Search found 15 matches

by Lerc
01 Jul 2022, 22:16
Forum: Hardware and software hacking
Topic: Musings on compatibility breaking changes.
Replies: 4
Views: 134

Re: Musings on compatibility breaking changes.

A couple of issues with your theoretical code: 1) You add 1 to the high byte for both carry and non carry paths, because of the branch delay slot after bra .done . Moving the bra one instruction up would solve this problem. 2) You have different cycle timings for the two carry paths, this could be ...
by Lerc
28 Jun 2022, 14:46
Forum: Hardware and software hacking
Topic: Musings on compatibility breaking changes.
Replies: 4
Views: 134

Musings on compatibility breaking changes.

So I have had quite some time to ponder the architecture of the Gigatron and ways it could be modified for more capabilities. Almost any enhancement that could be made to the Gigatron would add chips. From my perspective I'm ok with that provided it is done sparingly with substantial benefit to be g...
by Lerc
28 Jun 2022, 07:04
Forum: Hardware and software hacking
Topic: Gigatron Clone Ideas
Replies: 46
Views: 1669

Re: Gigatron Clone Ideas

I agree with @at67 though. Breaking compatibility is a rabbit hole I don't want to go down. Fair enough, It's a rabbit hole that I'm peering into (which is why I've been looking at what instructions are actually used) and I can fully understand the trepidation. I might start a new thread for some o...
by Lerc
28 Jun 2022, 06:33
Forum: Hardware and software hacking
Topic: Gigatron Clone Ideas
Replies: 46
Views: 1669

Re: Gigatron Clone Ideas

2x VGA? Is that running 120Hz with 63Khz ScanLines? If so, that's a pretty clever RF adapter.
by Lerc
21 Jun 2022, 22:13
Forum: Hardware and software hacking
Topic: Gigatron Clone Ideas
Replies: 46
Views: 1669

Re: Gigatron Clone Ideas

I did a quick scan of The V5a ROM to see what Instructions were used https://gist.github.com/Lerc/2af74fde9f4aab0e88d65b0f22950622 It found 6 instances of jmp [Imm] e1xx 6 It wouldn't be the end of the world to break backwards compatibility and to break the jmps into multiple (2) instructions. The R...
by Lerc
08 Jun 2022, 16:42
Forum: Hardware and software hacking
Topic: Circuit simulator
Replies: 3
Views: 138

Re: Circuit simulator

I run it at 100Hz. The first led Lights up after about a minute. Then there is quite a long wait (15 min) while it does the entropy gathering code. You should be able to see X and Y count through the full range of memory while it does this.
by Lerc
08 Jun 2022, 08:09
Forum: Hardware and software hacking
Topic: Circuit simulator
Replies: 3
Views: 138

Circuit simulator

So I made this thing [attached I hope]. It's a Gigatron laid out in SimulIDE https://www.simulide.com CircuitScreenShot.png It has been a tough job debugging but I got it to the point where It runs through the boot process and lights up the blinkenlights in order and eventually jumps off to $1200 to...
by Lerc
24 Aug 2020, 21:09
Forum: Hardware and software hacking
Topic: microtron
Replies: 42
Views: 20516

Re: microtron

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 even marginally faster. The 5...
by Lerc
16 Aug 2020, 21:05
Forum: Hardware and software hacking
Topic: microtron
Replies: 42
Views: 20516

Re: microtron

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 I must say, that seems like a little bit of genius. I especially like the first comment s...
by Lerc
27 Jul 2020, 21:07
Forum: Hardware and software hacking
Topic: microtron
Replies: 42
Views: 20516

Re: microtron

I'm not sure I got this point (what exactly to OR and for what reason), but let me say that I would probably prefer suggestions to remove chips than to add if possible! :D The OR combining would be for using two 8 bit inputs instead of nibbles on Load W. It would let you do operations where bits in...