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
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
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
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?
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