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chatGPZ
Registered: Dec 2001
Posts: 11386 |
what is your RAM init pattern?
since i stumbled about yet another case of some ancient demo that relies on uninitialized RAM - and which would only work if you change the default VICE uses currently - i think its about time to collect some hard data about this phenomenon and perhaps at the end add proper configuration for it to VICE (or even choose a better default).
background: when you power on your C64, the RAM will not be zero, instead (about) half of the RAM cells will be 1, and the other half will be 0. this results in some kind of pattern (mostly) consisting of $00 and $ff. for example if you start VICE, then enter the monitor and look at a page of RAM it shows this:
(C:$e5d4) m c000 c0ff
>C:c000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
>C:c010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
>C:c020 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
>C:c030 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
>C:c040 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
>C:c050 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
>C:c060 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
>C:c070 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
>C:c080 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
>C:c090 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
>C:c0a0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
>C:c0b0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
>C:c0c0 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
>C:c0d0 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
>C:c0e0 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
>C:c0f0 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
this is the default pattern, which could be shortened to "64 times $00, 64 times $ff, repeat"
now i'd like to know how it looks like on your (real) C64... if you have some cartridge with ML monitor, all you need to do is power on your c64, check some memory page, and post the pattern here (you can ignore that some values wont actually be 0 or $ff - what matters is the general trend). additionally it would be extra cool if you could look into your C64 and post the type of RAM chips that it uses as well (since the pattern most likely depends on them) - they are labelled 4164 or 4464 or 41464 (please post everything written on it, the exact type and manufacturer is interesting here). Also please post the ASSY NO of the board, as the way RAM is wired up matters as well.
thanks for your help!
PS: if you are curious, Typical is the demo in question... if you can name other examples ("works in CCS64 but not in VICE is often an indicator for it), please post them too! |
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Flavioweb
Registered: Nov 2011
Posts: 463 |
Matter of superstition ...
usually we say: "do not touch the sleeping dog", which means: "if something is working, don't thouch it".
I am sure that if I opened them, something stop working ...
=P
PS: I'm not superstitious because it brings bad luck.
=D
Edit: i'm pretty sure that more old are the ram chips, more random values are included in the patterns... |
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chatGPZ
Registered: Dec 2001
Posts: 11386 |
could you tell the ASSY NO of that breadbin then at least, please? :) |
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Flavioweb
Registered: Nov 2011
Posts: 463 |
Assy n. 250407 artwork 251137 rev C. |
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chatGPZ
Registered: Dec 2001
Posts: 11386 |
updated
TMR/Karmic/Christopher Jam: could also make a memory dump? |
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Flavioweb
Registered: Nov 2011
Posts: 463 |
Just for the record, Typical works if in Vice we set "first byte: $00", "lenght of constant: 4" and "lenght of pattern: 8".
This create a pattern like:
.:c000 00 00 00 00 ff ff ff ff ........
.:c008 ff ff ff ff 00 00 00 00 ........
.:c010 00 00 00 00 ff ff ff ff ........
.:c018 ff ff ff ff 00 00 00 00 ........
.:c020 00 00 00 00 ff ff ff ff ........
.:c028 ff ff ff ff 00 00 00 00 ........
.:c030 00 00 00 00 ff ff ff ff ........
.:c038 ff ff ff ff 00 00 00 00 ........
.:c040 00 00 00 00 ff ff ff ff ........
.:c048 ff ff ff ff 00 00 00 00 ........
.:c050 00 00 00 00 ff ff ff ff ........
.:c058 ff ff ff ff 00 00 00 00 ........
.:c060 00 00 00 00 ff ff ff ff ........
.:c068 ff ff ff ff 00 00 00 00 ........
.:c070 00 00 00 00 ff ff ff ff ........
.:c078 ff ff ff ff 00 00 00 00 ........
.:c080 00 00 00 00 ff ff ff ff ........
.:c088 ff ff ff ff 00 00 00 00 ........
.:c090 00 00 00 00 ff ff ff ff ........
.:c098 ff ff ff ff 00 00 00 00 ........
.:c0a0 00 00 00 00 ff ff ff ff ........
.:c0a8 ff ff ff ff 00 00 00 00 ........
.:c0b0 00 00 00 00 ff ff ff ff ........
.:c0b8 ff ff ff ff 00 00 00 00 ........
.:c0c0 00 00 00 00 ff ff ff ff ........
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MagerValp
Registered: Dec 2001
Posts: 1078 |
https://www.dropbox.com/s/f7anwdudabcd9f4/Foto%202016-04-29%202..
https://www.dropbox.com/s/xzf5so80buvx62w/Foto%202016-04-29%202.. |
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chatGPZ
Registered: Dec 2001
Posts: 11386 |
flavioweb: for typical the only thing that is needed is that $3fff is 0 (or perhaps even something different to $ff) :) |
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willymanilly
Account closed
Registered: Jan 2016
Posts: 27 |
My C64C PAL (ASSY 250466) with Action Replay VI connected has the following power on ram values:-
0000-3fff 128 times $ff, 128 times $00, repeat
4000-7fff 128 times $00, 128 times $ff, repeat
8000-bfff 128 times $00, 128 times $ff, repeat
c000-ffff 128 times $ff, 128 times $00, repeat
There are some random bytes in the above patterns, mainly with the 4 LSB's of those bytes.
I got the same results without AR connected. |
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Pitcher
Registered: Aug 2006
Posts: 61 |
Cars in the garage tomorrow morning, I'll dig my 2 out and have a look, both breadbins but with completely different boards. |
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chatGPZ
Registered: Dec 2001
Posts: 11386 |
willymanilly: could you check what type of RAM is on that board, please? |
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