Am Samstag, den 29.05.2010, 00:30 +0200 schrieb Michael Karcher (myself):
Motherboard: Shuttle AV11V30
... of the mainboard, or the BIOS code. Your flash chip has an optional boot block protection mode. If that mode is active, programming in the boot block and, this is what you observe, the chip erase instruction (which would also erase the boot block) is ignored by the flash chip. This also applies to the vendor flash tool, so please check that you don't have flashing disabled by a jumper or a setup option.
I just have seen that you did flash other flash chips successfully. Also the boot block protect mode will not be active after hot-swapping, because it is reset by power cycling. The behaviour you are observing is indeed interesting: We can be sure that write cycles reach the chip, as otherwise, probing would not have worked, but the chip does not respond to the erase command.
Also we have confirmed working erase on the original Winbond chip. So currently I am out of ideas why this chip does not erase.
Regards, Michael Karcher