early 1980s, TI was known as a pioneer inspeech synthesis, and a highly popular plug-in speech synthesizer module was available for the TI-99/4 and 4A. Speech synthesizers were offered free with the purchase of a number of cartridges and were used by many TI-written video games (notable titles offered with speech during this promotion wereAlpinerandParsec). The synthesizer uses a variant oflinear predictive codingand has a small in-built vocabulary. The original intent was to release small cartridges that plugged directly into the synthesizer unit, which would increase the devices built in vocabulary. However, the success of softwaretext-to-speechin the Terminal Emulator II cartridge cancelled that plan. In many games (mostly those produced by TI), the speech synthesizer has relatively realistic voices. For example,Alpiners speech includes male and female voices and can be quite sarcastic when the player made a bad move.

State of the art 16 bit computer system in 1979 a TI-99/4 console, including the rare Thermal Printer.

TI-99/4 PEB or Peripheral Expansion Box

The TI-99/4s original expansion concept was that peripherals would be connected serially to the console and each other, in adaisy-chainfashion. The sidecar expansion units can be connected together in a continuing chain, but can rapidly occupy an entire desktop and cause crashes and lockups due to the large numbers of connectors on the system bus.

This original idea was soon replaced by a system based on expansion cards. Encased in silver plastic but made from sheet steel, these plug into the bulky Peripheral Expansion System (usually known among TI owners as the Peripheral Expansion Box or PEB), an eight slot chassis, containing its own linear power supply and a full-height 5┬╝ floppy bay.2Each card also has its own access light, anLEDwhich would blink or flicker when the card was being used by software. As on the earlierS-100 bus, the section of the power supply that power the card slots is unregulated. Each card has on-board regulators for its own requirements, thus reducing power consumption on a partially loaded PEB and allowing for future expansion cards which might have unusual voltage requirements.

The PEB also carries an analog sound input on the expansion bus. This allows the TI Speech Synthesizers audio to be carried through the console to the monitor. The audio is also carried through theribbon cable(firehose, as TI users often call it) to the Peripheral Expansion System, both allowing the relocation of the Speech Synthesizer to the Expansion box and allowing for the possibility of audio cards offering more features than the consoles built-in sound. No official cards from Texas Instruments ever made use of this line.

Early models (the TI-99/4, identified by its keyboard and(C)1979 TEXAS INSTRUMENTSon the title page) includes a built-in equation calculator, but in the 99/4A ((C)1981 TEXAS INSTRUMENTS) this feature was discontinued. All consoles includesTI BASIC, a strictANSI-compliantBASICprogramming language interpreter which is largely incompatible with the more popular, and frequently imitated,Microsoft BASIC. Later consoles, identified by(C)1983 TEXAS INSTRUMENTS V2.2on the title page, also remove the ability for the system to execute unlicensedROM-based cartridges,locking outthird-party manufacturers such asAtarisoft.

The system has ajoystickport that supports two digital joysticks, which TI referred to as wired remote controllers. The two joysticks are connected through a single nine pinDE-9port which is identical with those used forAtari 2600joysticks but with incompatible pins. Aftermarket adapters were available which allow the use of twoAtari-compatible joysticks.3The computer supports saving to, and loading from, two cassette drives through a dedicated posite videoand audio are output through another port onNTSC-based machines, and combine through an external RF modulator for use with a television.PAL-based machines output a more complex YUV signal which is also modulated to UHF externally.

The TI-99/4 series holds the distinction of being the first 16-bit personal computer.4The TI-99/4A has arunning at 3.0MHz. The TMS9900 was based on TIs range ofTI-990mini computers.

Only theProgram CounterStatus Register, and Workspace Pointer registers are on the chip; all work registers are kept inRAMat an address indicated by the Workspace Pointer. 16 registers are available at any given time, and a context switch instruction which changed to another workspace automatically allows fast context switches compared to other processors which may have had to store and restore the registers. For CPU RAM, the machine has only 256 bytes of scratchpad memory to support the storage of workspaces. This memory is placed directly on the 16-bit bus with zero wait states, making it much faster than any other memory available to the system.

Although the CPU is a full 16-bit processor, only the system ROMs and 256 bytes of scratchpad RAM is available on the 16-bit bus. All other memory and peripherals are connected to theCPUthrough a 16-to-8-bitmultiplexer, requiring twice the cycles for any access and introducing an additional 4-cyclewait state. (This is reportedly due to the failure of a new 8-bit processor being designed by TI for this system, while the 9900 processor was already in production and proven.) A popular user modification in later years involves piggybacking static RAM chips onto the consoles 16-bit ROM chips, allowing a standard 32kB RAM expansion without the wait state and approximately a 30% speed increase for many applications. Applications previously running entirely in 8-bit RAM (both code and registers) can speed up by a factor of two. Most hardware is based on the system clock, not the program execution speed, and the hardware access still runs through the 8-bit bus with the wait states intact, so this particular modification does not affect any peripherals.

