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chatGPZ
Registered: Dec 2001
Posts: 11510 |
Testers needed: unemulated DMA Delay Artefacts
Steve West has reported some interesting findings on yet unemulated DMA Delay Artefacts, see here
We need to collect more data here. If you are able to open up your C64 so you can report back the ASSY and the VICII type, please take a couple minutes and do the following:
- run the vsp-tester.prg (or vsp-tester-ntsc.prg) from here
- report the ASSY and the exact markings on the VICII
The program will display the detected address, and show green border if that address is known good, or red border if not.
- report the border color, and the address it shows
Interesting are tests on all kind of C64s and Videochips, we need to confirm (or not) how certain values are related to certain videochips.
(For those who care: this could be a working emulator detection for a while)
TIA! |
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chatGPZ
Registered: Dec 2001
Posts: 11510 |
We might be able to answer if this is an realistic option - if more people run those tests :) |
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JackAsser
Registered: Jun 2002
Posts: 2038 |
Quote: Quoting JackAsserThis would explain an artefact I never could get rid of in the scroller below the hidden line vector in 1991 (only visible on some c64s). Would these findings have helped back then? I.e., clearing not only $3FFF but also $38FF, $3BFF, etc.?
Actually setting, not clearing. I wanted a black line, but one char of the IDLE-line had background pixels showing when we tried on Hednig's computer during the party. |
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Krill
Registered: Apr 2002
Posts: 3083 |
Quoting JackAsserActually setting, not clearing. I wanted a black line, but one char of the IDLE-line had background pixels showing when we tried on Hednig's computer during the party. Still sounds like a "yes, probably" to me. =) |
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JackAsser
Registered: Jun 2002
Posts: 2038 |
Quote: Quoting JackAsserActually setting, not clearing. I wanted a black line, but one char of the IDLE-line had background pixels showing when we tried on Hednig's computer during the party. Still sounds like a "yes, probably" to me. =)
Yup! Maybe Hedning can find that computer again and test the demo again, then I'll do a patch and retest. |
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Krill
Registered: Apr 2002
Posts: 3083 |
Quoting JackAsserYup! Maybe Hedning can find that computer again and test the demo again, then I'll do a patch and retest. FWIW, i too stumbled over that issue here and there. Took it as a given and just covered it up with a sprite or something. =)
But if/when you need to set all 16 bytes at $3xFF... mmmh. |
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chatGPZ
Registered: Dec 2001
Posts: 11510 |
The tests showed other bytes than that too :) |
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JackAsser
Registered: Jun 2002
Posts: 2038 |
Quote: The tests showed other bytes than that too :)
Wonder if the internal pullups on the adress lines are too weak when it releases the bus. (It = VIC) |
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chatGPZ
Registered: Dec 2001
Posts: 11510 |
My guess would be that it is related to propagation delays in the the chip, not external bus |
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Digger
Registered: Mar 2005
Posts: 447 |
You almost got me to believe that a new non-emulated DMA-0delay trick was just invented.
*Now need to wait until GPT 8 is released to discover it. |
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Cruzer
Registered: Dec 2001
Posts: 1049 |
PAL
ASSY No. 250425
MOS 6569R3 5185 S
Green, 38FF |
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