Re: [parisc-linux] Linux only see 2Gb of ram of N4k

[Joel Soete <soete.joel@tiscali.be>]

Matthew Wilcox wrote:
> On Fri, Feb 20, 2004 at 07:04:26PM +0100, Joel Soete wrote:
> 
>>Hi all,
>>
>>My collegue make me notice that the N4k on which I can test Linux was supplied
>>with 4Gb of ram (which if confirm at boot prompt) but Linux only see 2Gb.
>>
>>It is a dual cpu machine, is that 1/2 ram dedicated to 1 cpu and the other
>>1/2 to the 2d cpu?
> 
> 
> Unlikely.  As I recall, the N4k diagram looks like this:
> 
> <-PCI-> Elroy <-Ropes\      PA <-+-> PA        PA <-+-> PA       /Ropes-> Elroy
> <-PCI-> Elroy <-Ropes-\         DEW       RAM      DEW          /-Ropes-> Elroy
> <-PCI-> Elroy <-Ropes--> IKE <-Merced-> Stretch <-Merced-> IKE <--Ropes-> Elroy
> <-PCI-> Elroy <-Ropes-/         DEW       RAM      DEW          \-Ropes-> Elroy
> <-PCI-> Elroy <-Ropes/      PA <-+-> PA        PA <-+-> PA       \Ropes-> Elroy
> 
> So the RAM is uniformly-accessible from all CPUs, but the IO is not.

That is also what I believe to have understood from our previous talk about N Stretch mmu
(but I am never sure to well undertand, thanks to confirm)

> 
> If you look at pat_memconfig() in arch/parisc/kernel/inventory.c, you'll
> see how we try to figure out what memory ranges are in the machine.
> Want to try debugging that, see what's being reported by firmware?
> 
I will try.

Many thanks,
	Joel