Date: Tue, 18 Nov 1997 04:37:53 -0600 From: Tony Overfield <tony@dell.com> To: Terry Lambert <tlambert@primenet.com> Cc: hackers@FreeBSD.ORG Subject: Re: >64MB Message-ID: <3.0.3.32.19971118043753.0071582c@bugs.us.dell.com> In-Reply-To: <199711101908.MAA11282@usr05.primenet.com> References: <3.0.3.32.19971110034509.0069e370@bugs.us.dell.com>
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At 07:08 PM 11/10/97 +0000, Terry Lambert wrote: >> If you can't trust the BIOS after the kernel is in memory, how can you >> trust it to load the kernel into memory? While the kernel is still >> "booting...", the BIOS should be safe enough to call in real-mode. > >Three problems: > >1) You can't trust a *user process* to call the BIOS (it's not > the sword that's the problem, it's what the peasent *does* > with the sword that makes us make them illegal for everyone > but the knights and the king). I didn't realize the bootloader had user processes. >2) The BIOS INT 13 code has a 2G limit on partition size, unless > you can guarantee all the devices in your machine support > LBA mode (even then the limit on LBA is lower than the limit > in FreeBSD... 64bits >> 32 bits). This appears to be completely wrong. First, I'm talking about bootloaders. I assume you agree that the bootloader should use INT 13. Second, the INT 13 interface (without LBA mode) is limited to 8.4 GB, not 2 GB. Third, the limit for LBA INT 13 is 64-bits worth of sectors, or 2^73 bytes. This should last us for several more years. >3) Gate A20 (now you will argue that Dell hardware doesn't use > BIOS code that expects a wrap in memory). Of course I will! I doubt any BIOS has ever been made that needs it. You'll no doubt cite some heap-o-crud(tm), obsolete system made by some long defunct company, probably with some ironic name like "Leading Edge" or something.... ;-) - Tony, who disclaims any proprietary interest in the marks and names of others.
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