XT Motherboards

The IBM PC and XT were cloned/copied by hundreds of companies in the late 80s and early 90s. This page is dedicated to looking at a number of these motherboards. Most aren't easily identifiable due to their ubiquity and the fact that the original manufacturers would sell their designs to a number of resellers.

Note that when powering an XT or compatible motherboard using an AT power supply, many boards follow the IBM XT standard which requires that pin 2 of the P8 power connector disconnected. This is a red wire that provides +5V DC in the IBM AT. Some XT boards will fail to boot if this wire is connected and the power supply may click continuously.

 

DTK PIM-TB10-Z

This board from Datatech Enterprises Co. (aka DTK) follows the design of the IBM PC-XT in both size and layout. It has the standard eight 8-bit ISA expansion slots, socketed DRAM chips in the lower-right corner (18 x 256 kbit chips in Banks 0 and 1, a total of 576 KB plus 48 KB to their left in 6 x 64 kbit chip), ROM sockets in the middle, and CPU/math-coprocessor sockets in the top-left.

It supports "Turbo" mode whereby the 10 MHz Intel 8088 typically runs at 10 MHz, but will slow down to 4.77 MHz when the turbo switch is off. The DIP switches just to the left of the CPU are most likely configured the same as you would on a real IBM XT. Click here to see the standard IBM PC and XT DIP switch settings and how to configure them.

The two large chips in the top-centre are an Intel P8255 PPI (Programmable Peripheral Interface) chip and below it a P8237 DMA controller. Below these are the two ROM BIOS slots (one populated) - the original PC and XT had the BIOS firmware "split" across two chips - one identified as "high" and the other identified as "low". Most XT clones have an 8 KB BIOS held in a single 2764 ROM chip, like this one.

User Manual Another Picture

DTK PIM Turbo 10-V01

Another XT board from Datatech Enterprises Co. (aka DTK). This one is quite early, as the P8/P9 power connectors are round pins rather than rectangular which are seen on later AT boards.

Like to IBM 5150 and 5160, this provides additional ROM sockets with only one in use which is the ROM BIOS. It has the full complement of eight 8-bit ISA slots for expansion, and is an AT-sized board. It looks like 4 banks of memory are available.

 

Juko ST 8088

The Juko ST motherboard is a mid-size XT motherboard, offering eight 8-bit ISA slots for expansion. It has an ASIC (Application-Specific Integrated Circuit) which replaces a lot of discrete components, giving the board higher reliability. This one has an NEC V20 running at 8 MHz.

Known BIOS Revisions: Juko ST BIOS v2.30

It has More pictures here: 1 2 3 4 5

 

VIP TXM/10-II

The VIP motherboard is a full-size XT motherboard, offering eight 8-bit ISA slots for expansion. It is about the size of the original IBM XT motherboard, and as such has all the discrete logic above the memory banks.

It has More pictures here: 1 2 3 4

 

 

Zeta "Peter-10" XT

A late XT board from 1991, this one came from a London-based computer wholesaler called Morgan Computers. The board is really small, about the size of a modern-day Micro-ATX motherboard, and a very neat layout.

It has eight 8-bit ISA slots and is running a Sony-branded NEC V20 at 8 MHz. A single ROM chip can be seen at the bottom marked "P10" (this appears on the boot screen also), and the large single ASIC single-chip chipset is a Proton PT8010AF. This I believe is a knock-off of the Western Digital Faraday FE2010A.

Towards the lower left corner, 640 KB of DRAM chips is installed.

 

Twin Turbo XT

This late XT board design is very common. Like the Zeta above, this board is small, about the size of a modern-day Micro-ATX motherboard.

It has eight 8-bit ISA expansion slots, supports Intel 8088 or NEC V20 CPUs, and is populated with 640 KB of DRAM chips (12 x 1Mx1 Fast Page 100ns). Note the power connector is the old AT-style, but has circular pins instead of the more common 'blade'-style pins. Slightly at odds with other small XT boards, this one doesn't come with an 8087 math coprocessor socket. The chip to the right of the 8086 CPU socket is the keyboard controller (NEC80C42).

 

X Golden Board

This is an early XT clone motherboard from 1985. Just as with the IBM XT, it has eight 8-bit ISA expansion slots. In the top-left you can see the socketed CPU and above it an empty slot for the 8087 math coprocessor.

A bank of eight ROM sockets (5 populated) exists in the middle of the board - the top one is the main BIOS ROM. The original IBM PC and XT catered for some applications to be available on ROM chips, but the concept never really took off, probably due to the high cost of ROM chips as opposed to floppy disks.

640 KB of DRAM chips fills the bottom-right of the board. At the top-centre (above the ROM bank) is an Intel P8237 DMA controller. The chip above it is most likely a Programmable Peripheral Interface (PPI) chip.

User Manual

 

Super-10 Turbo XT

An interesting board, as this comes with 640 KB of DIPP RAM on a daughter card that plugs into the motherboard. There is provision on the board for another bank of memory (see the pads in the lower right corner), but no RAM chip sockets.

More pictures here: 1 2 3 4 5 6 7

 

 

Super Turbo-III

This model from an unknown manufacturer follows the ever-popular XT board layout. It has the old-style AT power connectors (round pins, not blades). This board appears to be missing most of its chips though - no 8088 CPU, no ROM BIOS, and no keyboard controller. DMA controller also?

More pictures here: 1 2 3 4 5 6 7 8 9 10

 

MB-1100 Turbo XT

The MB-1100 is another of the newer XT boards with a lot of the discrete components replaced with an ASIC (Application-Specific Integrated Circuit), which gives it higher reliability.

One interesting thing about this board's design is the main CPU being down by the ASIC, not up near the power connectors like most boards.

More pictures here: 1 2 3 4 5 6 7