_IO_IS_ISA question

linas at austin.ibm.com linas at austin.ibm.com
Fri Mar 26 10:08:16 EST 2004

On Fri, Mar 26, 2004 at 09:28:17AM +1100, Benjamin Herrenschmidt wrote:
> That long ? Even when re-fetching from a hot cache line ?

If its out of cache, it would have been fast, but I had the impression
that it didn't pull from there. I dunno.  Don't let me add to the confusion.

> Also, think how long the actual IO is ...

In ye olden days, we used to build devices with blisteringly fast PIO.
Not only were we often faster than DMA, but so fast that the bottleneck
was in software, not the bus.  But that's a whole nuther thing.


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