William Donzelli wdonzelli at
Wed Jan 31 22:07:47 CST 2018

> And, if you went to 74S, Fast or 74AS, you could easily match the ECL
> 10K performance.  Now, there were a bunch of tricks that you could use with
> ECL that helped, like wired-OR instead of adding a tri-state buffer.  ECL
> had a notable advantage in 1970, but as TTL derivatives continued to
> advance, that shrank to nothing.

If you are comparing 74S/AS/F TTL to 10K ECL, you are making a unfair
comparison. When the 74S and 10K were introduced in the very early
1970s, 10K ECL was not the fastest ECL available, MECL III was. MECL
III was almost three times faster than 10K, but was expensive and
difficult to use. It remained in front line use until the mid-1970s,
simply because nothing could touch it. 10K became the popular ECL
family because it was the easiest to use and would not break the bank.

Additionally, when 74AS was introduced, 100K had already been
established, with 10KH following shortly thereafter. 100K was very
easy to deal with, as long as ALL the rules in the databooks were
followed, but like MECL III, very expensive (a normal glue logic chip,
like a 100101 triple OR/NOR was seven bucks in DIP, compared to thirty
cents for something similar in TTL). Later still, 10E/100E was even
faster, down to typical 400 pS gate delays - still something that TTL
could not touch at the time. To top in off, 10G was a little faster
that 10E/100E.

Also, running 74S at full throttle often results in a real shitshow on
the circuit board. It is far easier to run ECL at full speed

CMOS killed ECL, not TTL.


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