2.6.11 kernel can't see 4GB?

[Koen Tavernier <koen@ipec.co.uk>]

Hi,

I've been running a dual opteron box with 2GB for a few days. Today I 
added 2GB to the box, all recognised by the motherboard, but after 
booting into linux (with the stock 2.6.11 debian kernel) free only 
reports 3344996 Kb. I thought the 64 bit kernel avoided all problems 
with having lots of memory? Or should I pass the kernel a parameter?

I had a quick search through the list but couldn't see anything relevant.

Thanks a lot,

Koen.