By decoding some unused I/O-bits in the console, it is also possible to use the full address range of 64 kB RAM in the machine, by overlaying other memory and/or ports, under I/O (CRU) control. By doing so the console ROM can be copied into RAM, and thus things like interrupt vectors and such could be modified. However, such modifications are not frequent enough to make anyone but the particular modifier himself write any software to use it.

Thevideo display processorin the 99/4 is aTMS9918.5It lacks abitmapmode, which was added in the 99/4A. The VDP in the American 99/4A is the TMS9918A (which gives the machine the A in its name). In the European PAL consoles this is replaced with theTMS9929Awhich also poweredMSXmachines.

A unique feature of these VDP chips is that they contained hardware support for superimposing on-screen graphics over other video signals. Although TI announced a peripheral card called the Video Controller Card which allowed the control of selectlaserdisc players, which could switch between the TIs display and the laserdisc player, thegenlockcapability of the 9918 is disabled in the design of the 99/4A and requires hardware modifications to use.

All accesses to the VDP system are executed 8 bits at a time. Although this affects performance, it made it easier to upgrade the VDP when newer, relatively compatible chips were released byYamaha. Peripherals from Mechatronics, and Michael Becker, simply called 80-column cards include theYamaha V9938VDP which gives the 99/4A a top resolution of 512424 in 16 colours or 256424 in 256 colors. This also increases the VDP memory from 16K to a maximum of 192K, although only software explicitly written for the 9938 take advantage of it.

The unusual architecture of the 99/4 series is documented to be due to the failure of the 9985, an 8-bit processor which was being created specifically for the machine. When it was abandoned, the 16-bit 9900 was selected to replace it, and a great deal ofglue logichad to be added to fit the processor into the existing design, while no changes were made to take advantage of the 9900s strengths.

All TI-99 models, from the earliest TI-99/4 to the unreleased TI-99/2 and TI-99/8, includeplug and playsupport for all peripherals. Device drivers (called Device Service Routines, or DSRs) are built into ROMs in the hardware; when a new card was inserted, it is immediately available for any software which needed or wanted to use it. All device access utilize a generic file-based I/O mechanism, allowing new devices to be added without updating software to use it. The Communications Register Unit (CRU) can address 4096 devices; however, each TI card runs at a hard-wired address on the CRU bus, and so multiple cards of the same type cannot be supported without modification. The only official card known to be modifiable 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-lineBBSeswere being run, using properlyjumperedserial cards, on TI-99/4A systems as recently as the mid-1990s.citation needed

Most hobbyist-created cards released after TIs exit from the personal computer business include switches to set the base CRU address.

The HexBus Interface was designed in 1982 and intended for commercial release in late 1983. It connects the console to peripherals via a high-speed serial link. Though it is prototypical to todaysUSB(plug and play, hot-swappable, etc.), it was never released, with only a small number of prototypes appearing in collector hands after TI pulled out of the market. Several HexBus peripherals were planned or produced. A WaferTape drive never made it past the prototype stage due to reliability issues with the tapes. The 5.25-inch floppy drive also never made it past the prototype stage, even though it worked.6Prototype DSDD disk controllers and Video controllers were also made.7A four-colorprinterplotter, a 300-baudmodem, RS-232 interface, an 80-column thermal/ink printer, and a 2.8 Quick Disk drive were the only peripherals released in quantity, mostly for use with theCompact Computer 40(CC-40). All HexBus peripherals can be used with a TI-99/4A when connected through the HexBus Interface, through direct connection to the TI-99/8, or through direct connection to the CC-40.

The TI minicomputer-inspired architecture of the TMS9900 series means that the Workspace of registers currently in use are stored in main memory. Because static RAM was also very expensive in the early 80s, TI only gave the machines 256 bytes of fast scratch pad RAM where register workspaces could be stored.

The original design for the intended CPU had this 256 bytes internal to the CPU itself, but the 9900 requires registers to be in external memory. Placing this small amount of memory on the 16-bit bus nevertheless helps the performance of the machine (as compared to having registers in 8-bit RAM with a 4-cycle penalty for every access). Some programs, such asParsec, copied short loops of code to this memory to take advantage of the performance.

The sidecar and PE box expansion systems makes possible an official 32kB RAM expansion.8This is not available to all uses for example an Extended Basic program was restricted to using 24kB with the remaining 8kB available for machine code routines.

