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_at_internet.look.ca>
To: Discussion re-collecting of classic computers
<classiccmp_at_u.washington.edu>
Date: Wednesday, October 20, 1999 11:06 AM
Subject: Re: OT: how big would it be?
>
>-----Original Message-----
>From: Richard Erlacher <edick_at_idcomm.com>
>To: Discussion re-collecting of classic computers
><classiccmp_at_u.washington.edu>
>Date: Wednesday, October 20, 1999 12:33 PM
>Subject: Re: OT: how big would it be?
>
>
>>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
the
>>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
and
>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
>
>
>>Dick
>>
>>-----Original Message-----
>>From: Mike Cheponis <mac_at_Wireless.Com>
>>To: Discussion re-collecting of classic computers
>><classiccmp_at_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
>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
>>>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
>G-15.
>>>-That- could be entertaining...
>>>
>>>-Mike Cheponis
>>>
>>
>
Received on Wed Oct 20 1999 - 15:09:51 BST
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