Re: Virtual Memory (Was Re: Kernel 1.14.7 available)

[Anthony Jacques <jacquesa@zetnet.co.uk>]

Hiya

> I don't know how far your new VM is from ready, but if your aim is to change it
> completly I think I can help you, as I did a patch some years ago to let my MiNT
> kernel use virtual memory. It works on my Falcon and has some interesting 

This sounds like a really nice patch. 

> I didn't release it because of a TOS- 4.04 bug wich I wasn't able to solve fast
> enough:
> whatever xbios call you do the Blitter is always enabled by the Xbios, and the
> Multitos AES allocates its buffers from TT-RAM (the only place I handled V-RAM
> as TT-RAM was in TOS Mxalloc memory allocation).

I think its only the VDI that touches the blitter. The VDI in TOS 4.0x does not
include software support, unlike previous versions, however NVDI does 
- so simply
using this and de-selecting the Blitter option will disable blitter accesses
on the Falcon.

This is the recommended action to solve similar problems with FX-ram 
[no blitter
access]. Also included is a small program called ANMALLOC, which also 
solves the
problems for the FX [presumably causes desktop to malloc from ST 
ram?] for users
without NVDI.

> As the DMA & Blitter aren't PMMU-aware you cannot do DMA transfers from or to 
> paged memory and you can write to bad memory locations by simply moving your
> mouse !

I dont think DMA transfers are valid from TT ram either, so I dont think that
will cause problems for most apps.

> One way to solve this problems would have been to create a patch for the Falcon
> 4.02 and 4.04 Xbios to let us disable the Blitter, but I was to busy to do this
> and when I got some time, the new VM were released. I saw no needs to release
> mine. (I didn't know that it didn't work ok in all situations.)

Argh! if only you had said, we might have been able to help! oh well. 

ATB

Anthony
-- 
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Anthony Jacques           IRC: AnthonyJ | Bad Mood, GEM-DEU, FracTalk,
                          ICQ: 11287923 | STOS patching, Falcon Extn,
jacquesa@zetnet.co.uk                   | MiNT.CNF, Reschange, Tuna,
http://www.users.zetnet.co.uk/jacquesa/ | and more... which shall I do?
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