On Thu, May 13, 2004 at 10:34:22PM +0100, Tony Duell wrote:
> > The real question is: What is more time consuming? Rebuild the RK07 or
> > build a solid state RK07 replacement.
>
> It also depends on what you want to do. To me, a classic computer system
> is more than just the CPU. The peripherals are part of it as well.
> Running a PDP11 with flash memory mass storage is not the same as running
> one with a demountable hard disk.
While in principal I agree, in years gone by, I was unable to do more than
play-load 2BSD on a real 11/24 because my largest Unibus disk (that wasn't
on a UDA-50) was and still is RL02s on an RL11. These days, I have bigger
Unibus CPUs (11/44, 11/70), but in terms of pre-MSCP disks, 10MB is still
a limit for me (fortunately, I can get around this with 2.11BSD on the 11/44
or the 11/70, but 2.9BSD was it for non Split I&D machines)
Even though I appreciate and admire the older disks, I'm pretty much stuck
with RK05 and RL01/2. I'd love a solution that emulates _some_ DEC disk
controller (to avoid burning boot PROMs, writing drivers for every OS I'd
want to play with, etc.). In order, a good solution for me would work
with 2BSD, RT-11, RSX and RSTS... there's plenty of interfaces that fit
the bill. If I weren't worried about compatibility, I'd probably just
go down to the basement and hack something into a Unibus COMBOARD (68000-
based communication controller w/DMA interface, 16K/32K EPROM, 128K RAM,
5025 sync UART, 6821 PIA...) I've thought about those stick-in-the-socket
interfaces for slotless Amigas - both IDE and SCSI are available. The
one thing that stinks is that for a disk controller, a sync UART is pretty
much useless... I'd consider swapping that out for some other chip. We
used Z8530s on our Qbus and VAXBI designs.
> DEC managed with a handful of TTL. You don't _need_ an FPGA. You'd want
> to do DMA, which means that your device has to source the bus address,
> but that's not hard (a counter + buffers, basically). You also need the
> word count register (another counter), and some glue logic. Not that hard
> to build.
It's pretty well documented in the DEC "Bus Handbook" - I have it on paper
at home, and I'm pretty sure it's on bitsavers - I know I've seen it online
somewhere.
We just went with the DEC bus chips, not an option these days, though, unless
like me, you happen to have a pile of 8641s and DC013s...
-ethan
--
Ethan Dicks, A-130-S Current South Pole Weather at 13-May-2004 22:20 Z
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Ethan.Dicks_at_amanda.spole.gov http://penguincentral.com/penguincentral.html
Received on Thu May 13 2004 - 17:37:18 BST