Search found 268 matches

by marcelk
18 Jun 2019, 23:36
Forum: Hardware and software hacking
Topic: Smallest vCPU program
Replies: 0
Views: 45

Smallest vCPU program

The smallest vCPU application 1. Gives identifiable visual feedback: - Draws two colored lines (one vertical, one horizontal) - Continuously blinks a pixel 2. Is interactive: - Shifts the screen when a button is pressed, restores when released - Changes line color when this button is an arrow button...
by marcelk
17 Jun 2019, 11:19
Forum: Hardware and software hacking
Topic: v6502
Replies: 7
Views: 279

Re: v6502

A bit more debugging done, and larger programs are possible. Video link: https://youtu.be/9jHlEjr7xJk munch.jpg #$85 #$30 { munch sta $30 } #$a9 #$00 { lda #0 } #$85 #$31 { sta $31 } #$a9 #$10 { lda #16 } #$85 #$32 { sta $32 } #$a9 #$18 { nextT lda #$18 } #$85 #$33 { sta $33 } #$a5 #$33 { nextY lda ...
by marcelk
16 Jun 2019, 13:58
Forum: Kit assembly
Topic: Another successful build!
Replies: 1
Views: 42

Re: Another successful build!

Great, please share a picture!

The quote comes from one of Oscar's talks on designing the PiDP-8 kit: https://www.youtube.com/watch?v=cWRDxANRT-I (at the 18:30 mark)
by marcelk
15 Jun 2019, 13:59
Forum: Hardware and software hacking
Topic: v6502
Replies: 7
Views: 279

Re: v6502

Are there any low hanging fruit - where a native Gigatron instruction performs an exact equivalent of a 6502 instruction? Not really, but there's not much overhead in the emulation either. The 6502 instruction set is more orthogonal than I remembered, and decoding was easier than expected. Implemen...
by marcelk
15 Jun 2019, 12:42
Forum: Hardware and software hacking
Topic: v6502
Replies: 7
Views: 279

Re: v6502

Having looked through some of the code, I could see that to emulate a 6502 and keep it within the timing constraints of the video generation is no small undertaking. For personal reasons I can't spend much time on these projects recently. I needed a break from tackling the C compiler register alloc...
by marcelk
15 Jun 2019, 11:56
Forum: Hardware and software hacking
Topic: v6502
Replies: 7
Views: 279

Re: v6502

There is one thing which I dearly miss in both cores, and that is interrupt handling - NMI or normal IRQs - within 'reasonable' latency. It doesn't need to be cycle-exact, as long the user-level end-purpose - reliable working input and output - is reached. I would do that by polling the signals of ...
by marcelk
14 Jun 2019, 23:30
Forum: Hardware and software hacking
Topic: v6502
Replies: 7
Views: 279

v6502

I just pushed into GitHub some experimental code that might become part of the platform: a 6502 emulator. This is very much work in progress, based on an idea I was pondering about for a while and that needed to get out. v6502 is a MOS 6502 emulator written in 8-bits native Gigatron code, and that c...
by marcelk
08 Jun 2019, 13:56
Forum: Hardware and software hacking
Topic: ROMv3.py "Execute this to build ROM files" doesn't work
Replies: 1
Views: 59

Re: ROMv3.py "Execute this to build ROM files" doesn't work

The .py file itself contains the kernel loops and SYS functions (and images, but I think I will change that at some point). You need to announce the higher level stuff that you want to include with the ROM (applications) on the command line. The ROM builder will then put these in the cold storage po...
by marcelk
08 Jun 2019, 10:17
Forum: Kit assembly
Topic: board testing
Replies: 40
Views: 896

Re: board testing

Update for forum readers: We took the troubleshooting offline. The board now works fine after finding a pin that was bent instead of going through its hole. (And some other issues not worth mentioning here.)

IMG_5266 copy.jpeg
IMG_5266 copy.jpeg (119.11 KiB) Viewed 30 times

Now you know why we presocket the RAM and EPROM chips :-)
by marcelk
06 Jun 2019, 12:46
Forum: Hardware and software hacking
Topic: High resolution mode?
Replies: 28
Views: 1719

Re: High resolution mode?

I think the vertical lines are due to the propagation delay of the register. When clock changes to high the multiplexer switches first, showing a wrong value before new valid data comes out a few nanoseconds later. Also the multiplexer is built around AND/OR gates, and there are transients when the...