13 Mar
2025
13 Mar
'25
7:36 p.m.
On Mar 13, 2025, at 3:28 PM, ben via cctalk
<cctalk(a)classiccmp.org> wrote:
On 2025-03-13 12:24 p.m., Martin Bishop 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.
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.
paul
One FPGA will easily do a VLIW sequencer + scalar
mills (one or more, memory / MAC assemblies) or a simple processor
When it works.
I see lots low cost Chinese FPGA cards, so that is valid option.
Something like
https://www.aliexpress.com/item/1005005779045608.html provides a wholly adequate platform
for a microcoded processor, with lots of 3v3 IO for external logic analysis inputs
They goofed on that, 3 volt transistor logic is negative. :)