PDP-8: (and others) anyone tried NVRAM simulation of hard drives?

From: David Gesswein <djg_at_drs-esg.com>
Date: Mon Feb 3 07:17:00 2003

>> From: Ethan Dicks <erd_6502_at_yahoo.com>
>
>That was one of my options. Any ideas about what to use for the
>cabling?
>
If you are keeping it short ribbon cable should work fine. If you were
running longer cables for multiple devices it might not be the best.

>What would you estimate the entire harness to run? $100?
>
I think you need 10 or 11 boards which the cheapest was about $7 so it could
be done for that. The cable connection will be tricky on the cheap extender
card. The grid card would be the best but most expensive.

>I was thinking of recycling the COMBOARD design - 1/4 of the memory
>map is "shared memory" - there is a circuit between the 68000 and
>the host bus that initiates DMA cycles when the 68000 reads/writes
>to it. I have used a COMBOARD to test the RAM in a PDP-11/03 via
>this shared memory interface.
>
Don't know if the 68000 has a fast enough clock to see the pulses or it
will need a little hardware assist. As long as you don't mind your peripheral
being brighter than the computer it should be viable.

From: Bob Shannon <bshannon_at_tiac.net>
>
>I beleive that Al got a few (one or two?) Augat wire-wrap quad DEC
>modules along with the CADR
>hardware. There was at least one quad unibus Chaos net interface board.
>But I have no idea of what an omnibus interface looks like electrically.
> Is this a painful thing to build?
>
Omnibus timing is a little strange but not that hard to work with.
It is similar to the 8/I external bus which is a daisy chained bus
with 10 or 11 cables for full version.
Received on Mon Feb 03 2003 - 07:17:00 GMT