The motherboard is well documented in the web but there are several variants of this motherboard, some of which behave quite differently (e.g. see WriteBack cache).
My board has revision 2.4 which doesn't support 486DLC processors with the original bios.
I found on this Russian side the bios of the motherboard revision 2.7 and tried it out.
It works for me without any troubles and adds support for 486DLC processors :o)
Performance
The BIOS has an option "Cacheable RAM Address Range" which must be set to the size of the mounted memory (in my case 32MB) - otherwise the performance would be poor...
With the right setting the motherboard gives good results:
All measurement results are documented here.
Write Back cache
On the board is an empty 24 pin socket (U32) for a chip which saves the write-back dirty flags.
According to the jumper table a 16kx4 SRAM is needed.
I tried out the Motorola MCM6290P (Cypress CY7C166 should be an alternative) and got from 2 to 4 percent more cache performance (depending on the used processor).
The hard disc write test, on the other hand, benefits much more from the write-back mode:
I read somewhere: chips with 22 pins (e.g. Cypress CY7C164 or IDT7188) should also work if the chip is aligned to pin 1 of the socket.
I tested it with a P4C188 from Pyramid Semiconductor but I didn't see any improvements. I assume, the statement above is not true for all revisions...
Facts
| Manufacturer / Type: | PcChips M321 Rev.2.4 |
| Year of manufacture: | probably end of 1992 (PCB was manufactured in week 40 in 1992) |
| Bios-String: | 30-0100-001437-00101111-060692-PC CHIP-F |
| Bios: | Revision 2.4 |
| Revision 2.7 | |
| Chipset: | PCCHIPS CHIP5 4L04F1282 (28/1992) |
| PCCHIPS CHIP6 4L04F1666 (26/1992) | |
| Manual: | Found on the rainbow-software.org server |
Summary
Strong points:
- Option for Write-Back cache with performance improvement
- 32MB RAM possible
- Comfortable board size with a lot of ISA slots
- Support of 486DLC processors (after BIOS update)
Weak points:
- Fixed CPU frequency (needs crystal change)
- Active cache strategy (Write Through, Write Back) isn't mentioned by the BIOS
falk.richter*at*yandex.com
Last update: May 22, 2021