A TALE OF WOE AND/OR INTRIGUE ABOUT DISK CONTROLLERS

[Lindsay Cleveland]

[ Posted for someone with no netnews access...]
  From:  Neal Rhodes (gatech!stiatl!clkwrka!neal)


We have an AT&T 6386E.  Which is to say a 20mhz 386 with an ESDI controller
driving a 135mb Micropolis drive.  It has a Dos partition but is mostly used
for Xenix.

We have from a prior now defunct machine a ST506 drive; in fact a Seagate
4096 80mb drive.  We thought, "wouldn't it be neat to put this in the 6386".
Being not quite as dumb as we look, we called Western Digital, and they 
suggested we buy a WD1004a-WX1; an 8bit ST506 controller.  This, they say, 
should not conflict with the 16bit WD1005-WAH ESDI controller.  And SCO said
they would be happy dealing with a second controller.

To cut to the chase, we have gotten this done to where it kinda-sorta wants 
to work.  The Wx1 is set to be a second controller at CA00:0 using IRQ5;
the 4096 is formatted and such.  The problems are as follows:

1. During powerup diagnostics, the system doesn't appear to do anything for 
about 14 seconds after the 
	Option Rom at CA00:0000		Pass
message and before the
	Option Rom at DE00:0000		Pass
message. (front panel controller I believe)  I could live with the delay, but
I think it is a symptom of something worse.

2. It will boot PC-Dos from a floppy diskette, and both drives can be accessed
apparently OK.

3. If we try to boot Dos from the ESDI drive, it will hang at some point after 
the printer is initialized.  The disk light appears to stay on.

4. If we try to boot Xenix from the ESDI drive, we get:
	Boot0: error 04


WD has been real sympathetic; they suggested we move the 506 controller to 
show up at CC00:0000.  We tried that and discovered that it cleared up problems
1, 3, and 4.  You just can't access the second drive at all from Dos or Xenix
even though the Rom message shows up.   They were also suspicious about a 
controller built for a 4.7mhz XT being used in a 20mhz cpu.  

AT&T has been somewhat informative, but they say they use their own rom for 
the disk controller and do not support anyone else's hardware.  They do claim
that their 8 bit slots are run at 4.7mhz.

Sooooo, we are looking for clues, suggestions, anyone who has done this, has
proven it can't work, or who wants a ST4096 complete with controller.  


Thanks,

Neal Rhodes

gatech!stiatl!clkwrka!neal