3 Nov
2005
3 Nov
'05
4:39 a.m.
Subject: Re: FPGA VAX update, now DIY TTL computers
From: "Chuck Guzis" <cclist at sydex.com>
Date: Wed, 02 Nov 2005 22:41:42 -0800
To: cctalk at classiccmp.org
On 11/3/2005 at 7:00 AM Jos Dreesen wrote:
As they say in some parts "it depends". ;)
I can think of three reasons to build a machine.
Recreate a system that is scarce or unobtainium such as the Apollo Block
One. Speed here is possibly important to understanding what it's limitiations
or capabilities were.
Experiment with an archetecture that may exist but is not a chip. Some speed
would be nice here as you may end up running real code.
Or just to build a computer that one can completely understand why and how
it works. Here speed is not essential, slow may aid is seeing all the bits
work in real time.
It would be hard to beat commercial hardware. However there is little
reason for not pushing the logic some if you plan to run an OS on it.
At the other extreme the ability to go glacially slow is a good debug
tool (all them lights don't hurt either).
Allison
Much too big to actually build in TTL.
Consider the very old Packard Bell PB250--22 bit words, fewer than 400
transistors and 2500 diodes, 63 instructions. Power consumption about 40
watts, exclusive of I/O:
http://ed-thelen.org/comp-hist/BRL61-p.html
The trick, of course, is to use bit-serial methods. It seems to me that
one could greatly simplify construction of a homebrew machine that way.
We're not doing this for speed, right?
Cheers,
Chuck