7 Apr
2007
7 Apr
'07
8:55 p.m.
The Option Board was, IIRC, completely software-driven
and extremely
susceptible to machine speed (and sometimes even interrupt noise, which
is why they made TCS.EXE which doesn't use EMS and might disable some
hardware interrupts as well). The fastest machine I could get it to
work in reliably was an AMD 386-40, with the ISA bus speed at either
clock/5 (8MHz) or locked at a timer clock integral divider (ie.
7.16MHz). If memory serves, I had the best results at 7.16MHz.
Currently I keep mine in my 5160.
I have the bus set to 7.16 Mhz, all the wait states I can get turned on,
cache turned off etc - but I think the 486 is still too fast for it.
Slower. Look for ICD.COM (and companion ICE.COM)
which disable the
internal cache. I believe you can find a copy of them here:
http://www.oldskool.org/guides/oldonnew/resources/icdice.zip
Also, add wait states if possible. Fix bus speed at or close to ISA
standard (see above).
Sad thing is I don't have any 386s or AT any more (Actually I have a
Compaq portable III, but that a bit tough to screw around with - I
might try it in a 5160 - that should be slow enough :-)
I heard through the grapevine that, sadly, the creator
of the Option
Board (everything, hardware to software) passed away in the mid 1990s,
so there is no official resource to ask about the OB. But it was always
one of my favorite peripherals, and just watching it try to match track
length while copying gave me some insight into FDC operation (and
protection methods!)
In my case, the board would take FOREVER to match the track length - another
clue that it's having timing problems - Often several minites/track - I had
to open it up to get it to work at a reasonable speed. As noted previously,
I was just trying to copy a generic 360K dos disk. Just trying to see if the
board workd.
I used to have programming information on the OB; I
don't know where it
is but I can try to dig it up if you think you'd find it useful. Also,
I'm assuming you've seen the treasure trove of info over at
http://retro.icequake.net/dob/ ?
Yes I did thanks - I believe thats where I got the newer software version.
Is there any detailed information available on the DOB (I understand the
OB and the DOB are different)?
Dave
--
dave06a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools: www.dunfield.com
com Collector of vintage computing equipment:
http://www.classiccmp.org/dunfield/index.html