Search found 40 matches

by steve
24 Aug 2020, 11:37
Forum: Hardware and software hacking
Topic: microtron
Replies: 42
Views: 5544

Re: microtron

The 867 seems from 1982 and still in production! Despite not reducing logic gates, replacing the four X and PC incrementers with two 867 might reduce even further chip count also in "standard gigatron" (as a "type 1" change with full hw/sw compatibility). And without external carry ripple might be e...
by steve
21 Aug 2020, 18:39
Forum: Hardware and software hacking
Topic: microtron
Replies: 42
Views: 5544

Re: microtron

Up only: 74xx461, 463, 590, 591, 592, 593 Up and down: 74xx469, 579, 869, 867 74HC(T)590 should be the most common one. Wonderful! So any of them can in general be used for the VGA low address! The 74xx461 as I was mentioning before is very interesting and with the potential to replace 4 ICs of X a...
by steve
21 Aug 2020, 06:36
Forum: Hardware and software hacking
Topic: microtron
Replies: 42
Views: 5544

Re: microtron

klf wrote:
20 Aug 2020, 17:25
74HC393 is a ripple counter, like the 4040. Better use a 74HC163.
The 163 has the preset capabilities that are not used in this case but is just 4 bit, so 2 chips will be required. There is no other option for a single chip 8-bit counter fast enough (with preset capabilities or not)?
by steve
20 Aug 2020, 15:23
Forum: Hardware and software hacking
Topic: microtron
Replies: 42
Views: 5544

Re: microtron

You probably want to look at the 161/163 synchronous counters for doing memory addressing. The 4040 ripple counters have a 35ns propagation delay per flip-flop. The clock needs to transition through 18 stages to get to the MSB in this circuit. This is around 630ns to change from the clock edge whic...
by steve
18 Aug 2020, 20:32
Forum: Hardware and software hacking
Topic: microtron
Replies: 42
Views: 5544

VGA schema

Trying to be a bit more concrete for the VGA circuit idea I tryed to depict the circuit in kikad (have mercy please, is my first time for me drawing a circuit). screen.jpg The low address counter is using the main clock (that for now runs at around VGA dot /4), and the reset should be at 200 (=800/4...
by steve
18 Aug 2020, 18:52
Forum: Hardware and software hacking
Topic: microtron
Replies: 42
Views: 5544

Re: microtron

I must say, that seems like a little bit of genius. I especially like the first comment saying it won't work. A brave choice of words to place under a photo of it working. II would expect it to maybe a little temperamental. Infact pretty boldish, and many considerations he put out were proved wrong...
by steve
18 Aug 2020, 18:29
Forum: Hardware and software hacking
Topic: Ye Olde Gigatron and Gigatronski
Replies: 8
Views: 1264

Re: Ye Olde Gigatron and Gigatronski

The Soviet chips also have a different pin spacing (2.5mm instead of 2.54mm). But I was able to (gently!) get them all into their sockets, even the larger ones. I did spend quite some time looking for Soviet replacements of the 62256 SRAM and 27C1024 EPROM, but don't believe they ever existed. The ...
by steve
14 Aug 2020, 12:34
Forum: Hardware and software hacking
Topic: microtron
Replies: 42
Views: 5544

Decoupling VGA signal generation

I've found a very interesting article on generating full vga signal via a single counter and few other components: https://hackaday.io/project/9782-nes-zapper-video-synth-theremin/log/32271-vga-sync-generation With the consideration of Alastair to access the graphic memory pages on alternating clock...
by steve
04 Aug 2020, 21:56
Forum: Hardware and software hacking
Topic: microtron
Replies: 42
Views: 5544

Re: microtron

I have a project page on Hackaday . There's also a Git Repo with the current build tools. The ALU lookup tables are built with this Ruby script (outputs Intel HEX). It's still a work-in-progress, but I hope to have a completed version by the end of this month. I had a look at it and... I was impres...
by steve
04 Aug 2020, 18:54
Forum: Hardware and software hacking
Topic: vCPU instruction frequency
Replies: 5
Views: 952

Re: vCPU instruction frequency

Just updated native instruction frequency with actual instruction code: hex frequency % cum instruction --- --------- --- --- --------------- 5d 231666880 37% 37% ora [Y,X++],out c2 43701745 7% 44% st [nn] 01 33627338 5% 49% ld [nn] 0d 26085751 4% 54% ld [Y,X] 00 24871641 4% 58% ld nn 80 19154237 3%...