The bug was that the 3C905B with the Lucent chipset and some early prototypes ofthe 3C905C didn't map contents of the ROM properly - the ROM was remapped to the shadow memory after every 4K, not 8K as is commonly thought. Even the ROM couldn't be properly read directly using ASIC I/O access to the ROM - it produced the same remapping problem. Forcing the ASIC into MII mode solved the problem, but it was required that one restored the ASIC to its original setup afterwards. The early revisions of 3C905C did have this bug too, that was what the loader patch was about. Later revisions of 3C905C do not have this bug - last summer we changed the patch - we now skip the workaround for 3C905C and continue to apply it for the 3C905B. Here is a brief summary of what has been done to the >4K loader problem in 3C905B with Lucent ASIC: As the first 2K of loader is remapped in UMB after 4K, it was suggested to checksum this 2K properly in order for the BIOS at least not to produce checksum error and recognize the ROM. Then replace last 2K with the proper code from PCI-mapped extended memory during the autoscan time. The idea of checksumming works well.The last 2K of 6K loader code was copied properly from extended memory using Int15 copy function and was executed properly in autoscan time. But the ROM was never shown in BBS boot order afterwards. We experimented a lot and found that Int15 is the reason. Even if you apply some dummy copy like copy 2 bytes to the location far away from our 4K target (using a Broadcom chipset which operates properly ) the ROM never showed up. Probably the transition to protected mode in Int15 affects subsequent BIOS execution. We applied IO-based copy using 3C905B registers and it works fine. The ROM is visible for the BBS BIOS and operates properly. When copying the last 2K of the loader the Lucent Hurricane has to be put in MII mode too, because even reading BiosROM using registers gives the wrong location of the chip when not put in MII mode. But that is performed during run time and doesn't affect permanent EEPROM settings =========================================================================== This Mail was sent to netboot mailing list by: Steve_Marfisi@3com.com To get help about this list, send a mail with 'help' as the only string in it's body to firstname.lastname@example.org. If you have problems with this list, send a mail to email@example.com.
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