Tandy 1000

The Tandy 1000 was the first in a line of more or less IBM PC compatible home computer systems produced by the Tandy Corporation for sale in its Radio Shack chain of stores.

Overview

The Tandy 1000 was followed by a series of models which appended two or three letters to the name, after a space, (e.g. Tandy 1000 EX, Tandy 1000 SX, Tandy 1000 TX, Tandy 1000 RL, Tandy 1000 RLX). In a few instances, a slash and a number or additional letters were appended to these letters (e.g. Tandy 1000 TL/2, Tandy 1000 RL/HD.)

The machine was geared toward home use and a modest budget, and it copied the IBM PCjr's 16-color graphics (PCjr's graphics were an extension of CGA video) and 3-voice sound, but didn't use the PCjr cartridge ports. As the Tandy 1000 line outlasted the PCjr by many years these graphics and sound standards became known as "Tandy-compatible" or (for the graphics) "TGA" (standing for Tandy Graphics Adapter) and many software packages of the era listed their support for Tandy standard hardware on the package.

Tandy 1000 computers were some of the first IBM PC clones to incorporate a complete set of basic peripherals on the motherboard using proprietary ASICs, the forerunner of the chipset. All Tandy 1000 computers featured built-in Tandy video hardware with color graphics (CGA compatible with enhancements,) enhanced sound, game ports compatible with those on the TRS-80 Color Computer, an IBM-standard floppy disk controller supporting two drives, and a parallel printer port, all integrated into the motherboard. This is in addition to the hardware standard on the IBM PC, PC/XT, and PC/AT motherboards: keyboard interface, expansion slots, memory subsystem, DMA, interrupt controller, math coprocessor socket. (Hard disks were high end, not standard, equipment for home computers until the late years of the Tandy 1000 line, explaining the absence of an integrated hard disk controller from most Tandy 1000 motherboards.) An IBM PC, XT or AT would require at least 4 expansion cards for similar hardware: one video graphics adapter card, one floppy disk controller (FDC) card, one serial and parallel port card, and one sound card with a joystick port. (A third-party multi-IO card might merge the ports and FDC onto one card.) Therefore, the 5 XT slots of the original Tandy 1000, 1000 TX, 1000 SX, and similar models remained available for other hardware, making them equivalent or better than the 8 slots in IBM's XT and AT models (which had 8 slots because the original PC's 5 proved inadequate.)

Most Tandy 1000 models also featured line-level sound and composite video outputs so that a standard television could be used as a monitor, albeit with much poorer video quality than using a computer monitor. Some machines had a port for a "light wand". (Said port on the 1000 SX model is labeled "Light Pen".) Unlike most PC clones, several Tandy 1000 computers had MS-DOS built into ROM and could boot in a few seconds. Tandy bundled DeskMate, a graphical suite of consumer-oriented applications, with various Tandy 1000 models.

The original line was equipped with the Intel 8088 CPU, which was later extended to faster clock speeds and also the 8086 and 286 processors. Tandy 1000s (at least all early models) used Phoenix BIOS. Common models of the machine included the Tandy 1000, 1000 EX, 1000 HX, 1000 SX, 1000 TX, 1000 SL, 1000 RL, and 1000 TL.

For most Tandy 1000 models other than the compact EX and HX that did not come already equipped with a hard drive, Tandy offered hard disk options in the form of "hardcards" that were installed in one of the computer's expansion slots and consisted of a controller and drive (typically a 3.5" MFM or RLL unit with a Western Digital controller) mounted together on a metal bracket. Although this arrangement provided a neat physical coupling between the controller and the disk, single-sector internal transfers and dependence on the speed of the host machine to transfer data to memory meant that a trial-and-error approach was still needed to set the disk interleave correctly to ensure optimum transfer rates. Even then, transfer rates could be as low as 40kB/sec for 8088 and 8086 machines.

Eventually (in the early 1990s,) Tandy Corporation sold its computer manufacturing business to AST Computers, and all Tandy computer lines were terminated. When that occurred, Radio Shack stores began selling computers made by other manufacturers, such as Compaq.

elected Tandy 1000 Models

Tandy 1000

The original Tandy 1000 was a large computer almost the size of the IBM PC, though with a plastic case over a steel lower chassis to reduce weight. The original Tandy 1000 featured a proprietary keyboard port (using an 8-pin DIN connector) along with 2 joystick ports (using 6-pin DIN connectors) on the front of the case. The rear featured a digital monitor connector (a standard 9-pin female D-shell compatible with CGA/EGA monitors), an RCA-style composite video-out connector, a single RCA-style monophonic line-level audio connector, a port for a light wand, and a proprietary edge-card connector used to attach a parallel printer. The original Tandy 1000 came standard with one internal 5.25" double density floppy disk drive, with an additional exposed internal bay usable for the installation of a second 5.25" disk drive (available as a kit from Radio Shack). 128k of memory was standard, with the computer accepting up to 640k of total memory with the addition of expansion cards. MS-DOS 2.11 and DeskMate 1.0 were included with the system.

