K8N Neo4 Platinum nForce4 Ultra and 4 GB SDRAM DDR 400 Problem

Question

I have the K8N Neo4 Platinum nForce4 Ultra and 4 1GB sticks of Corsair ValueSelect DDR 400 (PC 3200), model VS1GB400C3, filling all four slots. The BIOS recognizes about 2.88 GB of total memory. The MSI manual states:
Quote
Due to the South Bridge resource deployment, the system density
will only be detected up to 3+GB (not full 4GB) when each
DIMM is installed with an 1GB memory module.
I'm not sure what this means. Does it mean that I'm "wasting" my SDRAM, that not all of it is used, or does it mean that all of it will be used and the BIOS just reports a smaller number?

Answer 1

Hi.
You seems not familiar with X86....
As you should know, Windows XP and most OS are 32 bits. That mean that every memory pointer is 32 bits, thus allowing to address 4Gb of memory.
BUT
In most OS, there is a difference between the kernel and the user. So, in most OS, the memory is divided in two 2Gb block (no matter how many Gb of Ram you really have!). The first one is for the OS, the 2nd for the user program.
So, If you have for example 3Gb of ram, in the best case, you have 1gb for system and 2Gb for user program.
To allow more Ram to fonction, PAE (Physical Address Extension) was made. Instead of 32, you got 36 bits for you pointers.
But as X86-32 CPUs can't handle more than 32 bits, a reserved area was made within 4Gb to allow Memory to be copied from the area the program want to read.
Exemple:
You got a server with 8Gb of ram. In windows, you only see 3.5+512Mb PAE.
If a program need to address memory in the 7-7.5 Range for example, the chipset copy the data from the 7-7.5 range to the 3.5-4 range in order to allow the CPU to get access: that's VERY slow.
So, in short: You can't have and don't need 4Gb of ram on 32bits OS.
(And there's even more place occupied by every card (AGP, PCI, PCI-e)....)
That's why XP64 is so interresting for programmers who needs lots of ram (Database....). When used with a chipset who know how to deal with lots of ram (I don't know if NForce4 can do it but I doubt it), you can load in memory a 4Gb Database.
But In all case, the bios should say 3.5Gb, not 2 and so on. You must have a problem with one of your stick. My guess is that they are all double sided and that you should slow down the memory to 333MHz.
(Or better: Send back 2x1Gb stick and get 2x512 SINGLE SIDED stick, unless you REALLY NEED 1.5Gb for your system !)