31 Jan
2003
31 Jan
'03
10:58 a.m.
--- David Gesswein <djg(a)drs-esg.com> wrote:
From: Ethan Dicks <erd_6502(a)yahoo.com>
That was one of my options. Any ideas about what to use for the
cabling? I've seen three types used in real DEC hardware - coax
(with the lowest propagation delay and longest bus lengths possible),
mylar flat cable, and stranded-wire ribbon cable. Obviously, a roll
of ordinary ribbon cable is probably going to be the cheapest and
easiest for hobbyists to work with. I suppose with only one device,
and in the same cabinet, it shouldn't pose too many problems.
What would you estimate the entire harness to run? $100?
One thing that has been slowing me down is
deciding how to attach a modern device to an -8/L or -8/i...
I would recommend getting the DEC compatable cards for Dougless
Electronics to plug into the 8/I and wiring them to another circuit card. With a bank of transistors you can convert from the
negative bus to TTL
and put a small FPGA/CPLD on the board to do all the work.
If I were more comfortable with FPGA/CPLD design, I would probably go
that route. My expertise is more in microprocessors; I was contemplating
throwing an MC68000 on the other end of the bus since I have extensive
stocks (dozens of tubes), a large assortment of hardware debugging tools
(code trace analyzers, a Flike 9010A, etc.) and lots of expertise.
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.
Not the most efficient way to do it, but with the tools/skills I have,
it's how _I_ would do it. Naturally, if someone else does the engineering
work, I can *build* stuff that I didn't design.
-ethan