What is all the ram used for?

[Mads Bondo Dydensborg]

On Wed, 31 May 2000, Doug Ledford wrote:


> > Upon inspecting the non-prefetchable memory, it seems that there are 16 MB
> > of it. (Writing 0xFFFFFFFF to it, reading back, 24 lower bits are blank).
> > However, the aic7xxx driver never seems to ioremap more then 256 bytes of
> > it.
> > 
> > Why is that? Is this memory somehow utilized elsewhere, or?
> > 
> > Any clarification would be greatly appreciated.
> 
> Your testing methodology is in error.  There isn't any more than 256 bytes
> worth of registers on the card, and anything you might be seeing with your
> test is the result of something else entirely.  The card doesn't even allow
> 32bit writes to portions of its register space, so you are certain to be
> confusing the card when you run this test and that is likely to produce odd
> results as well.

Hmm. 

My only excuse is that the test is from the Mindshare Inc book: "PCI
System Architecture", page 350, and they state that the procedure for
finding the size of a base address register is like I sketched out
above. They even give 2 examples. Part of the register being read only is
consistent with the method AFAICT.

Well, at least I now know that it is only 256 bytes. 

Thanks,

Mads

-- 
Mads Bondo Dydensborg.                               madsdyd at challenge.dk
Today, the record companies are saying MP3s are the biggest evil. Tomorrow 
they're going to say they're the greatest thing when they figure
them out.
                               - Gene Kan, Gnutella developer



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