Re: Too big EBDA issue

[H. Peter Anvin]

Followup to:  <[e-mail]>
By author:    ASA <[e-mail]>
In newsgroup: linux.dev.kernel
> 
> Today I had to upgrade DiskOnChip BIOS extender and after that I could not
> boot linux anymore. After digging hard in problem I found that EBDA was
> enlarged to 33KB so remaining conventional memory was reduced to 607KB but
> normal booting proccess bzImage loading requires at least 608 KB. After
> checking on other systems with DiskOnChip I found their EBDA have sizes
> typically of 29-31 KB.
> 
> Yeah, it is very large EBDA (normal PC's I checked just have only 1 KB
> EBDA). It seems DickOnChip BIOS requires much space on irder to store own
> temporary data to implement their TrueFFS.
> 
> But I guess that there will be some other BIOS extensions that will require
> another EBDA space. As far as bzImage loading model requires space of 32 K
> between 576K (0x90000) and 608K (0x98000) but almost no other place I think
> there is necessity to extend boot protocol in order to relocate 16-bit mode
> loader closer to the lowest memory bound, not to the upper one.
> 

That was done way way long ago.  If your boot protocol is 2.02 or
later, you can locate it anywhere between 0x10000 and 0x90000.  This
applies to bzImages only; zImages are still screwed.

You need a modern enough bootloader that knows about this and uses it,
however.

	-hpa
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