VAX9000 unearthed

[Jon Elson]

On 2/20/22 14:31, Chuck Guzis via cctalk wrote:
> On 2/20/22 10:10, Mark Kahrs via cctalk wrote:
>> I heard Butler Lampson once exclaim that ECL design was in some ways easier
>> than TTL.  If you terminated every line, you get controlled impedances with
>> controlled edges.  This was the design philosophy for the Dorado.
Yes, quite true.  Really short lines could be left 
unterminated, but you still needed a pull-down resistor.
> Indeed--ECL WW prototype boards usually had a 3rd row for SIP
> termination resistors alongside the DIP sockets.  One nice thing about
> ECL is that there are many fewer problems with power rail spikes.  On
> the other hand, the constant power consumption needs beefier power supplies.
>
> I recall that Honeywell redid one of their mainframe designs in ECL,
> with somewhat disappointing performance results.  I don't recall the
> details offhand.
>
Yup, I was trying to speed up a baud rate divider that was 
already using AS or FAST 4-bit counters.  I worked out how 
much faster I could do it with ECL, and the result was not 
worth it. But, back in the days when TTL was king, before 
LS, AS and FAST, ECL had a REAL advantage.

Jon