According to Waldek Hebisch <
antispam@fricas.org>:
John Levine <johnl@taugh.com> wrote:
It's also seems rather high for the /91. I can't find any authoritative
numbers but 100K seems more likely. It was SLT, individual transistors
mounted a few to a package. The /91 was big but it wasn't *that* big.
I remember this number, but do not remember where I found it. So
it may be wrong.
However, one can estimate possible density in a different way: package >probably of similar dimensions as VAX package can hold about 100 TTL
chips. I do not have detailed data about chip usage and transistor
couns for each chip. Simple NAND gate is 4 transitors, but input
transitor has two emiters and really works like two transistors
so it is probably better to count it as 2 transitors, and conseqently >consisder 2 input NAND gate as having 5 transitors. So 74S00 gives
20 transistors. D-flop probably is about 20-30 transitors, so
74S74 is probably around 40-60. Quad D-flop bring us close to 100.
I suspect that in VAX time octal D-flops were available. There
were 4 bit ALU slices. Also multiplexers need nontrivial number
of transistors. So I think that 50 transistors is reasonable (maybe
low) estimate of average density. Assuming 50 transitors per chip
that would be 5000 transistors per package. Packages were rather
flat, so when mounted vertically one probably could allocate 1 cm
of horizotal space for each. That would allow 30 packages at
single level. With 7 levels we get 210 packages, enough for
1 mln transistors.
I don't see what this could have to do with the 360/91. As I said,
it was built with SLT, a few individual transistors and resistors
per package.
IBM's first integrated circuits were MST used in the 360/85 and System/3.
Pugh et al are kind of vague about how many transistors per chip but they
show an exemplar circuit with six transistors and say there were up to four
per chip so that's still only two dozen transistors per chip.
I realize that densities got a lot greater, but that was S/370 and beyond.
--
Regards,
John Levine,
johnl@taugh.com, Primary Perpetrator of "The Internet for Dummies",
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https://jl.ly
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