On Saturday, February 21, 1998 2:37 PM, Benjamin Scott [SMTP:hawk@ttlc.net] wrote:
Remember that the CMOS settings are stored in the NVRAM, not the flash. Now the question is how big is the NVRAM? I don't think we have room for this.
Why do these have to be stored in the NVRAM? Can't we reserve 1K or so of flash for this sort of thing? Or can't you erase and replace just a little bit of flash at a time?
All things considered, you really don't want to flash the BIOS too often,and especially not behind the users back, so to speak
NVRAM varies from machine to machine some of the chips now have several K available since a number of BIOS' store the ESCD (needed for PnP) info in NVRAM rather than flash. Most of the flash ROMs support up to 100,000 reprogramming cycles.
Flashing the BIOS often would be a Bad Thing. There is a limit to how often you can write flash ROM. It would take awhile to hit it, but it is a real limit. Plus, I think you need to erase flash ROM in banks of a certain size. At least, I've seen plenty of stuff that worked that way and that way only.
You do need to flash in blocks. The size of the block depends on the chip with the modern chips now having small blocks for storing configuration information, e.g. the Intel 28F001BX-T (128K)has two 4KByte parameter blocks plush a 8KB boot block. The boot block has extra HW protection to prevent accidental reprogramming. This is how the Intel boards prevent you from completely trashing your bios by mistake and ruining the motherboard (since the flash chips are not removable on Intel boards).
If we're going to store boot configuration info on disk, we might as well just go back to using LILO. I want something that can boot your selected OS without the need of loading from the disk.
So do Microsoft and Intel. This is why they've put together the NetPC spec, and why there is etherboot and netboot now available for Linux. You can burn/flash a ROM today that you can put in your ethernet card's ROM socket and do a net boot with out every touching your hard disk. Take a look at http://www.slug.au/etherboot.
Bill
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