bit slice chips (was Re: Harris H800 Computer)

Brent Hilpert hilpert at
Sat Apr 23 16:34:36 CDT 2016

On 2016-Apr-23, at 10:06 AM, Chuck Guzis wrote:

> On 04/23/2016 05:41 AM, Noel Chiappa wrote:
>>> From: Brent Hilpert
>>> I'd say the 74181 (1970) deserves a mention here. Simpler (no
>>> register component, ALU only) but it pretty much kicked off the
>>> start of IC-level bit slicing.
> I recall reading about the 74181 introduction back in the day--it
> created great excitement and speculation about how far the industry was
> from a computer-on-a-chip.  I think I still have a couple of the things
> in my hellbox.

In 1972 or 1973 one of Radio Electronics or Popular Electronics had a construction article for the E&L Instruments Digi-Designer.
If you recall, the Digi-Designer was essentially a vehicle for E&L's new plug-in breadboard.  For those younger, yes, -those- plug-in breadboards, that are still the most prevalent hardware prototyping/educational technique today.

AIR, the 74181 was featured as an experiment to wire up on the Digi-Designer in that article.

> In the day, I'm not certain that TTL had the edge on integration,
> however.  It always seemed that DTL and RTL had the edge in complexity.
> Before the 181, I was playing around with the RTL 796 dual full adder
> and an 8-bit Fairchild DTL memory--IIRC the latter used a 7V clock.

I think TTL was quickly on par for density with DTL & RTL and overtook them by the late 60s.

I have 7490s (decade counter) from late-1966 and early-1967, and many TTL MSI functions were there by 1969.
The 7484 (16-bit memory) is listed in the TI 1969 TTL databook.
RTL was passe by then and DTL was heading that way. I don't think DTL got any more complex than such as the 8-bit memory you mention, at least in the main.

I was surprised by the early date code on the 7490s when I ran across them in a piece of test equipment.

> The interesting thing was that there seemed to be a distrust of LSI
> chips early on.  I recall working on a project around 1973, where the
> lead engineer preferred to design his own UART from SSI rather than use
> one of the new UART chips.
> --Chuck

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