BIOS detects 4 GB RAM, but kernel does not 1933

Understood -- I realize now (finally) if you compiled the kernel (for Debian) the place to grep would be most likely in major reasons behind 64bit-EM64T-x8664 (and even the 64bit instructions that are native only to Itaniums, which is not backwards compatible with 32bit) in the 1st place is to eliminate that 4GB RAM barrier ... so what gives ? Except: maybe perhaps as General S says: you'll need a newer kernel (above 2.6.15).

I understand you're running CentOS4.3 Final -- which is basically the free version of RHEL ..yes?

see why above (mostly)... That doesn't necessarily mean that some kind of certain 'config' doesn't need to be compiled into the kernel. Yet I'm not sure exactly which options are necessary, if any, nor am I sure you can achieve your goal using what *seems* (Robert Hanchicken's reponses) to be essentially an Intel DualCore 32bit CPU(s). I'm having a bit of trouble understanding (or believing) that an EM64T system isn't capable of seeing more than 4GB RAM (although the Mobo max for that Desktop mobo is 4GB) -- BUT then again, that is not a Server grade Mobo either -- it's a Desktop mobo (perhaps using an unsupporting(cheaper) Chipset(?). Yet; the BIOS detects all 4GB (which shoots down my chipset theory) - so maybe it's a kerenl specific issue (harkens back to General S's response about 2.6.15+ kernels only). In my earlier post, I hadn't realized you were using a 64bit kernel.

Since this *other* PC is running a 32bit kernel(?), try a 'newer-than-2.6.15' kernel on that machine. You should be able to achieve success by recompiling. Though if the Mobo doesn't support it (iomem mapping hole), you may be borked.. :( I'm not sure.

So basically you have a Intel Pentium D 8xx series Dual Core CPU (which model) on CentOS 4.3 Final, in a Intel Desktop D915GAV Mobo....

-- and another ("similar") PC with a *P4* (Pentium D == Dual Core) - diff Mobo I presume? s775 ? -- yet many of the 5xx, 6xx and EE series do indeed have EM64T capabilties....and all Pentium Ds (8xx series) should too -- even the 840EE edition. So when you say "only diff is it's 32bit instead of 64" - you must mean the Kernel-OS version.

That's to be expected, IF indeed the 2.6.17.1 kernel you tried was NOT a 64bit kernel -- but try that 2.6.17.1 kernel in the 32bit Intel p4 (PentiumD) machine...the one running a 32bit kernel.

Perhaps not...I'm not sure -- but maybe Robert and others are. Himself, and some others here, know much more about it than I do atm. I've gotten a bit rusty on my newer hardware knowledge, and am not as well following AMD64 tech more closely then anyways.

advert terminology

Peace ;)

Regards