physical memory limit?

[Andreas Tobler]

Hi Peter,

Andreas Tobler wrote:

> Peter Grehan wrote:
> 
>>> I remember back in 05 we had a similar issue when I tried
>>> 'buildworld' on a G4 alu book. Then you suggested to me
>>> to reduce hw.physmem to 512MB.
>>
>>  Indeed, and I'm certain those problems were fixed in r1.115
>> of mmu_oea.c where the secondary PTEG hash was corrected.
> 
> Ok, then I trust you :)

Hm, I just read the commit log:
---
Remove bogus increment of re-hashed PTEG index. This snuck in with r1.12 
of pmap.c, and is potentially the cause of hangs reported on machines 
with a small amount of memory. On machines with sufficient RAM, and 
without a lot of processes running, this situation would probably never 
occur.
---

Irritating issue is the part with 'hangs reported on machines with a 
small amount of memory'. I do not have small amount of ram, neither did 
I have hangs. I had 11 at that time. Now I have 11 again, but maybe due 
to other issues. Well on OS-X the machine does not complain. Even 
memtest doen't complain during the one hour period I let it run. Also, 
it might be that this needs a looong run of memtest to uncover something.

Anyway.

>>> I'll reduce/replace the memory and see how it behaves.
>>
>>  OK, let us know how it goes.
> 
> First step passed, I reduced to one 512MB DIMM and a full buildworld 
> with parallel qt build passed.
> I'll try overnight with the other DIMM to exclude single DIMM failures.
> But still, I have some more possibilities then, slot1/2 is defect, DIMM 
> 1 does not like co'op with DIMM 2, ECC vs. non ECC (one is marked with 
> ECC support, the other isn't).
> Will take some hours to find out.

Continued and found that both DIMM's seem to work in the first bank. 
Running a buildworld with a DIMM in the second bank failed for both, 
ECC/non ECC. So it seems it might be a problem with my HW. :(

I even bought a new, non ECC DIMM and I seem to have the same pattern.

Right now I try with 768MB (512MB/256MB ECC).

Let you know about findings.

Regards,
Andreas