Messages in this thread | | | From | (Linus Torvalds) | Subject | Re: [PATCH] Cleanup port 0x80 use (was: Re: IO delay ...) | Date | Fri, 15 Mar 2002 21:33:45 +0000 (UTC) |
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In article <a6tm95$c55$1@cesium.transmeta.com>, H. Peter Anvin <hpa@zytor.com> wrote: > >The ISA bus doesn't time out; a cycle on the ISA bus just happens, and >the fact that noone is there to listen doesn't seem to matter.
The ISA bus doesn't time out, but the PCI access before it gets forwarded to the ISA bus _does_, if the ISA bus is decoded using nagative decoding.
This is why it's important that there not be a motherboard PCI device that can decode the port - because if there is, the access is potentially a much faster PCI-only decode.
Note that this really only matters on low-end machines anyway, as the whole "inb_p()" thing tends to be used only for old ISA devices. If you have a new machine that is all PCI, I doubt that port 80h access matters not at all.
(Another way of saying it: if you have a machine with a PCI POST card, none of this will matter)
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