On Fri, Oct 02, 2009 at 11:39:50PM +0200, Carl-Daniel Hailfinger wrote:
I'll bite, what's the advantage of doing coreboot + SeaBIOS vs. SeaBIOS alone? Forget about EFI for the moment, should be considering switching to coreboot + SeaBIOS for 0.12?
Advantages:
- Code coverage increase: SeaBIOS is used with coreboot on real
hardware, so the BIOS interface part of SeaBIOS gets a lot more testing than the Qemu hardware init part of SeaBIOS.
- coreboot supports real 440BX hardware besides Qemu, so the coreboot
init code is exercised more (and there is still a sizable number of such machines around (clusters), many of them running coreboot).
QEMU goal is to run popular OSes and OS usually don't care about low level chipset details. That's way QEMU's chipset emulation implements only bare minimum that is needed for OS to run: no need to initialize memory controller for instance. Coreboot goal, on the other hand, is to talk to real HW, so to use it on QEMU will require implementing chipset features that are not needed to accomplish QEMU goal. So for me real 440BX hardware support of coreboot is actually disadvantage. QEMU don't have real 440BX hardware and there is not point in having one. It is possible to implement 440BX-qemu support in coreboot of course if there are other advantages worth having.
- Only one ROM image needed. A coreboot ROM can pack the VGA BIOS into
the ROM image and SeaBIOS will automatically load it from there. Same for network card ROMs (with gPXE etc.).
- coreboot ROMs (including those with SeaBIOS and/or EFI and/or VGABIOS)
are archives and can be listed/edited with cbfstool if you want to know what's in there.
- coreboot ROMs use compression, so you can stuff more code (and PCI
option ROMs) into smaller ROMs.
- coreboot has pretty verbose hardware init messages (if you want that)
and can be totally silent as well. The messages end up in a log buffer which can be read by the OS (experimental feature, not available by default).
There are a lot more advantages, but I want to give other coreboot developers a chance to chime in. If you add EFI to the mix, the synergies increase.
Regards, Carl-Daniel
-- Gleb.