Tandy 1000 platform

Hardware theme

Tandy was highly "MS-DOS compatible" but not a perfect match to changing IBM specs over time. Many companies made 'Tandy 1000' editions of their games


The first video game about Tandy 1000 platform was released in 1982.

RufusPro Software, Sierra On-Line and Symbiotics has published most of these games

CPU: Intel [email protected] ([email protected] in later models, still later [email protected])
RAM: 128K (shared with 2k-128k video, expandable to 640K, 9MB for later models)
OS: IBM PC-DOS 2.10 in 64K? ROM (will also boot from cassette, disk, Later models came up to DOS 3.3. Last models used 132K EEPROM for combined ROM and BIOS and DOS 6.22 could be burned in)
Text modes: 40×25x16, 80×25x16
Graphics 320×200×4, 640×200×2, 160×100×16, 160×200×16, 320×200×16, 640×200×4, Later 640×400×16, still later 800x600x16.
Ports: CGA+/EGA+ D-9 (TGA, later ETGA, still later HD-15 SVGA),RGB, composite video, TV, line-out audio, wired keyboard 8-pin DIN, two joystick 6-pin DIN (8-pin mini-DIN in later models, nearly standard DB-15 ports in last models), printer (edge-card parallel port. external 5½, 3¼, and hard drives were later created for this port. this port was later replaced with a standard, bi-directional parallel port), cassette port (removed on later models), lightpen (later replaced with an D-9 RS-232 serial port), PS/2 type keyboard and mouse ports (not PS/2 compatible, but the last models were PS/2)
Expansion: 7 XT-bus pin slots, 1 external XT-bus pin slot (later models added two 16-bit ISA slots).
Media:5¼ DD 360k disk drive (optional 2nd 5¼ DD disk drive), (3½ DD 720k disk drives were available in later models), (later models came with a 10-20MB hard drive, still later models included an IDE connector for up to 2 IDE drives)
DeskMate 1.0 in ROM (up to 3.0 in later models)

Real world differences between Tandy PC compatibles, the PCjr and mainline IBM-PCs lead to some platform specific games that are more than just in a different box or have a different label.
Cartridges are only usable on the PCjr. This is not just a media issue, The cartridges had a reserved address space in memory. When Tandy failed to deliver a cartridge option, this memory was considered available by developers making Tandy specific games. This memory space has different uses entirely on IBM-PC. The PCjr required hardware to 'plug' the cartridge memory 'hole' but a Tandy 1000 could accomplish the same thing entirely in software.
Tandy machines with the added expense of cartridge ports were planned. But the console videogame crash of 1983 hit Sierra, Activision, and Imagic hard. These were the only companies making PCjr cartridges. The most dedicated Tandy supporter, Sierra, had hired 100 new employees, opened a new headquarters, and invested in 100 new cartridge games just as the crash occurred. They were soured to cartridges and vowed never again (just a few cartridge versions were reluctantly licensed out to other companies after that). Mattel was ramping up for massive PCjr cartridge roll-out as well when the crash prompted them to prioritize and cancel PCjr support. Spinnaker made cartridge versions of their educational titles. These of course were already available on disk before the PCjr/Tandy were conceived of and educational software rarely drives expensive hardware upgrades the way games do (especially as Spinnaker was a "budget software" company). Tandy had lost all the cartridge makers and didn't see where adding cartridge support was worth the handful of games that were just going to be republished or were already published on disk anyhow. As far as I am able to tell, no cart games later published on disk are the same game. They were updated.

Joystick circuitry timing was altered slightly in the Tandy 1000 to work with inexpensive Tandy Joysticks (originally for the TRS-80). Joystick control will not work properly or fail entirely for some platform specific games.

Floppy drive hardware is controlled differently between the 3 systems. If a game tries to do anything with a disk without using the system's own operating system then it will fail. Booting the "correct" operating system for the game won't help, including bootloaders, it is a hardware issue. Bootloaders on UVL are sometimes a different entry because of hardware, not simply because they are bootloaders. In fact, a 'wrong' operating system will succeed if used to run a game on the right hardware. Games written in assembly language sometimes attempt direct disk access. DRM often attempts direct disk access.

