14 Oct
2012
14 Oct
'12
11:39 a.m.
On Oct 14, 2012, at 1:58 PM, Dave McGuire wrote:
On 10/14/2012 01:42 PM, js at cimmeri.com wrote:
There are a few obstacles. While none of them are "big" ones, they
all add up.
The biggest issue is that the people with enough time to do it seem to
usually not be the people with the required skillset.
Then there's a technical obstacle of bus driver chips that match Qbus
or Unibus specs. There just aren't any ideal choices that are available
now. There's an easy way around that, but then you're back to the
availability of time.
Those are exactly my issues. I've been wanting to make a QBUS
version of same for a long time now, and I certainly have the
skills, but my tuit supply is exhausted.
And the driver chips are a BIG problem. Probably the best
equivalents available now are the 74AS640 and 74AS760, but
they're really heavy hitters and would probably cause
unacceptable ringing on a really long bus. They'd most
likely be OK in a small QBUS enclosure, but I think a long
unibus system would be problematic. Anyone have any more
recent experience?
Nothing matches DEC's specs anymore, for probably obvious
reasons. The best I ever saw were some of the later NS
parts, which actually had an integrator on the output to
do slew-rate limiting. You could build something appropriate
out of discretes and op amps, but the amount of board space
you'd burn would murder you.
- Dave
>>> [...non-ancient disk on Unibus machines...]
>
> I'm surely not the only collector who would be willing to pony up
> some $$$ for such a project....
I would certainly pony up some $.
I built my own IDE->S-100 interface (with guidance from my amazing
friend, Allison P); it was very easy, hardware-wise.
What makes IDE to Qbus or Unibus interfacing so difficult? There must
be reasons, otherwise it would have been done by now.