Re: Kernel executation from ROM

From: Jeremy Jackson (
Date: Mon Feb 19 2001 - 17:26:11 EST

"Eric W. Biederman" wrote:

> No it forbids executing boot roms that way, by a standard pc bios.
> The system BIOS in a PC is normally on the ISA bus which is reached
> across via the PCI bus with a PCI->ISA bridge.

Son of a gun, I missed that... sure enough my PIIX4 docs beside me here
show a #BIOSCS pin on the southbridge... Can anybody clarify what
this restriction does and doesn't apply to ? The MindShare PCI Arch.
book where I got that info from doesn't elaborate that much.

> The thing is slow it really doesn't matter, all you need to do is
> enable caching on that area of the physical address space. You can't
> do this on the alpha currently but only because the alpha sucks that
> way. You can on practically everything else.
> As for ROM being slow on x86 you can enable the MTRR to speed things

Don't MTRR's just do write combining?

> up. Usually though ROMs are at least as expensive as RAM, so it is
> pointless.

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This archive was generated by hypermail 2b29 : Fri Feb 23 2001 - 21:00:20 EST