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IBM PS/2 Model 30

It's unusual that it has a white power switch. All the other regular Model 30s (not 30-286) that I've seen have a red switch.

I know sometimes around 1989-1990 both Tandy and IBM changed from red power switches and reset buttons to white, because according to a new government standard, red could only be used for emergency stop buttons/switches.

Maybe it just so happens that most Model 30s were made before that change, while this late-production one was after.
 
vwestlife said:
It's unusual that it has a white power switch. All the other regular Model 30s (not 30-286) that I've seen have a red switch.

I know sometimes around 1989-1990 both Tandy and IBM changed from red power switches and reset buttons to white, because according to a new government standard, red could only be used for emergency stop buttons/switches.

Maybe it just so happens that most Model 30s were made before that change, while this late-production one was after.
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I think you may be right about the change for later units .... I have taken a good look and can see no evidence that the switch has ever been dismantled, so I have to assume it's original to this unit....
 
I have a question about the 8086-based Model 30. How did it support PS/2 mice when P2/2 mice typically used IRQ12, which wasn't available on 8086 and 8088 systems? Does anybody have a clue? Maybe the use of IRQs in the mouse driver was optional? I remember reading somewhere that the Microsoft Bus Mouse card (InPort?) had a dip switch or jumper setting that allowed it to work without needing an IRQ. Polling only by hooking the timer interrupt, I guess?

Or maybe the 8086-based Model 30 had a secondary PIC (and therefore an IRQ12) too?
 
Hmmm, I found a possible answer here:

Indeed, the IBM PS/2 model 30, running on an 8086 processor, has Real Time Clock services, but not with the same hardware. The model 30 uses a VLSI gate array the keyboard controller, mouse controller, real time clock and interrupt controller. There is only one interrupt controller (compatible with the 8259A PIC chip in the PC XT and AT computers), but all functionality is jammed inside the 8 lines of the PIC by connecting the keyboard, the mouse and the Real Time Clock to IRQ 1.
Click to expand...

Interesting. So if I understand correctly, IRQ sharing was employed here, and PS/2 mice apparently use IRQ 1 on the 8086-variant of the Model 30, as opposed to IRQ 12 in later PS/2 models.

Ah yes, and these sources appear to confirm that:
Alright, that solves that mystery then. :)
 
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