On Wed, 4 Jun 2003, Ethan Dicks wrote:
> --- 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, that's no fun! I already have QBUS machines laying around I could do
that with (I don't think I have a working RLV12, however). I'm also
working on getting another machine with another RL controller to make this
work.
This is just something I'd like to be able to play with. A hardware
project to work on 'getting my hands dirty'.
> 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.
I tend to like either serial or ethernet for interfaces, because they're
fairly simple and nearly universal. This might be an interesting summer
project...
Pat
--
Purdue University ITAP/RCS
Information Technology at Purdue
Research Computing and Storage
http://www.itap.purdue.edu/rcs/
Received on Wed Jun 04 2003 - 17:12:00 BST