Platform / Tandy 1000

In the early 1980s, Tandy Corporation, the parent company of Radio Shack, wanted a sequel to their successful line of TRS-80 home and business computers. For the home market, Tandy had released the Color Computer in 1980 while the TRS-80 line soldiered on for the business market. However, at the same time, the market for IBM Personal Computer clones was booming. Tandy's first attempt at an x86-based, MS-DOS compatible computer was the Tandy 2000 in 1983, which had, on paper, a number of improvements over the original IBM 5150 PC and the 5160 PC/XT, including using the 80186 CPU, a software-redefinable character set, multi-color high resolution graphics^note 640×400, with 8 colors out of the 16 RGBI colors, and quad-density floppy disk drives, but the 2000 flopped, since it failed to be truly IBM PC compatible.

In March 1984, IBM's new PCjr showed a lot of promise with its then-advanced multimedia capabilities. Less than a year after its release, the PCjr was considered a huge flop due to its high price tag and poor performance when compared to the competing Commodore 64 and Atari 8-bit line, a terrible chiclet keyboard, over-reliance on proprietary hardware combined with a clunky sidecar expansion bus, and limited compatibility with most existing IBM PC software, especially those requiring more than 128K of memory and/or direct memory access. That didn't stop Tandy; in November 1984, Tandy released the Tandy 1000, a clone of the PCjr with a number of improvements to achieve near 100% PC/XT compatibility with 8-bit ISA expansion slots^note Card lengths were limited to 10.5 inches (267 mm) or shorter, rendering full length (13 inches/330 mm) cards physically incompatible due to the 1000 series smaller case sizes; the all-in-one EX and HX use semi-proprietary expansion cards which are electrically compatible with the ISA bus, more memory and direct memory access^note The original model and the all-in-one EX and HX lacked a built-in DMA controller, but one could be added via a memory expansion card, factory hard drive support, and a better keyboard.

Back then, Radio Shack was a household name, and their marketing clout made the Tandy 1000 the hit the PCjr never could be. The 1000's success led to it having a number of follow-ups throughout The '80s; it also attracted game developers, who codified the Tandy's variation on the PCjr graphics and sound systems as the "Tandy Graphics Adapter" or "TGA", helping establish MS-DOS as a game platform and shifting the computer game market in the U.S. from the Commodore 64 to IBM PC compatibles in the second half of the 1980s. Game publishers widely supported Tandy graphics and sound through the early '90s. Later versions of the 1000 added a 16-color, 640×200 mode, integrated Hercules Graphics support, and sample-playback capability.

Unlike the IBM PC and many clones of the period, which relied on multiple expansion cards for basic functionality such as the disk controllers, video output, and parallel and serial ports, most of the Tandy 1000's I/O was integrated onto the motherboard using proprietary ASICs^note application-specific integrated circuit, which helped to reduce costs compared to the IBM PC and most clones; the Tandy 1000's ASIC design was also a precursor to the modern day chipset. Additionally, the tight hardware integration of the Tandy 1000 made producing any Tandy 1000-compatible sound card or display adapter for other systems extremely difficult, if not practically impossible. As with nearly all IBM PC clones, the Tandy 1000 series used MS-DOS as its operating system; however, Tandy bundled the DeskMate operating environment with the Tandy 1000 to give the computer a graphical user interface as well as basic functionality out of the box with programs such as a basic word processor, calendar, calculator, and address book. On later models, Tandy also had DOS and DeskMate boot from ROM for faster startup.

Tandy eventually introduced an entire line of PC compatibles inspired by the 1000, going all the way up to the huge and expensive Tandy 5000, an IBM PS/2 clone with Micro Channel slots. By the early 1990s, the Tandy 1000s were displaced in favor of newer designs from the likes of Compaq and Packard Bell with 32-bit 386 and 486 CPUs, VGA video, Ad-Lib/Sound Blaster audio, and Microsoft Windows sold in other mass merchandisers; Tandy eventually sold their manufacturing facilities to AST Research, and started marketing Compaq PCs for a while.

Specifications

Similar to the Apple ][ series, the Tandy 1000 had several revisions over its lifespan.

Tandy 1000

• Introduced 1984.
• Intel 8088 at 4.77 MHz.
• 128 KB RAM, expandable up to 640 KB.
• Lacked an onboard DMA controller; however, one could be added via a memory expansion card.
• Optional hard drive via hard card, 10 or 20 MB.
• 3 8-bit ISA expansion slots.

Tandy 1000A

• Introduced 1985.
• Revision of the original model, which fixed bugs and added an 8087 math co-processor socket as well as the ability to scan expansion cards for bootable ROMs

Tandy 1000 SX

• Introduced 1986.
• Successor to the original model.
• Intel 8088-2 at 7.14 MHz.
• 384 KB RAM, expandable to 640 KB.
• First model to integrate a DMA controller on the motherboard.
• First model to support the installation of an EGA or VGA card by disabling the onboard Tandy graphics.
• Optional hard drive via hard card, 20 MB.
• 5 8-bit ISA expansion slots.

Tandy 1000 EX

• Introduced 1986.
• Cost-reduced variant of the SX, and at one point, the least expensive IBM PC-compatible available.
• All-in-one desktop, using the keyboard wedge form factor similar to the Apple ][ series or the Commodore 64.
• Intel 8088-2 at 7.14 MHz.
• 256 KB RAM, expandable up to 640 KB.
• Lacked an onboard DMA controller; however, one could be added via a memory expansion card.
• Proprietary edge connector to add a second external floppy disk drive; a 5¼" model was available at launch while a 3½" version was released later. The connector supplies power to the disk drive, making it compatible only with the EX and later HX.
• No official hard drive support; however, third-party options did exist.
• 3 PLUS expansion slots. These slots are electrically compatible with the 8-bit ISA bus, but use a pin header connector rather than a card edge connector. It is possible to use regular ISA cards with an adapter, but this is limited to half-height, short length cards due to case constraints.

