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memory areas
Posted: Thu Oct 31, 2002 6:43 pm
by neowert
what area are reserved by thr vpu and devices. I need to know what areas of memory I can use. I know the first 1K or so of memory is reserved for the IVT. I am fairly sure the video card uses some address space too. what else, or is there a standard way of knowing?
Re:memory areas
Posted: Thu Oct 31, 2002 6:44 pm
by neowert
er, vpu=cpu. thr=the. sorry
Re:memory areas
Posted: Thu Oct 31, 2002 6:45 pm
by neowert
er, vpu=cpu. thr=the. sorry
Re:memory areas
Posted: Fri Nov 01, 2002 6:31 am
by Tim
In general:
- The bottom 4KB are reserved for the interrupt vector table and the BIOS Data Area
- An area just below 640KB is reserved for an Extended BDA on some machines
- A0000-FFFFF is full of ROMs and memory-mapped devices; don't touch that unless you're e.g. accessing video memory
- PCI devices will put their memory areas higher up; you can ask PCI where these are. Note that these areas should be well away from physical memory (usually at the top of the 4GB physical address space)
Re:memory areas
Posted: Fri Nov 01, 2002 1:13 pm
by neowert
thanks
Re:memory areas
Posted: Tue Nov 05, 2002 11:07 pm
by Paul
Tim,
You said you can "ask" the PCI devices where their memory areas are......how?
Paul
Re:memory areas
Posted: Wed Nov 06, 2002 12:19 pm
by Tim
It's not trivial: you need to either call the PCI BIOS functions or access the hardware directly. OpenBLT, NewOS and Mobius all contain more-or-less the same PCI code, so download the source to one of these and copy it from there.