BASIC is different between the three systems. Similar to the floppy drive issue since some games will try to look directly at the PCjr cartridge or the IBM-PC ROM which contained different versions of BASIC. Or it may simply try to do anything hardware specific. Note that later IBM-PCs did not even have BASIC in the ROM. DRM often has this issue (even in games not written in BASIC). Some BASIC games have no hardware issues and fail because of differences in the BASIC dialect included with the system. This can be overcome by manually loading the correct dialect of BASIC from disk. However, hardware can still indirectly cause issues since the correct BASIC version itself may not like the wrong hardware (common with unofficially extracted ROM BASIC, or official versions of BASIC claiming to match a ROM BASIC).

Memory mapping between the three systems is different. Tandy has at least 39 differences. The BIOS handles this invisibly when games or operating systems are addressing memory via a BIOS. But if a game bypasses the BIOS and uses direct memory access, it could fail for any one of these 39 differences.

Keyboards are different between the three systems. On a technical level, any key required can be typed on any system. Even Tandys lacking Function keys, numeric pad, and other extended keys. Alternate keystrokes are used to type the missing keys. This is done through the BIOS for each system. Buuuut, many games don't use the BIOS to read the keystokes. Assembly code action games almost universally bypass the BIOS for keyboard control. Even something as universal as an INKEY loop in BASIC will bypass the BIOS. "Press F2 to start" may not work, making the game runable but literally unplayable on the wrong hardware.

Video hardware is built into the Tandy motherboard, there are two distinct standards unique to Tandy video. One of this close enough but not identical to PCjr but the other is not emulated by any IBM-PC cards. The Tandy BIOS does not allow for switching off the on-board video nor directing video to an expansion card (it must be hacked). Most Tandy models only accept 8-bit expansion cards. Tandy expansion slots are physically distinct from IBM-PC and PCjr slots (which are even more useless). Tandy uses shared system RAM as Video RAM. The shared Video RAM can be especially incompatible and was an attractive option for developers who wanted to animate with more frames on Tandy than they could on IBM-PC regardless of which card was used on the IBM. VGA & EGA are especially problematic on Tandy hardware. Adapters to add 8-bit expansion cards to Tandy computers are available. Adapters to add 16-bit expansion cards to 16-bit Tandy computers are available. These do not automatically overcome the BIOS of earlier models so additional software workarounds must be used. CGA is not even the same on Tandy. The BIOS translates CGA just fine but games that try to write directly to the VRAM (for alternate resolutions, alternate colors, faster animations) will fail on Tandy 1000. So in addition to distinct Tandy video modes, there is a distinct Tandy CGA mode for some T1K specific games. Tandy CGA mode used a 16 color palette and could show 16 colors on screen via palette tricks. Some DOS game with "Tandy graphics" mode will actually only run in Tandy graphics mode when on a real T1K and not on a video card that emulates it. Late model SVGA Tandy hardware (rare) solves many of these issues, but not all of them.

Some Tandy 1000 specific games will not function with Tandy Video mode & Tandy Sound mode separately. The software will only run with both together. These were not designed to be run on anything else than a Tandy 1000. This means some DOS games cannot be enjoyed with both the best graphics and best sound options. Examples would be EGA or VGA game where Tandy sound was the most realistic best sound option (MT-32 sound is of course best, but not realistic) so EGA or VGA would have to be sacrificed to get the best sound. The parallel port in early Tandy models was not bi-direction further limiting options for sound. Another way would be where the a CGA only IBM-PC user would want Tandy sound but can't use that sound mode because it also requires using Tandy graphics. Likewise, an IBM-PC user might have a card that emulates Tandy graphics but not a sound card that emulates Tandy sound (or emulates '4 voice' extremely badly using the PC Speaker)

The Real Time Clock functions differently between the three systems. As far as I know this is not a game breaker but it can cause game altering effects.

Expanded & Extended Memory functions differently between the three systems. Tandy 1000 games that require expanded and/or extended memory are specifically Tandy 1000 games.

Network Cards must be 8-bit on Tandy 1000 machines. Chances are a Tandy 1000 game using any kind of network play is a Tandy 1000 game.

