20 Oct
1999
20 Oct
'99
6:39 a.m.
I have trouble with the notion of the uart filling a 9
x 11 board given
that I'm holding one that's occupying 4 x 5 inches in SSI. Yeah, the shift
registers would take a bunch of space but I don't see it using anywhere
near the amount of real estate suggested.
I'd suggest a electromechanical (or optomechanical) UART instead. You
know, like in a Teletype :-).
> A pdp-8 (early) had a pannel roughly
24"x50" with flip chip modules mostly
> transistors and the 4k core was a 10" tall rack section. for rough
> comparison. In many respects the 8080 is a far more complex CPU and would
> be significantly bigger. It would also be slow compared to the NMOS part.
I suspect you could build a pdp-8 using contemporary
layout tools and discrete
technology that, excluding the core stack, was an order of magnitude smaller.
And repackaging would also save a lot of money: a large part of the cost
of a Straight-8 is all those gold plated fingers and edge connectors, and
the backplane wiring. Get rid of that - so that your CPU resides on
a single (even if large) PC board - and you're way ahead. (Well, way
ahead if everyone else is still in 1965...)
> Doing it in ttl or bit slices would still be big,
I've done that. using
> 2900 parts(ca mid to late '70s) the CPU equivelent was over 100 chips and
> filled 4 10x8" cards.
That sounds about right; I recall building a PDP-11
clone using 2901/2910 parts
as part of an undergraduate CPU architecture course in the same era and using
about the same number of parts.
Of course it's also possible to do it on a single card using SSI and
MSI TTL, maybe with a few bipolar PROM's. Take a look at the 11/04 CPU or
the original Nova, for example.
I recall - back in the mid-70's - that Radio Shack sold transistor-based
logic module kits (PC boards) that could be strung together to make
things like binary counters, etc. Does anyone else here remember these?
Or, even better, still have the modules around?
--
Tim Shoppa Email: shoppa(a)trailing-edge.com
Trailing Edge Technology WWW: http://www.trailing-edge.com/
7328 Bradley Blvd Voice: 301-767-5917
Bethesda, MD, USA 20817 Fax: 301-767-5927
20 Oct
20 Oct
7:03 a.m.
>> Doing it in ttl or bit slices would still be
big, I've done that. using
>> 2900 parts(ca mid to late '70s) the CPU equivelent was over 100 chips and
>> filled 4 10x8" cards.
Note: I did this using HIGH desnity augat pannel boards (those ones with
rows of WW pins spaced alternate .200, .300 so they could take .300 dips,
.600 dips, and SIPs (resistors).
The goal was to build a 8080 that ran most of the z80 instruction set
without the EX and EXX (one set of registers) faster than a z80. The z80
by 1984 was faster than the result (more piplining, faster 2901Cs pray to
the goddess of uCode). It only wanted 1,000-3,000% more power than a
z80H.
Allison
7:09 a.m.
New subject: 'Inter-library' loaning
Hi Gang,
Probably like most of you all, I've got a large number of systems that I
unfortunately cant play with at the same time. I don't really want to part
with any of my toys but I also don't think I'd have a problem temporarily
loaning things in exchange for a chance to play other equipment for awhile.
Any thoughts on how this might be accomplished securely?
Regards
- Mike: dogas(a)leading.net
8:26 a.m.
New subject: Designs (was Re: OT: how big would it be?)
Ok, so who would be interested in creating a repository of "generic" gate
designs?
Are the flip chip cards copyrighted? (Somehow I doubt Compaq would come
after us if we started building them :-)
Are they the correct technology? I like 'em because you can get to parts of
the circuit easily, but it is more compact to put everything on just a few
boards.
Have we ruled out using SMT technology? We could easily build a 16 bit
register on a single flip chip sized card with SMT stuff.
--Chuck
9:28 a.m.
New subject: Designs (was Re: OT: how big would it be?)
Are they the correct technology? I like 'em
because you can get to parts of
the circuit easily, but it is more compact to put everything on just a few
boards.
Flip chips, M series and all were really dictated not by what could be put
on a board but how many connections the bord could make. For a flip chip
it was 18 or 36 (someone?). A 16 bit parallel load register like say a
pair of LS573s would need 32 IO, plus power and controls. See the
problem?
Even TTL chips hit the wall in pins/functions per package.
Allison
10:12 a.m.
New subject: Designs (was Re: OT: how big would it be?)
At 02:28 PM 10/20/99 -0400, Allison wrote:
Flip chips, M series and all were really dictated not
by what could be put
on a board but how many connections the bord could make. For a flip chip
it was 18 or 36 (someone?). A 16 bit parallel load register like say a
pair of LS573s would need 32 IO, plus power and controls. See the
problem?
Ok, so this suggests a possible solution/idea. We use simm sockets. You can
get them fairly cheaply, there is a wirewrap version, and the PC houses all
have a standard template for the bottom of the board. I suppose one could
even make a Q-bus that small (its 72 pins as well IIRC).
Unlike Tim I think TO-3's would be way to much of a pain, but TO-92s are fine.
--Chuck
12:13 p.m.
New subject: Designs (was Re: OT: how big would it be?)
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ard＠p850ug1.demon.co.uk -
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