Search found 348 matches

by marcelk
10 Oct 2019, 17:43
Forum: Hardware and software hacking
Topic: v6502
Replies: 17
Views: 2736

Re: v6502

The whole thing is still a bit shaky, but now this significant part already works: we have floating point (just in time for VCF Berlin)!
by marcelk
08 Oct 2019, 16:16
Forum: Hardware and software hacking
Topic: Memory heatmap from GT1 files
Replies: 0
Views: 54

Memory heatmap from GT1 files

While solving GitHub issue #41 , and in figuring out where in RAM to put the SDC/MMC file loader, we got interested to learn where existing GT1 files tend to load. Answering this is not too hard when combining gt1dump.py, awk and gnuplot. The result is the heatmap attached. We can see nobody loads i...
by marcelk
07 Oct 2019, 15:58
Forum: Hardware and software hacking
Topic: 10MHz, 12.5MHz and Beyond!
Replies: 22
Views: 2353

Re: 10MHz, 12.5MHz and Beyond!

That ROM v3y hasn't changed. The programmed refresh rate is for 31.25 kHz at 12.5 MHz. So at that speed, shrink the displayed pixels... Last week I tested it again on my 15 MHz system after soldering the last color resistors (I had ran out of 820 Ohms). But then I found the game controller doesn't r...
by marcelk
07 Oct 2019, 11:51
Forum: Escape Meta Alt Control Shift
Topic: Modified Gigatron Design Ideas
Replies: 8
Views: 188

Re: Modified Gigatron Design Ideas

Where can I find such talks? They're all over the place by now :-). There's an early one on the Gigatron site's front page , and there's a recent one from Moscow in this subforum. So if that is just a line of pixels, then I could find a way to get them from memory and output them? Personally I have...
by marcelk
07 Oct 2019, 08:00
Forum: Hardware and software hacking
Topic: v6502
Replies: 17
Views: 2736

Re: v6502

Next stage of testing v6502 has to be Micro-Soft BASIC with floating point. We're not quite there yet as it goes awry after the memory check. But by reorganising the video indirection table we can squeeze in the entire 8.3 KB BASIC binary and don't have to compromise too much on screen space. We sho...
by marcelk
07 Oct 2019, 06:50
Forum: Escape Meta Alt Control Shift
Topic: Modified Gigatron Design Ideas
Replies: 8
Views: 188

Re: Modified Gigatron Design Ideas

Encoding is the binary form. It's code that bursts 160 pixels, and then turns to black. Walter's Gigatron talks explain practically everything about the native instruction set and video generation. I'm not familiar with Atari architectures (other than the 2600 :-)).
by marcelk
06 Oct 2019, 14:23
Forum: Escape Meta Alt Control Shift
Topic: Modified Gigatron Design Ideas
Replies: 8
Views: 188

Re: Modified Gigatron Design Ideas

I have not built a Gigatron yet. It seems very interesting. What I'd like to see is a way to get the video out of software and have dedicated circuitry for it. Now, generating sync pulses is the easiest. But I can't figure out where the pixels come from. The pixel burst is this snippet in ROM: addr...
by marcelk
05 Oct 2019, 22:58
Forum: Escape Meta Alt Control Shift
Topic: Summer + Hebden Bridge, Cambridge and Berlin
Replies: 13
Views: 496

Re: Summer + Hebden Bridge, Cambridge and Berlin

I believe we're ready for VCF Berlin next weekend
by marcelk
05 Oct 2019, 15:43
Forum: Hardware and software hacking
Topic: New vCPU instructions? (poll)
Replies: 6
Views: 680

Re: New vCPU instructions? (poll)

The development ROM has just received 3 experimental new vCPU instructions. These new ones are still mostly untested/concepts. But as such "open heart surgeries" can introduce unexpected problems elsewhere, I pushed them anyway so we have more chance to find regressions. Caveat emptor if you live on...