Tandy 1000 TX

• Introduced 1987.
• Enhanced variant of the SX, using the 80286 CPU rather than the 8088.
• Intel 80286 at 8 MHz.
• 640 KB RAM, expandable up to 768 KB (640 KB for DOS, 128 KB for video logic).
• First model to come with a 3½" 720 KB floppy drive standard rather than a 5¼" 360 KB floppy drive; however, the TX has two 5¼" bays.
• Optional hard drive via hard card, 20 MB.
• 5 8-bit ISA expansion slots.

Tandy 1000 HX

• Introduced 1987.
• Successor to the EX.
• Intel 8088-2 at 7.14 MHz.
• 256 KB RAM, expandable up to 640 KB.
• Lacked an onboard DMA controller; however, one could be added via a memory expansion card.
• The side-mounted 5¼" 360 KB floppy drive was replaced with a front-mounted 3½" 720 KB floppy drive and a second bay to support a second 3½" floppy drive. The external floppy drive connector is still present.
• No official hard drive support; however, third-party options did exist.
• 3 PLUS expansion slots.
• Last model to support CGA composite video output; all subsequent models would support RGBI only^note except for the RLX and RSX, which supported VGA, but the SL's, TL's, and RL supported installing an EGA or VGA expansion card.
• First model to embed portions of MS-DOS in ROM, allowing the computer to boot to a DOS prompt without a bootable floppy disk.
• First model to save BIOS settings to an EEPROM chip, accessed through a specialized setup program on floppy disk, rather than using DIP switches.

Tandy 1000 SL and SL/2

• Introduced 1989.
• Successor to the SX.
• First model to include Tandy Graphics II and the PSSJ audio ASIC, which added 8-bit sample playback support to the existing SN76489 PSG.
• First model where the on-board floppy disk controller, printer port, and serial port can be disabled.
• Intel 8086 at 8 MHz.
• 384 KB (SL) or 512 KB (SL/2) RAM, expandable to 640 KB.
• Optional hard drive via hard card, 20 MB.
• 5 8-bit ISA expansion slots.
• The SL features two 5¼" drive bays, while the SL/2 has two upper 3½" bays and a single lower 5¼" bay.
• Tandy-specific keyboard connector replaced with a standard XT-compatible DIN connector; the keyboard also adopts the IBM Model M 101-key layout.

Tandy 1000 TL, TL/2, and TL/3

• Introduced 1989.
• Successor to the TX.
• Intel 80286 at 8 MHz (TL and TL/2) or 10 MHz (TL/3).
• 640 KB RAM, expandable up to 768 KB (640 KB for DOS, 128 KB for video logic).
• Optional hard drive, 20 MB. The TL/2 and TL/3 have an integrated XT-IDE hard disk controller on the motherboard while the TL requires a separate hard disk controller card.
• 5 (TL) or 4 (TL/2 and TL/3) 8-bit ISA expansion slots; on the TL/2 and TL/3, the fifth expansion slot is omitted due to the integrated hard disk controller.
• TL/3 floppy disk controller includes support for 3½" 1.44 MB high density drives, but shipped with 720 KB double density drive(s) standard.
• Last model to support 5¼" drives. Also the last full-sized desktop model.

Tandy 1000 RL

• Introduced 1990.
• Slimline desktop, roughly half the height of the SL and TL series.
• Successor to the HX.
• Intel 8086 at 9.54 MHz.
• 512 KB RAM, expandable up to 768 KB (640 KB for DOS, 128 KB for video logic).
• Optional XT-IDE hard drive, 20 MB. Due to the smaller chassis, the RL can only accommodate either a single floppy drive plus a hard drive or dual floppy drives.
• 1 8-bit ISA expansion slot.
• First model to use a standard DB-25 parallel port rather than the Tandy-specific (but electrically compatible) edge connector.
• First model to use PS/2-style 6-pin Mini-DIN connectors for the keyboard and mouse. While physically compatible with PS/2 keyboards, most PS/2 keyboards use the AT protocol rather than the XT protocol, which the 1000 series (except for the RSX below) requires. A 5-pin DIN XT (or XT-AT switchable) keyboard can be used with an AT-to-PS/2 adapter, since both keyboard standards use the same pinouts.
• Last model to have true Tandy 1000 compatibility.

Tandy 1000 RLX

• Introduced 1991.
• Upgraded version of the RL.
• Intel 80286 at 10 MHz.
• 512 KB RAM, expandable up to 1 MB (640 KB for DOS, 384 KB for extended memory).
• Tandy graphics replaced with VGA with 256 KB VRAM.
• Optional XT-IDE hard drive, 20 MB or 40 MB.
• 1 8-bit ISA expansion slot.
• 720 KB double density 3½" floppy drive replaced with 1.44 MB high density drive. The RLX's floppy disk controller does not support double density drives.

Tandy 1000 RSX

• Introduced 1992.
• Unlike the rest of the Tandy 1000 series, which were 16-bit XT-class machines, the RSX was a 32-bit AT-class machine, making it a Tandy 1000 In Name Only.
• Intel 80386SX at 25 MHz.
• Only model to support Windows 3.xx.
• 1 MB RAM, expandable up to 9 MB with two 30-pin SIMMs^note Supports 1 MB or 4 MB modules; however, both slots must use matching modules.
• SVGA with 256 KB VRAM onboard, expandable to 512 KB.
• Supports AT-IDE hard drives up to 504 MB in capacity.
• 2 16-bit ISA expansion slots.
• While the PSSJ audio ASIC was still present, its I/O addresses were altered, breaking compatibility with supported games unless patched.

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