PERQ T2

Tony Duell ard at p850ug1.demon.co.uk
Wed Aug 1 17:46:37 CDT 2007


[For the benefit of others who may be wondering 'how the heck does he 
know that', I've received (and answered) a couple of private e-mails 
about this particlaur PERQ. Since it's been taken to the classiccmp list 
now, I'll reply here]

> 
> I've got a PERQ T2 which was working until
> fairly recently. It seems the boot track on the
> hard disk (Micropolis 1303) is damaged in some
> way so the PERQ wont boot.
> 
> I have a floppy boot disk which is known to be good,
> but unfortunately the PERQ T2 doesnt want to boot
> from floppy. SHIFT-A doesnt work on the T2.

Shfit-A (or any other key combination) does exactly the same thing to the 
ROM bootstrap on a T2 as on every other classic-PERQ. Namely nothing. 
>From what I can see from the ROM source listings (jsut ask me if you want 
commented sources to the T1 or T2/T4 bootstraps), the sequence is :

1) CPU initial diagnostics. If these fail, the machine goes into an 
endless loop, the DDS will be <10

2) Attempt to boot from the PERQlink (16 bit parallel port on the OIO 
card), floppy drive nand then hard disk in that order.

The machine conventionally loads VFY and SYSB from the appropriate disk. 
VFY is more extensive system tests (including main memory), SYSB is the 
bootstrap. Now, IMHO the POS SYSB is broken-as-designed because, in the 
abscence of a keypress, it tries to load the first interpretter microcode 
from the hard disk (even if SYSB iteself was loaded from the flopyp 
drive). IIRC the PNX boot does things properly and loads the rest of the 
system from the decvice that it was loaded from.


> 
> Is there any way I can force the T2 to boot from
> floppy?

On a correctly working PERQ, putting a disk in the floppy drive and 
pressing the reset button will at least load the initial microcode from 
the floppy. Holding down shift-A will get the rest of POS to load from 
the floppy too. Yes, that does work on a T2.

Nwo, I seem to rememebr that a T2 has to have a hard disk that will go 
ready -- that is assert the READY/ signal on the control connector, 
before it'll try to boot from floppy. The drive doesn't need to contain 
any valid data, it doesn't even need to be formatted. I think a T1 will 
boot from floppy even if the hard disk is totally dead.

One thing worreis me a lot about what you've told me, or rather what 
you've not said. You assume that the boot track is corrupted, with AFAIK 
no real evidence for this. You will find I don't take kindly to people 
who make random assumptions, and nor for that matter do PERQs.

Also, you don't know if the Z80 system is working. If it isn't, the 
machine cna't boot from floppy, since the FDC is connected to the Z80 I/O 
procesor. So for that matter is the SIO that takes in data from the 
keyboard, so if the Z80 system is malfunctioning, it'll not read the 
keyboard either.

There are several things I would do. Firstly, I'd check signals at the 
hard disk conntectors (standard ST412 inteface in a T2). Is said drive 
going ready? 

Then, if you have, or can borrow, a logic analyser, ask me for the boot 
listhing. Connect said analyser to the mcirocode address lines (on the 
lowermost test connector at the front of the CPU board). We can then see 
if it's trying to boot from floppy, if it's trying to boot from the hard 
disk, or what. 

> 
> Just a few other points, when switched on the HD
> LED remains on all the time. I'm assuming the

I think that's right. The drive is selected all the time (unless you have 
a second drive installed), so the LED is on. Actually, the drive is 
squirint out the bitstream of the current track, but the machine might 
well be ignoring it :-)

> drive is attempting to seek the boot track. Ultimately
> the PERQ times out with code 013 which means HD
> time out.

It seems to me an more a hardware failure of the hard drive (as opposed 
to a corruption/checksum error)

One question. IIRC you told me this is a Micropolis 1300-series drive. 
Those are notorious for a decayed rubbre bumper inside the HDA which 
means the heads don't load, the drive doesn't find track 0, and then 
fualts. IIRC, the drvie spins down when this happens. Do you know if your 
drive keeps on spinning?

-tony



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