lane@cs.dal.ca (John Wright/Dr. Pat Lane) (07/24/89)
I have a strange problem with a floppy disk drive - perhaps someone
out there can help me.
I have a 6/10MHz (1 ws) 286 clone w 1 Meg RAM (150 nsec), Phoenix 286 BIOS
ver 3.01, a noname herc clone video card (MTS 11727 - is that the brand/
model no.?), a WD1003-WA2 hard/floppy disk controller, a Seagate ST225 hard
disk, and a Shugart SA455 floppy disk drive (360K). I originally had a
Panasonic JU475 1.2Meg drive but replaced it with the Shugart, which came
out of a Tandy SX1000, when it packed it in and I happened to have the
Shugart handy - I'd been planning to stick it in as a second drive anyway.
The problem is that if the machine is at 10 MHz, the drive will at some
point stop reading any disk put into it, coming back with "Drive not ready".
Rebooting cures the problem for a short while but it soon returns. However,
with the system at 6 MHz, it never occurs. I've been running at 6 MHz since
I noticed this.
The problem never occurred in the middle of a write operation (and thus never
munged a disk, thank heaven). I don't know if I was just lucky there.
Another possible factor: When I had the 1.2Meg drive I often got RAM parity
interrupts in the middle or read or write operations. It would always be in
the same part of the BIOS in a loop waiting for the Interrupt Occurred flag
(bit 7) in the Drive Recalibration Status byte (40:003E) to be set. This
interrupt could always be safely ignorred and never affected the data
transferred or anything else that I ever noticed. I always used the PARCHK
utility to bypass it. I can't remember this problem being affected by the
CPU speed.
Do these problems suggest a problem with my controller?
Is the problem with the 360K drive due to a slow drive?
Is it something to do with it having come from a Tandy?
Could it have something to do with the resistor termination pack being in
or out? - I can't remember which it was and I didn't make a note of it
which suggests that I may not have been able to tell - the machine it
came out of was a single drive system as this is.
Another problem the system has is that the video card is very touchy about
being re-programmed (ie. in a switch to graphics mode) when the CPU is at
10 MHz. The screen will become a random pattern (looks like a flock of
seagulls) that slowly expands until I reboot the machine. This rarely
happened with Lotus 1-2-3 but almost always did with Autocad and many
other graphics programs. It almost never happens at 6 MHz.
Any clues on these problems from the hardware experts out there would
be most appreciated.
--
John Wright ////////////////// Phone: 902-424-3805 or 902-424-6527
Post: c/o Dr Pat Lane, Biology Dept, Dalhousie U, Halifax N.S., CANADA B3H-4H8
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