You have a custom embedded board, if I remember correctly? So you chose to make it "correctly".
Some PC motherboards, in an effort to deter BIOS viri, the ones that erase your flash bios leaving you with a brick if you open the wrong email, have connected the WE# line of the flash chip to SMEMW#, on the XT bus, so the chip doesn't respond to writes at 16MB (which is what the PIIX puts on the ISA bus when it gets a PCI access from 4G), only at 1M-64k. Then they program the north bridge for shadowing, and disable the writes to that window too. Of course a clever virus writer could just reprogram it... you need a jumper to totally defeat this type of attack. I like the idea of using the high alias only, but I do want to support these boards too. Maybe a config option, or each board-specific ipl.S can do whatever is best. Jeremy ----- Original Message ----- From: "Eric Seppanen" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Wednesday, April 03, 2002 1:46 PM Subject: Re: far call discussion > On Wed, Apr 03, 2002 at 01:14:01PM -0800, Jeremy Jackson wrote: > > Ideally both should be supportable, since some motherboards > > (my 430TX and 430FX) do not allow writes to the 4G > > alias, only the E-F segment. DoC needs that even to boot, > > of course. > > What? My 430TX board can write to the top of physical space; that's the > only way I ever access flash. >
