20 Oct
1999
20 Oct
'99
8:09 a.m.
Yes, I agree that you'd want to approach things differently than you do your
work. Perhaps an attempt at wire-wrapping a processor with "period"
components? I mentioned that I did that once. It wasn't until I tried that
that I came to appreciate how thrifty the processor really is when compared
with others.
Of course, you may not find that to be fun either.
Building an S-100-based 8080 core out of TTL offers an added benefit in that
the 8080 timing logic suits the S-100 bus signal layout and timing. When
you're done, there's a wealth of software you can play with. I would say
you ought to be able to build a processor core twice as fast as the original
8080A, jet using only a single supply.
It's not likely I'll do that, but it is a tempting notion.
Dick
-----Original Message-----
From: daniel <daniel(a)internet.look.ca>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Wednesday, October 20, 1999 11:06 AM
Subject: Re: OT: how big would it be?
and
G-15.
-----Original Message-----
From: Richard Erlacher <edick(a)idcomm.com>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Wednesday, October 20, 1999 12:33 PM
Subject: Re: OT: how big would it be?
the
Why not explore this problem from the standpoint
of an FPGA? When you
finish you'd still have the flexibility of a hand-built device, yet what
you
learned in the process would potentially be of
actual use?
(if this was directed at me)
I have to design that kind of crap now, every day. I just got *into*
transistor computers and find it quite interesting to see what games I can
play with old RTL type stuff.
>Why squander your cash and intellectual resources on creating something folks in the
'70's electronics industry were striving to avoid when you
could have the same mental exercise in a productive form that made the
design and implementation of your architecture the core of your effort
rather than issues which are no longer relevant, like power consumption,
packaging, and finding the appropriate materials from which to build your
device? Signal routing is the one issue which persists from that era of
yesteryear when a CPU lived in multiple racks, but it's handled, at least
superficially, by the development software. Sharing flipflop packages or
gates between two circuits on a backplane with 50 cards of logic in it is
no
easy matter. What's more, the propagation
delays will slow your circuit
down to cycles in multiple microseconds, while correcting the associated
routing errors will take multiple days for each one. While it's not
perfect, the FPGA approach allows you to have these experiences with a
"virtual" closet-sized backplane with similarly "virtual" cards
(modules)
of
logic which you can design hierarchically and
based on your needs, not on
what the local parts vendor happens to have.
I design high speed logic (some basic config cpu cores) now using Xilinx even some AMD chips (yes, I use to use the MACH stuff)
all with various
RISC
chips. I don't want to come home at night and
*continue* the same type of
design work (or code). I find it more entertaining to work on an 8/S , not
drop one in a chip [though that might be interesting]. I try to spend my
time on the old systems which is what taught me back in '79 so much about
the new ones.
This unit will be nothing more than a conversation piece (in my office,
hopefully doing some small task) and I hope to have some fun with quick and
dirty logic.
If my PDP-8/S wasn't so *mint* in the rack I'd rip it out, drop it in a 8/E
table top case and drag it into the office to do something fun.
john
transistors
>>required. How many transistors did an 8080 have? (Do remember, however,
>>that the transistor count is actually less than you'd need with discrete
>>transistors, because the on-chip transistors can have multpile emitters
or
Dick
-----Original Message-----
From: Mike Cheponis <mac(a)Wireless.Com>
To: Discussion re-collecting of classic computers
<classiccmp(a)u.washington.edu>
Date: Wednesday, October 20, 1999 9:35 AM
Subject: Re: OT: how big would it be?
>> > Say someone were to home-build a CPU from scratch using only
individual
> >
components, no ICs only modern discrete(?) components. How big would
the
> > CPU be? For comparison lets say it
would be an 8080 clone. Any
guesses?
>
>It seems to me the Right Answer is to approximate the number of >>gates or whatever in the same device.)
>>
>>As for how "big" it would be (that is, its size), modern discrete
>transistors
>>are available in tiny SOT-23 or even tinier packages. Resistors are
>>available in 0402 and maybe smaller. Line widths on PC boards can
perhaps
>be as small
as .002 inches, and they can be many layers, a dozen or more.
>
>So, in order to compute the size, I think you'd need to make two
estimates:
>
>1) The number of transistors per cubic inch (or cm if you like those
units)
2) The number of transistors required.
This assumes some packaging/connector allowance is taken into account to
estimate the number of transistors per cubic whatever.
------
IMHO, if you're going to build something from transistors, why not build
something that was originally built with transistors? For example, the
IBM 1620, 1130, 1401, etc. Or if you really want to get funky, try
something
>like transistorizing a tube machine, like ENIAC or JOHNNIAC or Bendix -That-
could be entertaining...
-Mike Cheponis