7 Aug
2008
7 Aug
'08
1:19 p.m.
On Wed, Aug 06, 2008 at 10:26:08PM -0700, Vincent Slyngstad wrote:
From: "Rich Alderson"
That sounds like a clever way to keep the costs per unit down.
I even have a few larger SRAMs (for a SBC6120 RAM disk board),
so if this project ever gets past the design phase, I'm past
the hump for the expensive components.
General question for PDP-8 fans: I've seen
references to someone having
created an RF08/RS08 replacement. Does anyone on the list know details
of such a project?
I have a project like that. You can find Eagle drawings at
http://www.so-much-stuff.com/pdp8/cadlib.html.
Look for "RF08: RF08 Replacement" in the green scrolling region.
The idea was to order an 8"x11" panel containing a controller, two
drive pairs, and a light panel. The "drive pairs" are implemented
with pairs of SRAM chips, which taken together form a removable
512Kw battery backed store. Two such stores provide the full 1Mw
of storage. Like many of my projects, it was fun to think about
the design,
but I haven't yet made the time to actually build and debug it.
One of these days, like when I'm home for more than six months at
a shot, I really want to shake down one of my Posibus boxes (i.e.,
watch it pass the entire suite of paper-tape diagnostics) and
hang some interesting hardware off of it.
Ever since I got that first PDP-8/L when I was in high-school, I've
been trying to get a OS/8-capable configuration. I've gotten as
far as an -8/L w/12kW (via a BM08) and PC8L high-speed papertape,
but no posibus mass storage. My negibus -8/i has 64kW of DF32,
but only 4kW of core (another long-term project is to get that up
to 8kW internally).
N.B.: The 74LS151's in the write-protect section
need to be real
TTL, and float their inputs high without pull-ups. Of course, if
you don't care about separate write-protect switches for each 32K,
you can just hard wire the inputs to the right values :-).
I don't remember seeing too many designs with floating TTL inputs.
Why no pullups? What's the advantage?
-ethan
--
Ethan Dicks, A-333-S Current South Pole Weather at 7-Aug-2008 at 20:10 Z
South Pole Station
PSC 468 Box 400 Temp -47.0 F (-43.9 C) Windchill -90.1 F (-67.8 C)
APO AP 96598 Wind 26.7 kts Grid 9 Barometer 681.3 mb (10579 ft)
Ethan.Dicks at usap.gov http://penguincentral.com/penguincentral.html