Eric W. Biederman wrote: >Christer Weinigel <[EMAIL PROTECTED]> writes: > >>Hi, >> >>I've been stuck at home with a cold during the week(end), so I've been >>fooling around a bit with a National Semiconductor SC2200 based >>system. It has taken me a couple of days to get the chipset setup and >>ram sizing working, but now it can boot a Linux kernel from flash. >> >>The PCI bus with two NatSemi DP8315 ethernet chips on it works, the >>built in IDE and USB controllers also work. The built in serial >>ports, ACCESS.bus controller, watchdog and RTC also work. I have not >>looked at graphics or sound at all and getting that working will >>probably be a lot of work. >> The NSC SCx200 and the GXM use Virtual Registers where they emulate hardware functionality for Audio, Graphics and Power Management. Firmware provides virtual devices in response to SMIs generated by specialized hardware.
Virtual registers are I/O locations accessed with 16-bit index/data operations. The Geode hardware traps the I/O accesses. The SMM software interprets the data values and either treats the data as parameters or performs some function. Virtual registers provide a uniform method for the BIOS to customize SMM parameters and features. The virtual registers are the means one VSM communicates with another VSM. This is the area that NSC is tight lipped about. Bari
