Messages in this thread | | | Date | Fri, 14 Jul 2000 17:15:21 -0700 | From | "H. Peter Anvin" <> | Subject | Re: Comments wanted: Linux/i386 boot protocol doc |
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Alan Cox wrote: > > > | Reserved for BIOS | Do not use. Reserved for BIOS EBDA. > > 09A000 +------------------------+ > > 9A000 is not a guaranteed address. The EBDA is defined by reading a low memory > value
I know, and I address that in the document. Boot protocol 2.02 plus bzImage allows the boot loader the flexibility to set the memory ceiling quite low. However, we needed a "drop dead" address for existing kernels as well, and John, Hans and I came up with 0x9A000 as being something we can reasonably do. It is not always sufficient -- when using M-systems flash or PXE the EBDA is several hundred K in size. There is no way to support this with the old kernels which require mucking with the 0x90000 segment. Hence the revised protocol.
However, I'll see if I can add a note.
The problem is that most of these are hard limits for the boot loader -- doing INT 12h to find out the ceiling only allows you to print an error message instead of crashing.
-hpa
-- <hpa@transmeta.com> at work, <hpa@zytor.com> in private! "Unix gives you enough rope to shoot yourself in the foot." http://www.zytor.com/~hpa/puzzle.txt
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