19 Nov
2001
19 Nov
'01
11:52 a.m.
I have that manual (98-422A) and that is the correct one for the
SBC-202. I think Intel just gave the 202 name to that board set when it
was bought for integration into an application.
I am anxious to try to troubleshoot this, but I'm not sure how to go
about it. So far all I have tried to boot the MDS. It does select the
correct drive and load the head. After a pause of about one second the
Interrupt 2 light (on the cpu board, so it is coming from the multibus)
lights solid and the boot code in the MDS system rom returns a
nondescriptive error message "disk error". When it works correctly (two
weeks ago) the interrupt 2 light would pulse (very lightly illuminate)
during read. Now it comes on solid. I believe that Int2 is the signal
from the controller boards signifying end of operation.
FWIW, this seems to be the exact failure mode I've seen in every one
I've had fail. And I have three of them to experiment on, if that
helps. They work ok one minute, then the next they are bad. Nothing in
between. And when I had one good set of boards, the other two sets
definately had the interface board bad. I could make any of the three
channel boards work with my one good interface board. That is until the
last interface board failed.
I just read through the manual tonight, but I still need help with a
direction for shooting it. I was thinking that I should code a simple
routine (in hex since that is all I can think of to load memory in this
machine) to try to read somewhere on the disk and see what error code is
returned. I would guess it will be CRC error.
Note to list: Should we take this private or do you all want to see it?
Tony Duell wrote:
[Intellec FDC Channel board]
--
Dave Mabry dmabry(a)mich.com
Dossin Museum Underwater Research Team
NACD #2093
The purpose of this post is to see if there might
be someone on this
list who would be able to advise me on a strategy for troubleshooting it
(Tony Duell?) Better yet, but I'm not going to hold my breath on this
Oh, what the heck, I've got the manuals to hand. Or at least I've got
some manauls to hand. The most appropriate one is 'Intellec Double
Density Diskette Operating System Hardware Reference Manual', order
number 98-422A. I can't find the name 'SBC-202' anywhere on any of the
manuals, so this might not be 100% applicable.
The interface board described in that manual seems to have 5 separate
sections on it :
Read Data clcock recovery/sync
CRC generator/checker
Write data encoder
Disk drive control/status signals (basically ports from the microcoded
machine on the other board)
Bus control (for DMA transfers, mostly, I think).
My first idea would be to find out which block was malfunctioning. Does
the FDC card appear on the bus at all? Can you select a floppy drive and
move the head around? What goes wrong if you try to read something?
Since this board contains a fair amount of analogue circuitry (the read
data separator phase-locked loop), it's possible that the only thing
wrong with it is that that the oscillator in said loop has drifted way
off frequency and the loop can no longer lock. But don't start tweaking
things without doing some tests.
Do you have the hardware manuals? My manual contains a reasonably good
theory-of-operation chapter which explains what's going on on that board.
-tony