Sound Cards must be 8-bit on Tandy 1000 machines. Like video, Tandy has its own sound hardware that can be emulated by other cards and has a second sound mode (Tandy DAC) that is not emulated anywhere except the platform specific PS/1 audio card. T1K machines will accept 8-bit sound cards. Some models will also do some 16-bit sound cards but only 8-bit sound modes will produce sound. The parallel port in early Tandy models was not bi-direction further limiting options for sound.

Tandy Sound hardware integrates the PC speaker as part of the system. Tandy sound could actually be called "4-voice" since the speaker could be used for one of the voices (if quality of the 4th voice was not an issue). Some T1K games did exactly this. When I say integrated, I don't mean just the BIOS. Rather, the sound components where connected in the circuit board and with soldered components in addition to the hard-wiring in the IC chips. Needless to say, the results of playing a Tandy 1000 "4 voice" game on an IBM-PC that used the real speaker would produce quite a dissonant noise. Later IBM-PCs and compatibles used a speaker cable that could be detached from the speaker and plugged into an add-on sound card instead. This was not necessarily a fix as many sound cards treated speaker audio as a stand-alone alternative to be passed directly to the audio out port and would not play speaker sounds along with any other modes. 4 voice T1K games would be missing an entire voice on an IBM-PC.

Serial ports for IBM XTs have a bug that does not exist on Tandy hardware. A later standard that works without the bug is not available for Tandy hardware. This can be a problem for games that expect the bug.

IDE & SCSI on Tandy 1000 must be 8-bit. It did not come with these interfaces, as TRS-80 specific MFM and RLL interfaces were a vast cost reduction all around. Hard drive compatible MFM and RLL themselves were an afterthought as Tandy considered hard drives too expensive and unnecessary for their target customers. This is not a problem on an operating system level but hard drive games doing anything 16-bit specific are incompatible. Some exceptionally evil DRMs will fail for hard drive installed games. Chances are, a Tandy 1000 specific game that installs to hard drive is actually a Tandy 1000 specific game.

High Density Floppies on Tandy 1000 is well like that 500-horsepower Mercedes minivan. Cool, but, why? and who actually owns one? Yet, game developers put games for Tandy computers on High Density Disks (who actually owned a Tandy with an HD floppy controller installed?).

  • Fully Tandy game in Tandy box (it may incidentally run on non-Tandy)
  • Fully Tandy game in universal box (might have Tandy Sticker) (it may incidentally run on non-Tandy)
  • MS-DOS game in a Tandy box or universal box with Tandy sticker (This is just an ordinary DOS game, no Tandy graphics or sound, boasting Tandy compatibility)
  • MS-DOS game in with additional "Tandy" noted on the box and a separate Tandy version on the media(disk). There's also fully Tandy game on the media.
  • MS-DOS game and Tandy game in the same box on separate disks or flippy disk.
  • MS-DOS game in with "Tandy" boot disk. There could be a separate executable on either disk or it is just a pre-configuration to run the DOS executable on Tandy. Either way, the normal/DOS game disk(s) are read after booting the Tandy disk
  • Fully MS-DOS game with a setup/installer to configure for Tandy graphics and/or Tandy sound. This is he most common Tandy compatibility option. This can be indicated with the display-tga and spu-tandy tags.