Tandy 1000 HD

The original Tandy 1000 (and many other models,) like most home computers sold at the time, did not have a hard disk drive. The Tandy 1000 HD was essentially an original Tandy 1000 with a hard disk option factory installed. The factory hard disk had a capacity on the order of 10 or 20 MB.

Tandy 1000 EX

The Tandy 1000 EX was designed as an entry-level IBM compatible personal computer. The EX was a compact computer that had the keyboard and 5.25" floppy drive built into the computer casing. The 5.25" drive was accessible from the side of the computer, on the right hand side. The EX was marketed as a starter system for people new to computing, and sold for $1000.00 from Radio Shack in December of 1986.

Specifications for the EX model included an Intel 8088 7.16MHz (switchable to 4.77MHz) CPU, 256KB RAM, built-in keyboard, CGA video resolution, and one built-in 5.25" floppy drive.

Tandy 1000 HX

The Tandy 1000 HX, released in 1987, was designed as an entry level IBM compatible personal computer. The HX was meant as the successor to the EX. Like the EX, the HX was a compact computer with the keyboard built into the computer casing. The computer came with an Intel 8088 CPU, 256 kilobytes of memory, and had one 720k 3.5 inch disk drive on the right side of the machine behind the keyboard. HX computers came with MS-DOS 2.11 built into the ROM. Deskmate 2 was included with the HX.

The computer's memory could be expanded to 640k. This would be accomplished by placing a memory expansion card, which came with 128 kilobytes, in the expansion slot and adding another 384 kilobytes in memory chips to this board. Contrary to popular belief, the expansion cards were compatible with the 8-Bit IBM slot standard, except for the physical connector. Called "Plus cards" and built by Tandy, they used a pin attachment instead of the slot used by the IBM bus, allowing them to be smaller than standard IBM XT cards. Multiple Plus cards were stacked rather than connected to separate motherboard connectors, also saving space. Radio Shack eventually sold an adapter card that allowed the installation a of "Plus Card" into an 8-Bit IBM slot, such as those in the larger Tandy 1000 models. There were three card positions available in the computer case. In addition to the 5.25" drive bay of the EX model, there was another 3.5 inch drive bay in the computer case. On the back of the machine there was a port which allowed a user to connect an external 360 kilobyte 5.25" or 720 kilobyte 3.5" floppy disk drive unit, available from Tandy. There was also a port to connect a printer.

The 1000 HX did not come with a hard drive, and Tandy Corporation did not manufacture fixed disks for this type of computer. However a number of third party vendors made fixed disks for the HX available for sale.

The settings on the computer could be changed so that instead of looking in ROM for DOS at bootup that it would go to the floppy drive instead. Most versions of MS-DOS worked with the 1000 HX, including DOS 3.x, and some later versions. There was a quirk in the DOS 4.0 environment that prevented that version of DOS from working with Tandy 1000 HX computers.

Tandy 1000 SX/TX

The Tandy 1000 TX was very similar to the Tandy 1000, having an external keyboard and similar casing. The most major difference was the use of an 80286 CPU; otherwise, it was nearly identical to the Tandy 1000, including the unique parallel port edge connector. Despite the 80286 processor, it was still an XT-class PC, not an AT-class PC, as it adapted the 80286 to operate over the same 8-bit data bus as previous Tandy 1000 models, and had 8-bit XT-style expansion slots. As such, it could not operate in 80286 Protected Mode or perform 16-bit memory or I/O transfers in one bus cycle, but it did benefit from the higher speed of the 80286 and its other added instructions in Real Mode. The TX had a 3.5" internal floppy disk drive, with an optional additional internal 5.25" floppy disk drive. It contained ports for two joysticks in the front along with the keyboard, and included a volume control with a headphone jack on the front. The back had all of the same ports as the Tandy 1000, except that the light wand port was replaced with a 9-pin standard D-shell RS-232 serial port. The memory size was 640k (upgradable to 768k, with the added 128K devoted to video*) and the computer came bundled with Deskmate. The SX was identical to the TX except it used a 7.16 MHz 8088 processor, had 384k of memory (upgradeable to 640K on the motherboard,) came with either one or two 5.25" internal floppy disk drives, had the light pen port instead of the RS-232 serial port, and lacked the volume control and headphone jack. All original Tandy-provided internal floppy disk drives for the 1000 SX and TX were double density drives.

* Unlike the IBM PC, PX/XT, PC/AT, and all compatibles, the Tandy 1000 series (except possibly for late models) used part of main memory as video memory, as the IBM PCjr did. Expanding the TX's memory to 768K ensured that more memory would be available in the 640K of the memory space allocated by IBM for main memory (for programs and their data).

