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Re: Debian problem on UltraSparc

On Fri, Dec 15, 2000 at 03:09:34PM -0500, Ben Collins wrote:
> On Fri, Dec 15, 2000 at 02:33:57AM -0800, Joshua Uziel wrote:
> > * Tommy Wu <newsletter@teatime.com.tw> [001215 00:56]:
> > >   1. I've 1024MB RAM on my box. But when I use kernel 2.2.18, it won't
> > >      boot correctly except I add a append="mem=512m" to let kernel use
> > >      only 512MB. Is there any configuration that I miss ? (I've try
> > >      2.4.0-test9 to test12, they will use all 1024MB RAM correctly)
> > 
> > This is expected and known... your only options are to use only 512MB of
> > RAM with 2.2.x or to have all 1024MB with 2.4.0-testX kernel.
> That's strange. We have an Ultra60 with 1.5 gigs running under 2.2.17-pre20
> with no problems. Why the difference?

Different PCI chipset. You basically have either PSYCHO, which has 32K
entries in IOMMU TSB, or SABRA, which has either 8K, 16K or 32K (depending
on which box this is). You can either set 8K or 64K granularity in this
translation table. 2.2.x uses 64K and sets 1:1 mapping of all memory in this
table, which means you can have at most 2GB (resp. 1GB resp. .5GB) of OS
usable memory. 2.4.x does dynamic DMA mapping (so this is history).


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