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View Full Version : Recipe For a Homebrew PC-XT Compatible Motherboard



NicolasF
February 27th, 2016, 04:23 PM
I've been thinking about building an XT motherboard that will boot DOS and be able to run games and applications.
I made this list as a starting point but I'm not sure about certain things.
At this stage I'm not interested in coding a BIOS so I would like the board to use an existing generic BIOS or maybe the 5150 original one.

8088 Processor (Minimum mode)

RAM 512Kb SRAM

ROM 32Kb Flash

8237 DMA
- Channel 0 (Not used, no DRAM refresh)
- Channel 1-3 (Used by diskette, hard drive, video card?, ISA port?)

8253 Timer
- Out 0 Timer interrupt
- Out 1 Unused?
- Out 2 Speaker

8255 PPI
- PortA Keyboard code input?
- PortB Unused?
- PortC Unused?

8259 PIC
- IRQ 0 Timer interrupt
- IRQ 1 Keyboard?
- IRQ 2-7 Free to be used by other device

NMI (Not sure what it does)

Memory map and I/O ports (compatible with PC-XT)

BIOS - I'm guessing it will need some minor changes to make it boot.

Will this setup be able to work? What do you think?

Thanks!

HoJoPo
February 27th, 2016, 05:14 PM
You could build a PC clone with this kit: http://www.mtmscientific.com/pc-retro.html

All the hard parts are already done...

Plasma
February 27th, 2016, 07:37 PM
You may be interested in Sergey's XT (http://www.malinov.com/Home/sergeys-projects/sergey-s-xt).

MarsMan2020
February 27th, 2016, 09:56 PM
You may be interested in Sergey's XT (http://www.malinov.com/Home/sergeys-projects/sergey-s-xt).

One of the RetroBrew Computers (new home of what used to be N8VEM) members has all of the boards you would need available - ISA backplane, Xi 8088 board, ISA SVGA, XT-CF-IDE, and Floppy - http://www.retrobrewcomputers.org/doku.php?id=boardinventory

3pcedev
February 27th, 2016, 11:16 PM
Why only 512kb of SRAM? I would go for 640k as you will no doubt run into something that needs a lot of RAM. Personally I would probably shoot even higher for >640k and run UMB's.

NicolasF
February 28th, 2016, 04:52 AM
My goal with this proyect is to have a better understanding of how the PC-XT works at a chip level, so I'm not interested in copying an existing board.