Re: [Lse-tech] Re: maximum possible memory limit ..

[Andi K. <ak...@su...>]

> Cool. Sorry to be pestering about the 64-bit limits, but can we really
> use 2^64 bytes of memory on ia64/ppc64/x86-64 etc.? (AFAIK, 64-bit
> arches don't suffer from a small ZONE_LOWMEM.)

No. The hardware have far smaller physical limits. 

Current AMD64 CPUs are limited to 40bit physical, 48bit virtal
(the virtual limit per process in the current Linux kernel is 39bits) 

Itanium 2 afaik support a bit more 50bits (51 or 52, I forgot) physical,
probably more virtual.

Other 64bit architectures are somewhere inbetween.

The actual limit in the machines is even less. You will have a hard 
time to find an affordable machine (64bit or not) with more than 8 DIMM 
slots. That's 16GB Max with 2GB DIMMs.

-Andi