Third parties provided replacement memory cards for the PEB. For example, Myarc produced 192kB and 512kB cards.9The memory provided by the Myarc cards can be partitioned for use as regular CPU RAM, a RAM disk and a printer buffer.

The Mini Memory plug-in module also contains 4kB of RAM that can be used as a persistent RAM disk (it contained a button cell) or to load a machine-code program.10

It is also possible to add an 8kB supercart or 32kB superspace cartridge via the cartridge slot, which also included the Editor/Assembler GROM. This uses the cartridge ROM space.

Texas Instruments engineers afforded 16kB ofVideo Display Processor(VDP) RAM to the TI99/4As graphicscoprocessor, aTMS9918A. The VDP RAM was DRAM, with the VDP handling refresh. This is expandable to 192kB with the use of aYamaha V9938as a user-designed modification (not a standard upgrade option).

VDP RAM is also used for storing buffers for disk I/O, and variables and code for usersBASICprograms. Hence, the largest BASIC program possible is less than 16kB. BASIC is implemented on the TI-99 series using a secondinterpreted languagecalled Graphics Programming Language (GPL). The GPL interpreter resides in the ROMs and takes control of the machine at power-up, and was very close to the native 9900 machine code, adding instructions to transparently access the different types of memory in the machine and perform higher level functions such as memory copy and formatted display. Users who install memory expansion still need to upgrade to the Extended BASIC cartridge to use it instead of VDP RAM.

The same VDP is used in theMSXandColecoVisionmachines. Further upgrade chips, the 9938 and 9958, were produced by Yamaha based on TIs design. Boards were created that took advantage of these new chips to upgrade the graphics capabilities of the TI-99/4A. The 9938, the more common of the two upgrades, allow 512 424 pixels at 16 colours, or 256 424 at 256 colours. These upgrades are not a simple drop-in and replace; a small board including the replacement VDP and replacement VDP RAM (usually 128kB) is required. In addition, although the chips were largely software-compatible, certain bugs in the ROMs cause compatibility issues with the new chips. One board, the Mechatronic 80-column card featuring the 9938 require that the user press a button when entering TI BASIC.

Graphics Read-Only Memory is another set of memory accessed a single byte at a time through a dedicated memory port, and were auto-incrementing read-only devices. (There is also support in the console for GRAM, simulators for which were created by third parties later.) The vast majority of TI cartridges (Disk Manager 2, Editor/Assembler, TI Writer, most games) use this system, as does the consoles TI-BASIC. Swapping the TI-BASIC GROM with a GROM removed from a favorite cartridge is a popular modification, as is installing several GROMs into one cartridge allowing a multicart, with all included GROMs being available in the boot menu.

Since the standard machine does not allow third party machine language support, programmers found their markets decidedly limited to those users who actually added more RAM to their systems. This limitation was alleviated as the price of 32 kB expansion card and a 4 kB Mini Memory module eventually came down, but by then the market had moved over to other computers.

Some sophisticated cartridges (for exampleParsec,Alpiner, TILOGOTI Extended BASIC) include memory-addressable ROM which was available for machine code, primarily for games or applications which demand the speed of machine code. None of this memory is available to the user. In general, ROM-equipped cartridges may be identified by having 28-pin ICs on the board, while the GROM ICs have 14 pins. A small number of cartridges also include a small amount of RAM (notably those games produced for the Milton Bradley MBX expansion system).

Tigervision developed a unique solution to the memory limitation of the standard cartridge slot; a 24kB cartridge that attached to the side expansion interface, emulating an expansion device. This allowed the company to implement a larger game completely in machine code. Tigervision cartridges using the expansion port includeEspialandMiner 2049er. A third cartridge,Sprinter, is listed in its 1984 catalog but was not released. Exceltec also released two similar side cartridges,Arcturus11andKiller Caterpillar.

Because of the speed bottlenecks (16-to-8-bit bus multiplexer) and the doubly interpreted BASIC, the TI-99 series gained a reputation for being quirky and eccentric, which endeared it to some and maddened others. Many people who had only experienced TI BASIC also considered it very slow, although assembly programs actually manage fairly good speed despite the hardware issues to overcome.

Texas Instruments(1981)Main article:List of TI-99/4A games

Developers created about 100 99/4A games, most published by Texas Instruments.12Some of the most popular wereParsec,TI Invaders,Munch Man,Alpiner,Tombstone City: 21st Century,Hunt The WumpusandCar Wars.

