Less than 2 MB ChipMem is shifted up by 16 kB problem?

PeterK · 31 January 2017, 01:27

Hi Toni,

I found a problem when the ChipMem setting in WinUAE is less than 2 MB. In ShowConfig the memory chunk always appears to be shifted up by 16 kB. If the ChipMem size is 2 MB then the upper boundary is correctly set to the limit of 2 MB, too. But if the ChipMem size is less than 2 MB then the upper boundary is also pushed up by 16 kB.

Now the problem: as soon as all the memory below 1.5 MB, 1 MB, 512 kB or 256 kB is allocated and you are trying to allocate more ChipMem a lot of Enforcer hits are coming up telling me that invalid reads or writes are occuring and the system freezes or crashes sooner or later. If you use MEMF_REVERSE for ChipMem WinUAE crashes right from the start.

It seems to me that these upper 16 kB of ChipMem don't exist or are not really accessible. Could you please check that. Thank you.

If the ChipMem size is set to 2 MB everything works just fine and there are no problems with lowmem handling at all.

ReadOnlyCat · 31 January 2017, 04:58

Before Toni gets to read your message.

These information are missing from your post :
- version of WinUAE used
- emulation config

Without these, there is no guarantee of reproducing the issue.
A bug can only be fixed if it can be reproduced.

(Well, in this particular case, this is specific enough to point at a very particular piece of code but even then, there might be subtleties which make the piece of code responsible for this issue hard to find, so clear repro config is essential.)

Toni Wilen · 31 January 2017, 08:38

Sounds like direct JIT being annoying. Try without it.

PeterK · 31 January 2017, 10:27

You're right, Toni !

Indirect Jit fixes it, but please let it work with direct Jit, too.

It does not depend on the WinUAE version. I'm using 3.3.0 64 bit.

DamienD · 31 January 2017, 11:26

Slightly off topic and I'm sure this has been answered somewhere previously... I don't really use JIT but what's the difference between "direct" and "indirect"?

PeterK · 03 February 2017, 23:11

@Toni
I don't have a working Amiga anymore, but I asked the users at A1k.org how the ChipMem chunks are configured on their Amigas.

On an A2000 the 1 MB ChipMem uses the range $4000-$FFFFF, so the upper 16 kB don't exist like under WinUAE. Maybe, it's the most compatible solution to just cut off these upper 16 kB from the ChipMem chunks instead of getting a headache from searching for a direct Jit solution.

Toni Wilen · 06 February 2017, 18:13

This is now worked around but there is no guarantee it does not cause side-effects (like crash if program does something stupid like execution "falling off" the end of chip ram in direct jit mode)

Note that 1.5M can never work with direct JIT. JIT does not like non-power of 2 memory sizes.

Direct JIT = when translating m68k code to x86 code, direct jit compatible memory "bank" accesses are translated to x86 code (single instruction) instead of calling UAE memory bank access functions (lots of instructions). Increases speed greatly but can cause problems if programs do stupid things.

PeterK · 06 February 2017, 21:07

Thank you, Toni !

But where do you release the new beta versions now? I can't see any 3.5.0bxxx yet.

DamienD · 06 February 2017, 21:10

Quote:

Originally Posted by PeterK

But where do you release the new beta versions now? I can't see any 3.5.0bxxx yet.

http://www.winuae.net/files/b/winuae.7z

PeterK · 06 February 2017, 21:29

Thanks DamienD !

It seems to work now during the very first lowmem tests.

PeterK · 04 June 2017, 04:28

Quote:

Originally Posted by PeterK

Thank you, Toni !

But where do you release the new beta versions now? I can't see any 3.5.0bxxx yet.

