20 Jan
2004
20 Jan
'04
8:29 a.m.
Ethan Dicks <dickset(a)amanda.spole.gov> wrote:
Yes, but some devices are not so old and _do_ use
ASICs. There are some
peripherals that came out at the same time as the 11/20 (~1970) that
they are made up of several square feet of TTL/Linear chips.
Well, what I meant was that UNIBUS and Q-bus were designed to be implementable
without ASICS using only discrete logic, and the simpler devices were
implemented that way.
Unibus? 8640, 8641, 340, 8881, DC013 (custom DEC
chip)
Qbus? DC003, DC004, DC005, DC006, DC010, 74LS240, 8837, 8838
In other words, with few exceptions, *not* ordinary TTL chips (though ISTR
one of their busses used hand-selected 7438s chosen for low (1uA?) leakage.
Hmm, 74LS240 for Q-bus? It's just a standard three-state TTL inverting buffer,
isn't it? For driver, receiver, or both?
designed-as-such bus drivers/receivers from companies
like
National Semiconductor.
Does NS still make them?
MS
20 Jan
20 Jan
8:37 a.m.
On Tuesday 20 Jan 2004 7:29 pm, Michael Sokolov wrote:
Ethan Dicks <dickset(a)amanda.spole.gov> wrote:
Not since I last checked.
alex/melt
Yes, but some devices are not so old and _do_ use
ASICs. There are
some peripherals that came out at the same time as the 11/20 (~1970)
that they are made up of several square feet of TTL/Linear chips.
Well, what I meant was that UNIBUS and Q-bus were designed to be
implementable without ASICS using only discrete logic, and the simpler
devices were implemented that way.
Unibus? 8640, 8641, 340, 8881, DC013 (custom DEC
chip)
Qbus? DC003, DC004, DC005, DC006, DC010, 74LS240, 8837, 8838
In other words, with few exceptions, *not* ordinary TTL chips (though
ISTR one of their busses used hand-selected 7438s chosen for low
(1uA?) leakage.
Hmm, 74LS240 for Q-bus? It's just a standard three-state TTL inverting
buffer, isn't it? For driver, receiver, or both?
designed-as-such bus drivers/receivers from
companies like
National Semiconductor.
Does NS still make them? 
8:43 a.m.
On Tue, Jan 20, 2004 at 11:29:42AM -0800, Michael Sokolov wrote:
Hmm, 74LS240 for Q-bus? It's just a standard
three-state TTL inverting buffer,
isn't it? For driver, receiver, or both?
I don't recall, but I've seen it on 3rd-party boards where DEC would use
a DC005. Without schematics, I can't guess.
-ethan
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