Messages in this thread | | | From | "Petr Vandrovec" <> | Date | Wed, 8 Jan 2003 21:49:39 +0100 | Subject | Re: PCI code: why need outb (0x01, 0xCFB); ? |
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On 8 Jan 03 at 10:52, H. Peter Anvin wrote: > > > 1. which device is at port address 0xCFB? > > Hopefully none.
Actually I'm not sure. This code is here since at least 2.0.28, and during googling I even found code for direct PCI access (http://www-user.tu-chemnitz.de/~heha/viewzip.cgi/hs_freeware/gerald.zip/DIRECTNT.CPP?auto=CPP) which sets lowest bit at 0xCFB to 1 before doing PCI config accesses and reset it back to original value afterward.
So I believe that there were some chipsets (probably in 486&PCI times) which did conf1/conf2 accesses depending on value of this bit. Unfortunately I was not able to confirm this - almost nobody provides northbridge datasheets from '94 era, even Intel does not provide them (f.e. Neptune) anymore :-( Best regards, Petr Vandrovec vandrove@vc.cvut.cz
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