The original Tandy 1000 is basically an 8-bit XT-class IBM PCjr clone with enhancements. But the Tandy 1000 lacked the PCjr's cartridge bus. PCjr cartridges cannot be run on a T1k.
Some games were made in Tandy editions that likely did not run on IBM-PCs (especially if there was also an 'IBM version'). Other games were IBM-PC based and had settings to make it 'Tandy Compatible'. Rarely would a PC game run on a T1k without configuring. "Tandy sound" and "Tandy Graphics" settings were very popular for games before the 486 era for PC games that also ran on the Tk1. Tandy computers with 486, Pentium, or later CPUs and upgrades available, never gained popularity. "Tandy compatible" games virtually disappeared before the Pentium era.
The Tandy 1000 was much more successful than the PCjr, in fact the PCjr was discontinued soon after release but Tandy 1000 models continued for decades. The final models that sold in noticeable numbers were 16-bit 386 based.
PC Enterprises' GameMaster card was created to 'upgrade' the existing PCjr to be Tandy 1000 compatible. There is also a mod to accomplish this upgrade for users willing to do some soldering. The joystick ports are not PCjr compatible. The PCjr used different proprietary game port than a standard PC. Tandy computers had ports for cheaper-than-IBM-PC Tandy peripherals, not so much to lock-in customers rather to save them money. Tandy Coco, TRS-80 and Tandy 1000 used 6-pin DIN game ports and later models of the T1k used 8-pin mini-DIN ports (backward compatible using a 6-pin adapter). Adapters to use standard PC joysticks were available for the T1k and PCjr. Later T1k models used DB-15 gameports that were almost standard (basic 2-axis-2-button joysticks work, hats and extra buttons might cause problems, hats and extra buttons will probable not work even if they don't cause problems). TRS-80 joysticks are 100%. The T1k lacked the PCjr's infrared port for which no accessories were ever released. Both systems use the PCjr expansion bus with 1 external 'sidecar' port. However, the IBM used edge-card slots while the T1k and PCjr used pin sockets. Adapters were common. the T1k has 8 (generally 5 usable) while the PCjr had less since video, drive controllers, and other functions were built-in to the T1k mother board while the IBM often needed as many 5 cards to do what the T1k did on the mother board. 8-bit ISA cards could be used with adapters and 'sidecars'. Later models added 2 standard 16-bit ISA slots. Standard D-15 PC gameports can be added with expansion cards and PC joysticks generally then work with any T1k joystick compatible game. Later models included 2 nearly standard DB-15 game ports. The T1k will accept the same math co-processors as PC/XT and PC/AT motherboards. The first T1k motherboards had no integrated hard disk controller as hard drives were considered high-end and the T1k was a budget PC, like the PCjr was designed to be. The enhanced T1k sold for less than the PCjr. MS-DOS was built into the ROM which combined with no hard drive effectively limited DOS compatibility although it could boot other version of MS-DOS from disk (up to 6.22) and run booterloader games. MS-DOS 4.0 was sabotaged by Microsoft and would not function on most T1k models (like many PC clones, the targets of the sabotage). Ironically, all IBM PC-DOS 4.0 versions could be made to work. It had audio, composite video, RGB, and TV out jacks. Video and TV out was of very poor quality. The TGA/ETGA port was a standard D-9 port that worked on any CGA/EGA monitor. Despite later models having a 80286 CPU, the bus and memory of the T1k remained 8-bit and it would not run in protected mode (it was only windows compatible in real mode). The last models were fully 16-bit. The 8-bit presented the largest barrier for compatibility. XT-bus VGA, 8-bit ISA VGA, or 16-bit ISA SVGA cards could be added, but this was mainly to run IBM games not T1k games. The T1k had no dedicated video memory and used the standard RAM. This allowed higher resolutions and colors that other IBM compatibles of the day. But this took memory from the main program and video updates were slower. Later models dedicated some of the RAM to video but this was just reserved RAM rather then video memory. DOS programs that needed 640K required a T1k with 768k of memory so the video would have the minimum 128k. However, this could be used as an advantage. Swapping memory banks used for video could animate graphics as fast as a monitor refreshed (faster actually, but that was useless). IBM-PC hardware could not match that. This of course would be describing a feature of a Tandy specific game. Non-standard cards could add memory via the XT-bus, including XMS and EMS, but these were usually made for specific software and not general use. OR standard 8-bit LIM EMS memory could be used, but standard memory and non-standard LIM would conflict with each other, only one or the other could be used. Later models used EEPROM for ROM and BIOS that allowed for upgrades (or downgrades) to the built-in operating system and applications. The EEPROM models finally allowed users to customize the boot process so they could leave bootable media in without being forced to boot it. Bottom line, Tandy computers could do all common computers tasks cheaply and most any other task if more money was spent.


4=Button 1
5= +5V
6=Button 2

Sierra was hired to create games to show off the PCjr's capabilities. They created King's Quest and began working on many other games for the system. Then IBM dropped support for the PCjr. Sierra was concerned that this might bankrupt them, but they were rescued by Tandy 1000 that could run their PCjr games.

The Tandy could boot to MS-DOS prompt in under 2 seconds. Upgrades were offered that decreased this even more. Some T1k models could be underclocked as slow as 4.77z for backward compatibility.

Related groups

Tandy SPU, Tandy Graphics Adapter, Tandy DAC, Tandy Video II, IBM PCjr platform

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