Many TI-developed video games, especially those developed by John Phillips, may be forced intocheat modeby holding the shift key and pressing 838. Terse messages often appear, which may allow the user to move to a different round of the game. InMunch Man, the top screen and top round includes invisible Hoonos (ghosts in thisPac-Manderivative) which travel several times faster than Munch Man. InAlpiner, the player can select which mountain to climb. 838 (with or without SHIFT) inStar Trekgives a random but high level of torpedoes, shields, and warp-drive energy.

InfoWorldcriticized the computers game library as mediocre.12TI discouraged third-party development for the 99/4A, including games, but did not license popular arcade games likeZaxxonorFrogger.1314The company actively promoted the TI-99/4A in educational use (as opposed toAtariandCommodores emphasis on arcade-game action) and learning programs for children comprised a large portion of its software library. But as theApple IIalready had a major foothold in schools, in USA, and was an open architecture that anyone could easily develop for, TI failed to make an impact there.

In 1977 groups within Texas Instruments were designing avideo game console, a home computer to compete against the TRS-80 and Apple II, and a high-end business personal computer with a hard drive. The first two groups merged at TIs consumer products division inLubbock, Texas; the 99/4s (according toWalden C. Rhines) ultracheap keyboard,RF modulator, and ROM cartridges came from the console design. Others within the company persuaded the Lubbock group to use TIs TMS9900 CPU.5

Although TI was much larger than any other personal-computer company when it entered the market in 1979, the $1,150 TI-99/4 was,The New York Timesin 1983 stated, an embarrassing failure.13David H. Ahlstated that it was vastly overpriced, particularly considering its strange keyboard, non-standard Basic, and lack of software.14Adam Osbornereported in July 1980 that despite poor sales TI had raised the price of a complete system to $1,400, making the computer more expensive than the more popular Apple II, which was available for as little as $950. Some dealers, who have offered the complete system (including the monitor) for less than the price of the Apple, have still been unable to sell it, he added.15

Two years after the 99/4s debut, TI released the 99/4A, very similar but with a better keyboard and more expansion options.14By lowering its price and offering rebates TI sold many more computers;13it has been estimated that it had about 35% of the home computer market at its peakcitation needed.

In 1982 TI began aprice warwithCommodore Internationalby lowering the street price of the 99/4A to $200, including a $100 rebate, to compete against the $300Commodore VIC-20. TI spokesmanBill Cosbyjoked how easy it was to sell a computer by paying people $100 to buy one, but the company continued to lose shelf space, as Commodore matched the $200 retail price by December 1982.1314

The president ofSpectravideolater said that TI got suckered byJack Tramiel, head of Commodore.14TI was forced to sell the 99/4A for about the same price as the VIC-20, even though it was much more expensive to manufacture. Although TI and Commodore each owned their ownICfabrication facilities, Commodore created custom ICs to reduce the cost of its computers, while TI continued to useoff-the-shelfcomponents and make only relatively small revisions to their motherboards. Commodore also made other cost-cutting changes including using aluminized cardboard to build RF shields for some of their systems.16The TMS9900 required expensive customsemiconductor packaging;5TI continued to use high-quality components and materials with the unfulfilled hope that the marketplace would recognize it.

By mid-1982Jerry Pournellewrote that TI was practically giving away the TI-99/4A.17An industry joke stated that the company was losing money on each computer, but was making up for it in volume.14The 99/4As list price was $400 that autumn,13but the street price including $100 rebate was about $200. Sales peaked at 30,000 a week in January 1983, but on 10 January 1983 Commodore lowered the price of its computers; the VIC-20s wholesale price was $130. In February TI responded by lowering the 99/4As retail price to $150. In April Commodore again lowered prices, and the VIC-20s bundled retail price reached $100. TI also lowered prices and offered rebates, reducing the 99/4As retail price to under $100; by this time the company was likely losing money on each computer. In early 1983 TI stopped sales for a month to correct a defect, butpredicting in April that the home-computer market that year would be much larger than most industry analysts expectedcontinued production at an annual rate of three million, increasing inventory. In May it began offering the PEB for free with the purchase of three peripherals; by this time TI was using price cuts as the 99/4As primary marketing. In August the company reduced prices of peripherals by 50% and offered $100 of free software; in September, it reduced software prices by up to 43%.131418

TheTimesstated in June 1983 that Cosbys $100 refund joke is no longer funny, and that future options are slim for TI;L.F. Rothschildestimated that the company would only sell two million computers. The low price probably hurt the 99/4As reputation; When they went to $99, people started asking Whats wrong with it?, one retail executive said.13

