RE: ARGH! Memory upgrade hades...

David,

I'm afraid that is a common issue not just with Sony Vaio.
Without getting to deep to the technical bits:
Current memory technology running very close to its physical limits. One of the limiting factor is capacitance load on high speed signals. 
So may be you just get unlucky and have the 512MB module too close to the spec limit. You may find another module (may be from a different vendor) does work OK but if your specific memory controller is close to its spec limit as well, you may not be able to find any two 512MB that work at all.
That is one of the reason why vendors specify less memory than the absolute limit of the controller.

Hope this help.
Jeno.

> Machine: Vaio PCG-GRV550
> OS: SuSE 8.2 (but not really relevant at the moment)
> 
> So I got two 512MB modules.  Either *one* of the modules in a slot by
> itself works fine.  But if I try both modules or one 512MB module and
> one of the old 256MB modules the PC never gets to displaying the "Sony"
> Logo.  
> 
> Apparently I am *hosed* for upgrading this machine to 1GB - regardless
> of what EmperorLinux or anyone else says... :-/