7 Aug
2008
7 Aug
'08
3:29 p.m.
From: "Ethan Dicks"
The RX8 will go in the middle of a bus, and even has a provision for a
G717 equivalent bus terminator, in the form of an optional SIL resistor
pack. Real drivers, too. Of course, being known not to work as yet,
I doubt anyone will be rushing out to build it :-(.
Vince
On Thu, Aug 07, 2008 at 02:27:19PM -0700, Vincent
Slyngstad wrote:
It is a little. The 8"x11" restriction is really just to keep the
prototype cost low for a particular board shop. If that or the
10mil restriction were relaxed, things would get easier.
Of course it would also be fairly easy to redo the thing with
GALs instead of TTL, which should also make it easier to fit
things in, but would require me to program parts.
No particular reason, but the board's pretty
crowded trying to get
it all to fit in 8"x11". I'd probably use SIL resistor packs and
shift down the six DIPs below the switches. (I'm not sure there'd
be enough void left to route the thing with 10mil design rules.)
Sounds crowded. There's
some other "fast and loose" stuff in there too -- S240 as
bus drivers, multiple LS loads on the bus (still should be less
than a 74xx load), and (importantly) no provision to continue the
bus, so that it must be placed last. There's also no equivalent
for the G717 terminator card, so it may need to be a fairly short
bus!
Well... while that's not optimal, it's workable. Given the dearth
of OEM posibus equipment these days (I have none and have never
seen any except on the web), it's not like many people are going to
be sticking this on a heavily loaded bus. The RF08 is large enough
to do interesting things with, leaving only removable media to get
things on and off the system - paper tape is certainly one way,
but floppies are more convenient... in my particular case, I suppose
the largest configuration I'd attempt would be a modern solid-state
RF08 and that RX8 you/we started and haven't gotten back to. It's
been so long that I can't remember if the RX8 can be in the middle
of the posibus or not.