20 Oct
1999
20 Oct
'99
5:19 a.m.
> According to the intel Web site an 8080 has about
6000 Transistors.
> Now, it is possible to put up some 12 to 16 FF gates in discrete
> logic (discrete non SMD transistors etc.) gates (~40 Transistors)
> onto one Euro-Card board (I tid once build up 16 FFs on one board
> - at the age of 16, I tried to miniaturize :). So, spreading 6000
> transistors at 40 transistors per board gives some 150 boards.
> And with an asumption of 20 boards per row we need some 8 rows,
> or a small (half height) rack.
With gating and interconnect it will grow.! Also that
would be a CPU chip
replacement... memory, IO and control pannel would be needed.
Well, the whole question was about a CPU chip replacement,
_not_ a working computer including maybe 64K of Mem.
I think the key is yes it can be done. Yes with moden
discretes and
technology you can compress it. However the devil is heat and a SMD
transisor at 10mW per is going to get hot with 40 per board! Why 10mW?
You have to drive wires and other gates and these are not MOS devices like
on the chip (you can but you still used real resistors) so things like
fanout/fanin are considerations.
Well, I assumed _non_SMD - 10 mW per transistor isn't a wrong
asumption - also you should add some 50% more heat dispendes
by the needed resistors. So .6W per board sounds right - but
thats stil no big hassle. Using a proper rack, even 10W per
card can be handled without problems (with good airflow of
course).
While there are small serial computers a look at them
shows some things
that need to be reflected upon. They were serial archetectures and
minimized the used of things like registers as they were hardware
intensive. The Minuteman Missle computer I"d played with many eons ago
was such an example. Flipflops were very scarce in that machine.
Jep, but using a way different architecture than the original
CPU would again miss the design goal (at least in my opinion).
In fact, I've meditated over a similar question several times:
Wouldn't it be great to have 3 C64 at display (in a museum) with
3 different incarnations of a 6502(6510) - one with the 'real'
chip, one with a TTL replacement on lets say one board (like
Dicks wire wrap) and the third utilizeing a big box with transistors.
(And before y'all argue about backdraws, of course I know that
it is close to imposssible to get the TTL running at 1 MHz inside
the NMOS specs, but that can be solved by lowering the CPU clock
and selecting an aprobiate Application :)
I just belive this would give a _great_ display - unlike all
these dump displays where they put a sack of transistors beside
a uP and tell you just that they are equivalent.
Anyway
Gruss
H.
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Ich denke, also bin ich, also gut
HRK