Cray-I basic gates

[Thomas Koenig]

[xpost to comp.arch and ald.folklore.computers, f-up to
comp.arch]

Reading literature on the Cray-I, one finds that their logic was
implemented in ECL using 5/4 NAND gates.

Wikipedia claims that these were, in fact, XOR gates, but the only
source to that claim is a link to a datasheet, without a source
stating that this chip was indeed used in the Cray-1, so I am
disinclined to believe that (and I may just remove it as being
unsourced, and in contradiction to published literature).

The pictures of circuit boards that I found that were big enough
to read the markings only had the flip-flops and the static ROMs
on them.

So, does anybody have an idea of what they actually used (and
maybe a source)?

[Brian G. Lucas]

Post by Thomas Koenig
[xpost to comp.arch and ald.folklore.computers, f-up to
comp.arch]
Reading literature on the Cray-I, one finds that their logic was
implemented in ECL using 5/4 NAND gates.
Wikipedia claims that these were, in fact, XOR gates, but the only
source to that claim is a link to a datasheet, without a source
stating that this chip was indeed used in the Cray-1, so I am
disinclined to believe that (and I may just remove it as being
unsourced, and in contradiction to published literature).
The pictures of circuit boards that I found that were big enough
to read the markings only had the flip-flops and the static ROMs
on them.
So, does anybody have an idea of what they actually used (and
maybe a source)?

I'm pretty sure that the NAND gates and Flip-Flops were
Motorola ECL. I remember Motorolans from Austin talking
about how they hated going to Chippewa Falls in the winter.

[MitchAlsup1]

Post by Thomas Koenig
[xpost to comp.arch and ald.folklore.computers, f-up to
comp.arch]
Reading literature on the Cray-I, one finds that their logic was
implemented in ECL using 5/4 NAND gates.

CRAY-1 was built with (IIRC) dual 4 input OR/NOR gates MECL-III 1660
The flip-flop chips MECL-III 1666, the random access memory cell
MECL-III 1680, and the quad line receiver MECL-III 1692. If an XOR
gate was used, it was only in the FP multiplier. These are from my
1969 MECL data book. One interesting factoid:: the 1975 MECL book
has 11 pages of how the flip-flop was tested, whereas the 19769
book only has 2 pages of how this chip was tested. My guess is
CRAY found a testing anomaly in the Motorola Factory on this part.

More interestingly, Cray-1 had 4 lengths of wire--1 foot, 2-foot,
3-foot and 6-foot of RU58 coax. corresponding to roughly 2ns delay,
4ns delay, 6ns delay, and 1 clock of wire delay.

ECL gates are inherently NOR logic and come with True and Complement
outputs. {{NOR assumes you think -0.8V is high and -2.0V is low--if
you think -0.8 is low than they are NAND gates.}}

An ECL NOR gate is a differential amplifier with an emitter follower
output gate.

An ECL NAND gate is a stack of differential amplifiers with emitter
follower level shifters for the lower differential amplifiers and
emitter follower output gates. These NAND gates are slower (20%-30%)
than NOR gates, so logic designers learn how to use the inverted outputs
of the NOR gates, except in certain circumstances. ECL NAND gates are
often used as linear modulators.....

Post by Thomas Koenig
Wikipedia claims that these were, in fact, XOR gates, but the only
source to that claim is a link to a datasheet, without a source
stating that this chip was indeed used in the Cray-1, so I am
disinclined to believe that (and I may just remove it as being
unsourced, and in contradiction to published literature).

This is incorrect. An ECL XOR gate is much like a NAND gate and even
slower. The Gallium Arsenide machine Seymour was working on after
leaving CRAY had this XOR characteristic.

Post by Thomas Koenig
The pictures of circuit boards that I found that were big enough
to read the markings only had the flip-flops and the static ROMs
on them.
So, does anybody have an idea of what they actually used (and
maybe a source)?

See above:: to anyone in the Austin Tx. area:: I have these books
and you can come an read them if you like. I may have some old
CRAY literature, too.

[John Levine]

Post by Thomas Koenig
So, does anybody have an idea of what they actually used (and
maybe a source)?

Bitsavers has some manuals like this one:

https://bitsavers.org/pdf/cray/CRAY-1/2240004C_CRAY-1_Hardware_Reference_Nov77.pdf

Section 2 describes the various chip types.

[quadibloc]

This post finally reappeared on my PAN newsreader with Eternal September...

and, although I couldn't find it initially in the category-based interface,
the newsgroup comp.arch is also available through NovaBBS also known as
Rocksolid Light.

John Savard