Doom Video glitch problem "SOLVED"

[Imperious]

Apologies for the delay, got sidetracked with other retro computer stuff.

I don't seem to get any errors at all from what I can tell, the program was running well over 15 minutes in a loop (video clip cut short deliberately).
Youtube vid attached. Let me know if I stuffed it somehow by modifying the wrong lines.
Couple of typo's but the "1" key is a bit dodgy on my keyboard.

[youtube]k0qKEzCbPUI[/youtube]

[Imperious]

It's taken me an awful lot of time and brain energy to finally figure out the cause of this problem, and in a way I am pretty
annoyed at myself as to the cause, but at the same time I have learn't bucketloads about how the Vic-20 works so definitely not
wasted time in that respect.
I even went down the unlikely path of redesigning the chip and block select part of the 32k memory expansion to use a 74hc21 as a
4 to 1 AND gate for the chip select, and a 74hct00 as the block select. At the moment the unused pins are floating, so I'll deal with that
if and when I get any problems. I had an idea that separating the ouputs of chip select and block select to different IC's might help.
Made no difference of course but I was clutching at straws. A different brand of Ram chip also made no difference, Alliance vs Cypress.

I have spares for every single IC in the Vic-20 so tried sitting new chips on top of their equivalent, that made no difference. Ram tests all passed
with flying colours. My Vic-20 had no problems with Kweepa's game "The Keep" so that proved there couldn't really be a video related problem as
both games appear to the untrained eye to have a similar style of drawing the graphics.

Where I mentioned this earlier "Another weird behaviour is I was testing the Text Colour change in basic by pressing CTRL-Number keys and occasionally got letters instead."
I got the same behaviour in Vice when I tried that a couple of days ago.

As it turns out there wasn't a single fault anywhere whatsoever inside my Vic, every part working perfectly.

The Moral of the story and Answer to the problem is "DO NOT USE A 65C02" processor as a 6502 replacement. As I got a couple of these very cheap
on Ebay to try and resolve intermittent crashing issues and left it installed as they run nice and cool.

So I'll probably order a couple of R6502's as spares, if there are any compatibility issues there that anyone knows about please let me know?

[Jeff-20]

Off topic, how are you capturing the video above?


Sent from my iPhone 6 Beta using Tapatalk

[Imperious]

I have an Avermedia H727 capture card in my PC, it has Analog and Digital tv. Composite, s-video, component, and Hdmi inputs.

I captured that through s-video from my Vic-20 with the Avermedia software which is absolute rubbish except capture functions produce a decent result.
The Digital TV is so bad I installed Mediaportal which is a Lot better.

[tokra]

The Moral of the story and Answer to the problem is "DO NOT USE A 65C02" processor as a 6502 replacement. As I got a couple of these very cheap
on Ebay to try and resolve intermittent crashing issues and left it installed as they run nice and cool.

I don't think the 65C02 does undocumented opcodes, does it? They are being used in Doom if I am correct: Doom code improvement-discussion

[Imperious]

You are correct, the 65C02 doesn't do undocumented opcodes, there were also other changes.

Doom was the only game I tried that gave problems, although there is still a lot of software I haven't tried.

Interestingly whilst doing some research about this I found out that when the Apple2C was released it broke some of
the software, which is because it used a 65C02.

[Kweepa]

Yeah, I use ASR in the column renderer. See the sources on github:
https://github.com/Kweepa/vicdoom/blob/ ... olumnAsm.s
lines 70, 71.
Seems like a poor choice now, since it didn't make things appreciably faster...

[rhurst]

I wonder if VICE will support swapping out a 6502 with a 65C02 to reproduce this mod?