Tandy 1000 SL, SL/2, TL, TL/2, TL/3

The Tandy SL and TL series of computers were updates of the SX and TX respectively. Aside from having a redesigned case, the SL and TL each offered an improved video chip (capable of a 640x200 resolution, 16-color screen mode), on-board Hercules Graphics Card compatible monochrome video offering 720x350 resolution, and an improved sound circuit featuring an 8-bit mono DAC/ADC. The latter device, which became known as the "Tandy DAC," was functionally similar to sound devices which connected to the parallel port (such as the Disney Sound Source), but unlike those devices it supported DMA transfers and could sample at frequencies up to 48 kHz. While the Tandy DAC's features compared favorably to those offered by Creative's 8-bit Sound Blaster audio cards, it never gained the same level of market acceptance as the Sound Blaster did, perhaps because it was only available on the motherboard of a Tandy 1000.

The Tandy 1000 SL and SL/2 feature an Intel 8086 processor running at 8 MHz. The 8086's 16-bit bus and slightly higher clock speed gives the SL models a small but definite performance advantage over the earlier 8088-based Tandy 1000s. The SL came with 384k of RAM preinstalled, whereas the SL/2 offered 512k. Both machines can be expanded to 640k, although only 576k could be used by the operating system.

The Tandy 1000 TL and TL/2 use 8 MHz Intel 80286 processors, whereas the TL/3 uses a 10 MHz 80286. These computers had 640 kilobytes of memory preinstalled, with an option for an extra 128 kilobytes to be installed for use as video memory for the onboard ETGA (Enhanced TGA, the "Enhanced" referring to the added 640x200x16 color mode) video hardware. It is therefore impractical to expand the onboard memory beyond 640 KB if a VGA graphics card is installed.

Since the TL series are XT-class machines, it is impossible to install or use extended memory (XMS), although expanded memory (EMS) can be used in conjunction with an 8-bit LIM EMS memory card. Nonstandard expanded memory cards could be used with compatible software.

The SL and TL were also shipped with MS-DOS 3.3 and DeskMate 3 in ROM, and featured an EEPROM memory chip to store BIOS settings (which enabled similar functionality to today's CMOS NVRAMs, so that startup options could be saved). The machines could also run 'normal' MS-DOS 3.x, 5, and 6 and Windows 2 and 3.0, albeit in real mode. In common with many PC Clones of the era, MS-DOS 4 was problematic and generally avoided.

Tandy 1000 RL, RL/HD, RLX, RSX

The Tandy 1000 RL/RLX/RSX series were slim-line desktop home computers. The RL and RL/HD featured a 9.56 MHz 8086 processor, 512 KB of RAM (expandable to 768 KB to provide 128 KB for video), smaller keyboard and mouse ports (which were similar to the PS/2's ports but not directly compatible), a bidirectional parallel port, and the SL's enhanced graphics and sound. The RL/HD also included a built-in XT IDE hard drive.

The RLX was the 'mid-range' offering of the RL line. The RLX featured an 80286 processor and the same 8-bit ISA slot(s), XT IDE hard drive interface and sound chip as the RL, but had an NCR VGA graphics chip instead of the usual Tandy video. Also, the RLX featured a high-density, 1.44 MB 3.5" disk drive. The RLX offered 512KB of memory preinstalled, which could be expanded to 1MB. (The hard drive version came with 1MB preinstalled.)

The RSX offered a 25 MHz 80386SX processor, two 16-bit ISA slots, AcuMos SVGA video, an AT compatible IDE interface and fully PS/2 compatible keyboard and mouse ports. It was a major deviation from the Tandy 1000 design, sharing only the sound chip (which still features the Tandy DAC) in common with earlier 1000's, and being, by virtue of its 16-bit bus architecture, an AT-class rather than an XT-class PC. In this, it can be compared to the Tandy 3000, which was Tandy's full IBM AT clone (with a multithousand dollar retail price.) The RSX came standard with 1MB of RAM, which could be expanded up to 9MB.

External links

* [http://support.radioshack.com/productinfo/ProductResults.asp?Name=Tandy_Desktops&ID=001001001 Radio Shack Tandy Computer Support] , the official support site for Tandy Computers ( [http://support.radioshack.com/productinfo/ product search page] )
* [http://www.oldskool.org/pc/tand-em/ The Tand-Em Project] , a Tandy 1000 emulator project
* [http://www.oldskool.org/guides/tvdog/ Tvdog's Archive] , Major archive of Tandy 1000 programs and documentation
* [ftp://ftp.robertstinnett.com Tvdog's Mirror Archive] , FTP Mirror Site for Tandy 1000 programs and documentation
* [http://www.oldskool.org/shrines/pcjr_tandy Oldskool Shrine to the PCjr and Tandy 1000]
* [http://r.webring.com/hub?ring=tandy1000 Tandy 1000 Webring]

References