Messages in this thread | | | Date | Sun, 19 Apr 2009 20:08:52 -0600 | From | Robert Hancock <> | Subject | Re: arch/x86/Kconfig selects invalid HAVE_READQ, HAVE_WRITEQ vars |
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Roland Dreier wrote: > > Also, atomicity might not be possible to guarantee on the bus level: > > say the device sits on a 32-bit PCI bus. (No matter what instruction > > the CPU gets, a readq/writeq there has to be done as two 32-bit bus > > accesses.) > > Well, the conventional PCI devices I know of with 64-bit registers were > PCI-X cards, keyed so they would only fit into a 64-bit slot. And of > course there is no such thing as 32-bit PCI Express.
It's quite possible to use most 64-bit PCI-X cards in a 32-bit slot, with the 64-bit part of the card not plugged into anything. It's supposed to work (as long as the card can handle the voltage the slot uses).
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