OT: how big would it be?

From: Chris Kennedy <chris_at_mainecoon.com>
Date: Wed Oct 20 13:44:16 1999

allisonp_at_world.std.com wrote:
>
> > 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.

Yep. Suddenly this is starting to sound like something out of The Journal
or Irreproducable Results...
>
> > 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.

Oh, she's good. She's very good.

>
> > 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.

You're right, and I did. The number of components turns out to be fairly
ugly, although they can still be made to fit in a fairly small area --
although we'd need robotic assembly to place all the stuff -- and that's
assuming I didn't grossly screw up this design. Maybe I should spice it... ;-)

> > 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.

Absolutly no argument here. We play the same game in processor design
today; drive requirements (both due to fan out and L/C) make the
drivers bigger -- which drives up space, power and disapation requirements.

Mind games like this are fun at times; they remind us that, at least at times,
the more things change, the more they remain the same.

Best,
Chris

-- 
Chris Kennedy
chris_at_mainecoon.com
http://www.mainecoon.com
PGP fingerprint: 4E99 10B6 7253 B048 6685  6CBC 55E1 20A3 108D AB97
Received on Wed Oct 20 1999 - 13:44:16 BST

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