After losing $111 million after taxes in the third calendar quarter of 1983, TI announced in October 1983 that it was discontinuing the 99/4A, while continuing to sell the-compatible computer.18(TI stock rose by 25% after the announcement, because the companys other businesses were strong.)19With another TI price cut, retailers sold remaining inventory of the former $1,150 computer during Christmas for $49;1420Child Worlds 90 stores almost immediately sold more than 40,000 computers at the price,21and a riot almost broke out at aas shoppers fought over the computer.22Discontinued during thevideo game crash of 1983, the 99/4A became the first in a series of home computers to beorphanedby their manufacturer over the next few years, along with theColeco AdamMattel AquariusTimex Sinclair 1000andIBM PCjr. A total of 2.8 million units were shipped before the TI-99/4A was discontinued in March 1984.citation needed

The TI-99/4A is more sophisticated than the VIC-20, offering more memory and more advanced graphics capabilities. However, a number of elements of its design attracted criticism. All peripherals plug directly into the right-hand side of the unit (unless the user purchased the expensive and heavy Peripheral Expansion Box), which causes the computer to not fit well on top of a desk if a user adds many peripherals besides a tape drive and a printer. In addition, the 48-key keyboard layout does not match that of atypewritervery closely, and there was (at the time) no option for an 80-column display. The keyboard and display limitations made it unpopular forword processing.

TI could not make a profit on the TI-99/4A at a price of $99,23but hoped that selling many inexpensive computers would increase sales of more profitable software and peripherals. Because such arazor and blades business modelrequires thatsuch products be its own,13TI kept strict control over development for the machine, discouraging hobbyists and third-party developers.17ASpinnaker Softwareexecutive said that the 99/4A had the worst software in the business, and Ahl noted that unlike other computers, it did not haveMicrosoft BASIC,VisiCalc,WordStar, or any popular games.14CitingMoney, publisher ofKilobaud MicrocomputingWayne Greenreported in August 1980 that TI planned to have only 100 applications available by the end of 1981, stating that This tiny figure has to put a chill on the whole industry.24Its peripherals cost about twice as much as for other computers.2313TI joysticks, for example, were of poor quality and difficult to find; one reseller reported that its best-selling product was the Atari adapter cable.3

Green said that although his company Instant Software had published hundreds of programs for theTRS-80[and] want to translate as many as possible for use on the TI-99/4, it could not find anyone among more than 1,000 developers in its network who could port software to the computer, adding We understand the problems with the system and the efforts Texas Instruments made to make translation difficult.24Rival companies were much more open with information. The next issue ofKilobaud Microcomputingreported that a Commodore executive promised that the forthcoming VIC-20 would have enough additional documentation to enable an experienced programmer/hobbyist to get inside and let his imagination work.2526IBM released complete software and hardware technical information for thePersonal Computerwhen announcing it in 1981,17stating that the definition of a personal computeristhird-party hardware and software.27

Pournelle in 1982 wrote that because well over half the really good stuff for microcomputers has come from hobbyists and hackers … which TI hadwronglyconcluded that they were … unimportant, it found itself cut off from the mainstream. He believed that TI recognized its mistake and would change.1728The company, however, insisted on itself selling others software, which many developers refused to agree to.13Afterthird-party developersgames for the Atari 2600 became very successful, TI at the June 1983Consumer Electronics Showannounced that only cartridges withTI-licensed circuitrywould work in the 99/4A. TheBoston Phoenixpredicted that most [software developers] just wont bother making TI-compatible versions of their programs.23Pournelle wrote after the announcement that TI once again tells the hobbyists to drop dead.28

No official technical documentation from TI was released until the Editor/Assembler assembly language development suite was released in 1981, and no system schematics were ever released to the public until after TI had discontinued the computer. In addition, the TI-99/4As awkward architecture and nonstandard CPU (as opposed to the6502andZ80which all programmers of the day were familiar with) made it difficult to develop for.

The TI-99/4A maintained acult followingfor years after its death in the marketplace, in part because of its eccentricities, and in part because TI had actively supported a network of user groups during the production of the machine. It eventually came to achieve a cult following among retro-computer hobbyists. In 2004 a Universal Serial Bus (USB) card andAdvanced Technology Attachmentcontroller forfor the PEB were released, and there is still an annual Chicago TI Fair29where people congregate to celebrate the historic TI-99 family of computers. Third-party devices such as expanded memory cards, improved floppy controllers, and hardwareramdisksare very stable and popular additions to the machine, although there are no current known sources for these devices. In the early 1980s, abulletin board systemTIBBS), developed by Ralph Fowler ofMarietta, Georgia, running on the 99/4A became very popular and brought many users together. Also, a number ofemulatorsfor the TI-99 exist today for PC-based systems.

There was also a portable sibling to the TI-99/4A.