Well, now I found it:
http://eab.abime.net/showthread.php?t=85939

31 January 2017, 01:27	#1
PeterK Registered User Join Date: Apr 2005 Location: digital hell, Germany, after 1984, but worse Posts: 3,365	Less than 2 MB ChipMem is shifted up by 16 kB problem? Hi Toni, I found a problem when the ChipMem setting in WinUAE is less than 2 MB. In ShowConfig the memory chunk always appears to be shifted up by 16 kB. If the ChipMem size is 2 MB then the upper boundary is correctly set to the limit of 2 MB, too. But if the ChipMem size is less than 2 MB then the upper boundary is also pushed up by 16 kB. Now the problem: as soon as all the memory below 1.5 MB, 1 MB, 512 kB or 256 kB is allocated and you are trying to allocate more ChipMem a lot of Enforcer hits are coming up telling me that invalid reads or writes are occuring and the system freezes or crashes sooner or later. If you use MEMF_REVERSE for ChipMem WinUAE crashes right from the start. It seems to me that these upper 16 kB of ChipMem don't exist or are not really accessible. Could you please check that. Thank you. If the ChipMem size is set to 2 MB everything works just fine and there are no problems with lowmem handling at all. Attached Thumbnails Last edited by PeterK; 31 January 2017 at 01:35.

31 January 2017, 10:27	#4
PeterK Registered User Join Date: Apr 2005 Location: digital hell, Germany, after 1984, but worse Posts: 3,365	You're right, Toni ! Indirect Jit fixes it, but please let it work with direct Jit, too. It does not depend on the WinUAE version. I'm using 3.3.0 64 bit. Last edited by PeterK; 08 February 2017 at 14:54.

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31 January 2017, 04:58	#2
ReadOnlyCat Code Kitten Join Date: Aug 2015 Location: Montreal/Canadia Age: 52 Posts: 1,178	Before Toni gets to read your message. These information are missing from your post : - version of WinUAE used - emulation config Without these, there is no guarantee of reproducing the issue. A bug can only be fixed if it can be reproduced. (Well, in this particular case, this is specific enough to point at a very particular piece of code but even then, there might be subtleties which make the piece of code responsible for this issue hard to find, so clear repro config is essential.)

31 January 2017, 08:38	#3
Toni Wilen WinUAE developer Join Date: Aug 2001 Location: Hämeenlinna/Finland Age: 49 Posts: 26,505	Sounds like direct JIT being annoying. Try without it.

31 January 2017, 11:26	#5
DamienD Banned Join Date: Aug 2005 Location: London / Sydney Age: 47 Posts: 20,420	Slightly off topic and I'm sure this has been answered somewhere previously... I don't really use JIT but what's the difference between "direct" and "indirect"?

03 February 2017, 23:11	#6
PeterK Registered User Join Date: Apr 2005 Location: digital hell, Germany, after 1984, but worse Posts: 3,365	@Toni I don't have a working Amiga anymore, but I asked the users at A1k.org how the ChipMem chunks are configured on their Amigas. On an A2000 the 1 MB ChipMem uses the range $4000-$FFFFF, so the upper 16 kB don't exist like under WinUAE. Maybe, it's the most compatible solution to just cut off these upper 16 kB from the ChipMem chunks instead of getting a headache from searching for a direct Jit solution.

06 February 2017, 18:13	#7
Toni Wilen WinUAE developer Join Date: Aug 2001 Location: Hämeenlinna/Finland Age: 49 Posts: 26,505	This is now worked around but there is no guarantee it does not cause side-effects (like crash if program does something stupid like execution "falling off" the end of chip ram in direct jit mode) Note that 1.5M can never work with direct JIT. JIT does not like non-power of 2 memory sizes. Direct JIT = when translating m68k code to x86 code, direct jit compatible memory "bank" accesses are translated to x86 code (single instruction) instead of calling UAE memory bank access functions (lots of instructions). Increases speed greatly but can cause problems if programs do stupid things.

06 February 2017, 21:07	#8
PeterK Registered User Join Date: Apr 2005 Location: digital hell, Germany, after 1984, but worse Posts: 3,365	Thank you, Toni ! But where do you release the new beta versions now? I can't see any 3.5.0bxxx yet.

06 February 2017, 21:29	#10
PeterK Registered User Join Date: Apr 2005 Location: digital hell, Germany, after 1984, but worse Posts: 3,365	Thanks DamienD ! It seems to work now during the very first lowmem tests.

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