OT: how big would it be?

From: allisonp_at_world.std.com <(allisonp_at_world.std.com)>
Date: Wed Oct 20 13:21:09 1999

> My point is that using contemporary discretes I don't need a flip chip's
> worth of real estate to implement a read or sense amp. The problem posed
> was to build the thing using descretes, not discretes of 1960's vintage.
> Equivalent power density and beta is available in packages sometime two
> orders of magnitudes smaller -- although for core drivers the current
> density would force things to be physically larger...

Then you bring that out to interconnect technology and it grows though
moden connectors are smaller/denser than the DEC blocks.

> I can get a tremendous increase in density by using autorouted multilayer
> boards and SMD. If a 3' box fan positioned .5" from the board (quick, whose 70's
> data sheet is that a reference to?) doesn't keep it cool we can always immerse

 Signetics 82mumble WOM (write only memory) april first version.

> I wasn't considering cheating. Decoding is strictly combinatorial, so that's not
> tough. Driving and sense is much more of a bitch, and I probably can't get
> away with surface mount devices because of the current density requirements.
> Even so, I can build a similar function op amp using contemporary discretes in
> a hell of a lot less space than using 60's technology -- just the reduction in
> size of the passives gets me a hugh increase in density.

The key here is mid 60s technology means to me a simple decoder like a
3 to 8 is now a lot of parts small or not. Sit down and think out a
"equivelnt of the 74138 decoder as trasistors, diodes and resistors.
Bet you end up with a lot of them.

> I've lost context on the dissapation/cooling issue. Certainly we'd burn less
> and dissipate less (although more per square inch) than the original 8 did
> if we built an 8 using contemporary discretes, and a discrete implementation of
> an 8080 would run much hotter than the original 8.

Not much less. the disapation of the transistor was not size related but
the ability of a circuit to provide enough output for all the other loads.
Newer parts may have a higher beta, smaller size will have less
interconnect capacitance but we not in the order of magnitude department
here though it will be less. Newer devices would be smaller, faster,
and all but they are transistors and working at that level external
interconnect is very influential.

Allison
Received on Wed Oct 20 1999 - 13:21:09 BST

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