--- Tony Duell <ard_at_p850ug1.demon.co.uk> wrote:
> An alternative approach (and one that I'd probably try) would be to use a
> real RL11 (or similar), a Unibus (or as applicable) RAM card, and a
> home-made bus master/arbiter that could tall the RL11 to read a sector
> (using DMA into the RAM card) and could then read out the RAM to the host
> computer. Doing something like that would let your PC (or whatever) talk
> to just about any small DEC disk drive using the appropriate Unibus
> controller.
If you are going to do that, why not use a DEC CPU?
It's a nice idea and all, but at that point, wouldn't a real PDP-11
be easier to talk to (and not much more expensive than a box with
a controller and some RAM)?
Why not just use a PDP-11/53 CPU board with local serial and on-board
RAM? The trick then would be to whip up some kind of protocol between
the PeeCee and the PDP-11 to manipulate the disk registers and fetch
blocks on command. If you wanted something to transfer blocks faster,
there are DRV11s that could blow the data out in parallel fashion.
There's also the possibility of porting code from the 2BSD distribution
to run out of a RAM disk... then you could even use existing drivers
and talk to the PeeCee at a high level instead of proxy register tweaking.
Except for the local RAM requirement for disk buffers, I could probably
whip something together with a COMBOARD. Unfortunately for me, the model
I'm most abundant in has COM5025 serial chip - the scarce models are
later ones with a Zilog Z8530.
If someone wants to design a microcontroller-based Qbus/Unibus register
thumper from scratch, I'd consider building one. Best to define how
to talk to it from the outside before getting too far along on the design.
-ethan
Received on Wed Jun 04 2003 - 13:40:01 BST