Virtual Memory

[morfan@calvin.info.unicaen.fr (Eddy Morfan)]

Hi there,

I'm currently including virtual memory features in a MiNT kernel (1.12.h3).

This will allow use of virtual RAM space as TT RAM and keep memory protection
enabled (in fact it works only with memory protection).
All Kernel memory management and bus error (for page default) have been changed.
I'm now working on the disk space routs which should allow use of a dedicated 
hard drive partition and/or a file (maybe, as a don't see actually how to
protect it).
I have two problems :
1) As the "mint.cnf" file is loaded after memory and file systems configuration,
   how can I configure the virtual memory ?
2) The handling of the TT RAM by applications and the TOS isn't correct :
   The VDI uses TT RAM for bit blocks so that when you really have TT RAM the 
   Blitter gets confused as it's address bus is 24 bits wide !
   This didn't matter until yet because the only machines with TT RAM didn't
   have any Blitter. But using a Falcon with TT RAM will result in making the
   Blitter chip reading/writing in a wrong memory place if the given address is
   in TT RAM ( it will use only the 24 least significants bits !).
   This could be solved by using only ST RAM for bitblocks but it would be a bit
   complex to force both the ROM-OS and the Multitasking AES using ST-RAM.
   It would be also necessary to make applications which have icons/bitmaps in 
   their data segment load in ST-RAM (so no virtual memory for them !). AES
   ressources should also be loaded in ST-RAM. It's obvious that using this
   method will result in having many situations where the virtual memory could
   not be used. So the solution could be to use the Blitter only when the data
   are in ST-RAM, but we are not the VDI. I also discovered a bug in AES 4.1 
   Desktop : it always loads an application in TT-RAM even if its header
   indicates that it must be loaded in ST-RAM.
   This problem occures with the Blitter chip as well as the DMA-Sound and other
   similar DMA chips. With another chip, this doesn't really matter, but the 
   Blitter problem is the worst as it depends on the OS.

Please anywone makes any suggestions and/or comments.

That's all, thanks, Eddy.

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| Eddy MORFAN      ( Email : morfan@info.unicaen.fr )                 |
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| Atari STf    2.5Mo                                                  |
| Atari Falcon 030/4Mo/340Mo                                          |
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