RAM vs FSB

[None of the above]

Gentlemen,

I'd be grateful for some assistance in working out whether it would be worthwhile replacing my PC RAM with higher speed cards.

I have a home made XP/Vista dual boot system with 4 x 1Gb of RAM. (Crucial 1GB DDR2 533MHz / PC2- 4200 Unbuffered Non ECC)
Since installing it I find that Vista is only capable of recognising 3.25Gb.
Well, we all make mistakes.

I am considering replacing the RAM with DDR 2 PC 2 6400 800Mhz cards.
Now, this is where I have some difficulty. (Apart from the little faux pas above). I do not understand the complex relationship between FSB speed and RAM speed. My Asus M2V mother board is described as having an FSB of 2000MT/s which I believe is more commonly expressed as 1000Mhz.
I understand that there is a point at which the memory works faster than the FSB, to put it in somewhat simplistic terms, and as such is 'wasted effort', so would 4 x DDR 2 PC 2 6400 800Mhz cards 'overtake' the FSB speed?

One more relevant(?) thing, the CPU Spec:
AMD Athlon 64 X2 4400+ (2.3 GHz) Socket AM2 Energy Efficient L2 1MB (2x512KB) cache.

Any assistance would be greatly appreciated.

Thanks

N o t a


PS: I can't remember how I decided on the spec when I built this machine, but I suspect that it came together more by good luck than good management.

[Saab Dastard]

Yes, even though 32-bit Vista says it supports up to 4GB RAM, there is only approximately 3.3GB of addressable memory, as Vista reserves upper memory space for hardware usage.

Ditto for 32-bit XP, although applications cannot access more than 2GB (see MS site for more details).

64-bit versions of Vista support at least 8GB, rising to 128GB for higher-end editions. 64-bit XP supports 128GB IIRC.

So don't replace your RAM, replace your OS! You have a 64-bit processor...

[E.Z. Flyer]

DMA > Direct Memory Access

http://en.wikipedia.org/wiki/Direct_memory_access

All systems can use the direct memory access channel. Although, I expect each system might be different in that the DMA is likely configured through the system BIOS. Or that, you'll see from within system properties the channel, and how it is addressed in relation to memory buffers and the like once you know the channel number. The link above explains the characteristics of DMA, and as such, RAM that exceeds the speed of the FSB is not always an issue. Although, it is a given that the most significant issue is whereby the CPU and FSB onboard must be set to the corrected overclock speed to work with the faster memory. In some instances the Hyper transport protocol may still yet need to be recognized varying upon the type of graphics card in use and how Vista handles such calls. FSB Overclock

Perhaps the next service pack for Vista, if not the one that was just released will serve to resolve the amount of memory Vista is able to initialize.

I wonder if Vista is only limited now by the introduction of such programming modules as Direct X? But, it should however, always recognize virtual memory paths and settings.

[None of the above]

Thank you, Gentlemen,

I must admit that it hadn't occurred to me to go for the 64 bit version of Vista, but that does sound to be worthy of serious consideration.

Thanks again, chaps.

N o t a

PS I've also built a dedicated Linux box which is going quite well on Ubuntu. The ultimate aim is to stop contributing to Uncle Bill's pension fund, but might be a little while yet.