20 Oct
1999
20 Oct
'99
6:21 a.m.
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