diagon_swarm wrote on 2020-09-30, 16:51:
Just a question after seeing the video - will PS/2 Model 30 boot if the BIOS is not set and the RTC battery is dead?
Yes, just like the "working" model he obtained later did. That one behaved (except for the broken video output) just like a PS/2 model 30 with flat battery. It does not use a standard AT-style RTC, but a MM58167A instead, which only has very few bits of RAM. It doesn't seem to need RAM because memory size is auto-detected on boot, there is only one kind of floppy drive (3,5", 720K) to support and most likely only one kind of hard disk was envisioned by IBM - not that I ever heard about an IBM PS/2 model 30 with an integrated hard drive, though. The three supported monitor types are also auto-detected by the BIOS, so this doesn't need configuration, too. If the battery is flat or the keyboard is missing, you get two beeps after the memory test. I am surprised how quick after power on the two beeps were heard, but maybe the SIMMs in that machine are of the 64KB variety, so the machine has 256KB instead of 640KB. Compare the time-to-beep (assuming no cuts) on the broken machine (5.5s) to the time-to-beep on the nearly working machine (15 seconds). The first machine clearly didn't test 640K of RAM. It took the second machine around 8 seconds to count from 256KB to 640KB, which is still less than the 9.5s difference, so the double beep likely occurred after just testing the base 128K onboard RAM.
Taking a look at the PS/2 BIOS 61x8939/61x8940, a double beep can only occur after the POST completes with error, along the "press F1 to continue" message. If the onboard RAM is bad, the machine dies without any beep. Possibly the POST detected a memory error quite at the beginning of the expansion RAM.
While re-watching that part of the video, I compared the mainboard with the PS/2 model 30 mainboard, and it seems nearly, if not completely identical. At 3:51, you can guess the part number of the mainboard. It seems to look like 61x8825 - and this is a common PS/2 model 30 mainboard indeed! The ISA riser + battery card also looks the same as my one, and the part number shown in the video, 61x8863 also is a common PS/2 model 30 part. The part numbers on my PS/2 model 30 differ, it seems to be from an older batch. When I next have access to the machines, I will take a peek at the newer PS/2 model 30 I have and compare part numbers again. The part number on the floppy drive matches my PS/2 model 30.
So the executive workstation seems to consist of some well-known PS/2 parts (planar + bus board + floppy drive) in a sleek compact case with a special power supply built to fit the form factor of that case, and the internal monitor power supply. Quite a shame that the component that got damaged in this video is one of the components you can't find in your garden variety model 30 computer.
The ASCII art for "time and date not set" is nice (it's a clock with no hands, but four flashing question marks in the center), and the animated ASCII art for "insert floppy disc and press F1 to continue" is even nicer. You get to see both of them if you power the machine on, it lost time and no floppy is inserted.
As the 8-bit guy stated, the one he got had a color monitor (and obviously a 15kHz model), whereas the other computers might have had the 31.5kHz monochrome monitor. I don't hear the 15kHz whine on youtube videos on my hardware, and I am admittedly too lazy to caputure the sound with a spectrum analyzer to find out whether the non-working system had the 15kHz signal others observed at the kind-of working system.
