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S-100 Utility board (RAM, ROM, UART, parallel, RTC, keyboard, cartridge, etc)


Veteran Member
Dec 21, 2006
Hi! A quick update on the S-100 Utility board. I have four prototype boards and three volunteer builders for build and test phase.

http://n8vem-sbc.pbworks.com/w/browse/#view=ViewFolder&param=S-100 Utility

Since the initial version, I've added a serial port and an RTC. This should be a fairly useful board for S-100 builders as well as for MSX2 compatibility.

If you are interested in volunteering for the initial build and test please contact me. The project requires a working S-100 system.

It also requires experience with S-100 and MSX2 as well as a solid knowledge of their inner workings.

The initial prototype board will likely be quite rough and require significant modification to get working.

I think it is unlikely it will work "right out of the box" and will require significant modification.

Thanks and have a nice day!

Andrew Lynch

A quick update on the progress of this S-100 Utility board. My goal is to
create a board that accomplishes two goals:
1. provide complete MSX hardware compatibility when paired with the S-100
Z80 CPU board and S-100 VDP (to be released soon)
2. provide a general purpose SRAM + IO board that can be used to bootstrap
a basic S-100 system.

At the moment, working with Dan and Alexandre, I have a prototype ready for
review. Basically this board is the guts of an MSX computer minus the
TMS9918 (V9938), AY-3-8910, and CPU. It has 32KB boot ROM and 32KB SRAM in
"slot 0", an expansion cartridge port for "slot 1", 64KB SRAM for "slot 2",
and an expansion port for "slot 3". It uses an 8255 PPI for a really
interesting memory bank switching controller and Matrix ASCII keyboard

The board provides general purpose IO including: 16550 UART,
Centronics-like (not PC compatible) parallel port, Matrix ASCII keyboard
interface, cassette control interface, and MSX Cartridge and Expansion port

Please note this design can be completely separate from MSX and still be
useful. For instance, it could boot from the ROM and load CP/M into a 64KB
SRAM memory similar to how the N8VEM SBC V2 does now. The MSX
compatibility is completely optional and the board would make for a useful
8-bit ROM, RAM, serial port, and parallel port board on its own.

Ideally we could make this a group project like the S-100 VDP board. After
three rounds of prototype boards, thanks to Leon and John, the board is
approaching a useful video and sound board. The S-100 Utility board would
make a great complementary board and I think it would be worthwhile.

I know we've discussed and even attempted design of a basic 8 bit memory
and IO board in the past but so far nothings come of it. Maybe this is our

Please let me know if you would be interested in participating. I have a
preliminary schematic and PCB layout already. It sorely needs review by a
knowledgeable eye to ensure the logic is right for S-100 proper operation.
I will post a version on the Wiki if it will help.

Thanks and have a nice day!

Andrew Lynch