[rescue] Cheapass MicroFax (sic)
mcguire at neurotica.com
Fri Jan 24 15:55:07 CST 2003
On Friday, January 24, 2003, at 04:41 PM, Bill Martin wrote:
>> ...or you can just post here. There are lots of DECheads here.
>> The pdp11 field guide covers many boards which can be used in both
>> PDP11 and VAX systems.
> Both? Are they 16 bit, or do they somehow autodetect?
Qbus is a 16-bit data bus with either a 16-, 18-, or 22-bit address
Only some machines actually put the memory on Qbus...most of the Qbus
PDP-11s do, except for the 11/83, /84, /93, and /94. The only Qbus VAX
that goes through Qbus for memory access is the MicroVAX-I. The other
machines use a PMI (Private Memory Interconnect) of one sort or
another. See that ribbon cable connecting the KA640 to its memory
board(s)? That's the PMI.
> Wasn't the Vax a clean sheet architecture hardware-wise? (I have a
> lot to learn. Great fun!)
Processor architecture != bus interface. The first VAX, the 11/780,
used Unibus as its I/O bus. Later VAXen used Qbus, BI, XMI, and
> And I thought Sun SPARC boxes were well built. I'm impressed, though
> I was already impressed by the PWS433au I bought a couple of months
Ahh, even the PWS machines are *nothing* compared to this. Right
down to the thickness of the metal in the chassis.
> Can you tell by now that I'm an engineer? Retired now, got into
> management in later years, but once an engineer... (Yes, I confess my
> sellout, a suit. But it is/was mechanical engineering, so I had
> nothing professionally to do with computers except as a user and when
> experiencing jealousy (imagining the MIS (remember MIS?) guys' fun)
> and frustration (when they wouldn't let me do what I wanted. Like buy
> a CP/M box. Though they did give me the first PC in the company
> (Southern Railway.)) So please, no flames.)
We forgive you. This time. ;)
Dave McGuire "Wear whatever you want...Just don't be surprised
St. Petersburg, FL if you wind up with a blow-gun dart in your
prosthetic boobies." -Kurt Huhn
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