On 10/28/09, Carl-Daniel Hailfinger <[email protected]> wrote: > On 27.10.2009 14:06, Darmawan Salihun wrote: >> What is the BIOS RAM in AMD SB7XX used for? >> >> Is it to buffer the BIOS contents from SPI flash chip prior to >> execution of the very first instruction? >> > > No. > > >> I recall that it's impossible to execute code directly in an SPI chip. >> > > Yes, but the chipset takes care of the SPI command interface and > presents the contents of the SPI chip nicely memory mapped to the CPU, > so the CPU can execute the ROM contents directly. >
I see. So, there must be some sort of independent microcontroller/microprocessor in the southbridge that "fetches" the contents of the SPI chip and "present" it in a "memory-mapped way" to the CPU. Probably this is how the BIOS RAM is used by the internal microcontroller/microprocessor in the southbridge. I suspect this because an ex-intel engineer that I spoke to, told me that back then he was using ARM7TDMI to do the job of "presenting the BIOS contents in a memory-mapped way" to the CPU. These days, the function must've been integrated in the southbridge as you said. I suspect AMD do the same. Regards, Darmawan Salihun -------------------------------------------------------------------- -= Human knowledge belongs to the world =- -- coreboot mailing list: [email protected] http://www.coreboot.org/mailman/listinfo/coreboot
