Content created by Sandy. Edited by Major Tom.
PS/55 Model 5580 is the Japanese equivalent of PS/2 Model 95 (8595).
Basically there are 2 variants of this model. One is the -Yxx model which uses processor complex similar to the PS/2 Type 1 "K" board. The other is the -Wxx model with complex derived from the PS/2 Type 2 "H"/"L" board. The BIOS P/N is different when compared to the original PS/2 boards.
They were entry server models.
Model 5580 uses the 8595 1S1P planar. No distinctive differences.
Models 5580-Y/W use the older long SCSI /A with cache adapter (SPOCK 6451018). Even if the newest SPOCK is used, 5580 can't use hard drives larger than 1GB to IML. In order to unlock full potential of the newest SPOCK, 8595-J Type 3 complex or any Type 4 complex should be used.
Can 5580 Take Regular PS/2 Complexes?
The answer is "Yes". But you have to use the corresponding *PS/2* reference and diag disks to configure the system. Some of my friends managed to configure a Type 3 DX-50 complex and Type 4 "N" and "Y" boards on 5580. No reports regarding the older PS/2 Type 1 and Type 2 platforms.
Some tips for 5580/5560
Refdisk ver. 1.21 is what you should have. If you have more than 16 MB of RAM in total, you need a reference diskette ver.1.21 to let the system recognize the installed RAM correctly. (ver. 1.11 for 5561)
Under Win95 the system may report only 16 MB of RAM even if you have more memory installed. To solve this replace HIMEM.SYS that came with Win95 with the one from PCDOS J7.0. This symptom is commonly observed on the other 486 IML machines, but not on EIDE machines such as 5551-R/L and 5530-L.
F/W SCSI-2/A can't be used alone in 5580 with the original complex.
Not sure about this issue. It is told that the PS/55 BIOS doesn't contain the
required SCSI code (maybe).
Server Models Other Than 5580
9585, 8595-J with Type 3 M platform and 9595 N/P/Q are the same
as the corresponding PS/2s. All models were originally equipped with Japanese
ref/diags, but they will accept English ref/diags too.
Overclocking is, err... evil, especially for PS/2 and PS/55 machines. What we expect from them is stable operation and reliability. So it is not recommended to change the the CPU clock oscillator with a faster one. International Business Machines does not expect clock modifications. I was just MAD. It's probably better to keep your MCA box *clean*. But anyway here we go...
Japanese Type 1 J with 25 MHz OSC for 61-W0 will take 30 MHz OSC without any trouble. But all other complexes will not work with faster OSC in place of the originally equipped one (to be more precise, it is possible to use 35 MHz OSC in place of the 33 MHz one for some complexes). If you change the base clock, you need to modify the BIOS as well, in most cases. Without BIOS modification, system will hung up during POST with error code 102.
I didn't (well actually I still don't) have any knowledge of how to read or write BIOS. Mr. Sugiura, one of my friends, who knows about BIOS reading/writing, examined BIOS of the 5561-W1x complex and he MODIFIED the BIOS so that the 61-W could boot without the 102 error. According to him, there are several lines indicating jump to the 102 error section during the POST routine. He couldn't determine which line exactly was triggering the error with the modified system clock. So he rewrote all lines that were jumping to the 102 error section. I don't know if his modification includes any bugs or not. But, so far, BIOS ROM with his modification works fine. At least in my systems. He kindly examined another models' BIOS ROM and burnt new EPROMs for me, and for other members of the forum.
List of models and complexes modified by Mr. Sugiura:
More of this story is available HERE.