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Old 04 April 2012, 15:30   #1
PeterK
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Location: digital hell, Germany, after 1984, but worse
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Exclamation Very old JIT direct bug: 512 kB Chip reported as 1MB

There seems to be a very old bug with 512 kByte ChipMem which appears as 1MByte ChipMem instead to the Amiga OS (3.1) and leads to crashes, and this only happens with the JIT enabled and if running in "Direct" mode. Once the JIT has been disabled or switched to "Indirect" mode this issue never happens again until you restart WinUAE completely.

However, this is only a small bug, not very important for me, but by reporting this little issue here I would also like to take the chance to say THANK YOU to Toni for all the excellent work he is still doing to improve WinUAE constantly.

Update1: Added a comparison between JIT Direct (red) and Indirect (yellow) in the winuaelog.txt

Update2: This bug was introduced with WinUAE 1.0. The readme.txt of WinUAE 1.0 contains this note in its list of changes:

- improved JIT direct access memory area allocation (fixes JIT
direct mode problems with some Pentium 4 or NForce 3/4 boards)
Attached Thumbnails
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Name:	512kB_ChipMemBug.png
Views:	271
Size:	44.6 KB
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Name:	JitDirect-IndirectCompare.png
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ID:	31173  
Attached Files
File Type: txt winuaelog.txt (5.8 KB, 166 views)
File Type: txt winuaebootlog.txt (12.1 KB, 150 views)
File Type: uae FakedChipMem.uae (13.4 KB, 161 views)

Last edited by PeterK; 04 April 2012 at 18:13.
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Old 04 April 2012, 18:40   #2
Toni Wilen
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Join Date: Aug 2001
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Age: 46
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I think it was this one:

- DMA accesses to upper 512kb of chip RAM with only 512k chip RAM
and 1MB Agnus installed don't map to low 512kb like CPU accesses do.

JIT direct still "see" this hidden 512k region because JIT direct ignores all memory banks and mask.

Will be fixed in next beta.
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Old 04 April 2012, 22:08   #3
PeterK
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@Toni
Many thanks for this quick response. It works as it should, but I didn't expect anything else.

Last edited by PeterK; 06 April 2012 at 13:08.
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