brew-your-own-unibus boards?

From: Ethan Dicks <>
Date: Tue Jan 20 12:39:20 2004

On Tue, Jan 20, 2004 at 10:03:06AM -0800, Michael Sokolov wrote:
> Here's my take on the issue of not being able to use standard drivers and
> receivers for UNIBUS and Q-bus. Aren't both of these buses old enough that DEC
> made devices for both of them using only discrete logic, no ASICs?

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.

> If they did make UNIBUS and Q-bus devices w/o ASICs using only standard
> discrete logic, as I'm sure they did, what did they use for drivers and
> receivers?

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.

There are _some_ bus lines that can be loaded/driven by ordinary parts.
However, unlike an ISA card, DEC cards tended towards custom chips of
their own, or designed-as-such bus drivers/receivers from companies like
National Semiconductor.

These are from memory, so if I've made any mistakes, I'm sure someone will
correct me. :-)


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Received on Tue Jan 20 2004 - 12:39:20 GMT

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