OEM's and CMOS Settings?

jolly good asks: "Back in the good old days all CMOS were accessed exactly the same way because there was an agreed upon standard in place. These days, however, motherboard feature sets have expanded to the point where the old 128 byte CMOS standard is no longer adequate. This has lead to different proprietary methods to access the upper 128 bytes in CMOS as there isn't a standard for a 256 byte CMOS. What I'd like to know is how are OEM's handling duplicating CMOS settings across large numbers of machines on production lines?"

Comments

What a totally obscure question

[LSD-OBS]

In the old days with 128-byte CMOS's, there were settings and bytes that weren't standard across different makes and models of motherboards anyway. I don't see what this has to do with recent boards requiring more CMOS settings/memory whatever.

And most people just use the default CMOS settings anyway, apart from maybe configuring the hard drives.

I really don't get this question.

Grab some datasheets

[tzanger]

The answer lies in the datasheets. Many RTC chips have more than 128 bytes of NVRAM, and use a bank swapping technique to select the alternate banks. Dallas Semiconductor is one such source, although most new systems have the RTC embedded in one of the main ICs of the chipset or on the super IO chip. Here is one example, the SMC FDC37N958FR, which is used in the Dauphin Orasis v1, an SBC I am experimenting with putting LinuxBIOS on to get around certain limitations. Page 215 is the start of the RTC/NVRAM access. This particular device has 256 bytes of NVRAM, several of which are reserved for the RTC and 8051 scratchpad. Since there is only 256 bytes, there is no bank switching. The DS1251 is an RTC/NVRAM chip with 512KB of static RAM. The little bitch is expensive, too. :-) It uses a banking method where one of the normally user-available registers is now a bank selection register.

I seriously doubt many systems have more than 256 bytes of NVRAM. That is a LOT of space for settings.