these RTL or what?

Tim Shoppa tshoppa at
Fri Oct 5 12:28:34 CDT 2007

Will wrote:
> Someone wrote:
>> VAX9000 built of ECL100K, fastest of the fast.  The second most common
>> use of TTL was in very high speed instrumentation and specifically frequency
>> counters and UHF PLLs.

> If the 9000 series was till using 100K, DEC must have been sleeping.
> By the 9000s development period, ECL was beyond 100K. I am not sure,
> but 10E may have been out by then. 10G maybe as well, but using that
> leads to insanity.

Using ultra-fast ECL doesn't make much sense when you've got nanoseconds
of delay to the backplane, to the next board, and back to the part that
needs the signal.

The ECL technology used in the VAX9000 was gate arrays with roughly the
same timing parameters as 100K ECL (0.5 to 1.0 ns propogation delays).

> But one thing I notice about DEC's ECL machines (9000, KL10) - for
> being ECL, there sure were ssssllloooowwwww.

KL10 was 100 series 10K ECL technology, typically 3 to 4 ns propgation
delay. A lot easier to build large systems with than say 74F00 stuff but
not a whole lot faster.

Responsiveness of a computer system depends on a lot more than the
speed of the semiconductors used to build it. Plenty of modern examples
of how to make fast silicon seem slow are coming out of Redmond I
notice :-).


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