> On Mar 13, 2025, at 7:56 PM, Paul Koning via cctalk <cctalk@classiccmp.org>
> wrote:
>
>
>
>> On Mar 13, 2025, at 4:35 PM, ben via cctalk <cctalk@classiccmp.org> wrote:
>>
>> On 2025-03-13 1:36 p.m., Paul Koning via cctalk wrote:
>>
>>> Depends on which one. RTL was 3.6 volts positive, as far as I can
>>> remember. I actually have a keyboard that has some of those devices in it.
>>> Yes, ECL is around 3 volts also but negative supply. And of course some
>>> people designed systems with positive supplies but "negative" logic, in the
>>> sense that ~0 volts is logic 1 while near-VCC is logic 0; the CDC 6000
>>> series machines are an example.
>>
>> I was thinking of the PDP-8 there. 0 Volts logic 1 -3 volts logic 0.
>>
>>> FPGAs come in amazing sizes if you have sufficient money. I hope some day
>>> to cram an entire CDC 6600 into an FPGA. The main problem with this isn't
>>> FPGA sizes (by today's standards, an upper-midrange FPGA can do the job,
>>> memory included) but rather the creation of an accurate model given the
>>> bizarre and hairy timing of that machine. I have a gate level model, but
>>> it doesn't work yet because of those issues.
>>
>> What would the purpose of said computer be?
>> Might be better off with a clean 64 bit design and 16 bit bitslices.
>
> To understand fully how the 6000 machines work, ...
An additional comment on that. To understand any field well, it is generally
helpful, and at times crucial, to have some knowledge of early work. I just
read a translation of some of the works of Galileo that makes that point in so
many words in the introduction. Similarly, while people don't build compilers
today the way they did in 1960, it is still valuable to read how Dijkstra and
Zonneveld wrote the first ALGOL-60 compiler and, along the way, had to invent
many of the compiler construction techniques that were later routinely taught
and used in university compiler construction courses. There's an outstanding
analysis of that, in the Ph.D. thesis of Gauthier van den Hove. (It's not yet
a published document; I think that has something to do with copyright and
publication practices at some universities, perhaps Dutch or European
conventions.) He subtitled his thesis "New insights from old programs".
paul
