AMD system

[torpidnotion]

Hello, I'm getting a replacement mobo/processor/ram for my parents.


Athlon 64 LE 2.2ghz 1MB L2 Cache Socket AM2 45W processor

ASUS M2V-MX SE AM2 Micro ATX Motherboard

And the RAM i'm not quite sure about. According to the board's manual it supports DDR2 533/667/800.

Now, it's been a while since I've built a system.

The board's FSB specs say it's 800mhz (hyper transport)
The RAM is DDR2 800 (200mhz effective)
The processor is 2000mhz (hyper transport)

I'm confused at the relations here.
When I built computers in the past (its been a few years), everything was simple.
You had the FSB speed (like 100mhz) * multiplier = processor speed, and the RAM ran at the same speed as the FSB (like PC-100).

So what exactly is this system running at, and does this mean the RAM is the bottleneck here, being the CPU supports 2000mhz HT? Do I need DDR2 800 or can I go with 533 or 667?

 

[justly]

AMD now has an integrated memory controller (actually two) built into the CPU so memory is no longer accessed through a FSB.

What this means is there are now two links (or buses if that makes it easier to understand) directly to the CPU, one is used strictly for memory and the other (the Hyper Transport link) is what communicates with the other devices in a computer.

Unless you are planning to overclock there is no need to worry about the relation these links/buses have to each other.

For a basic home computer I don't know if there would even be a noticeable difference between DDR2 667 or 800. There really is no reason to go DDR2 533 since it's doubtful that you will save any money going with it and may even notice a performance drop in normal/every day use.

 

[torpidnotion]

Originally posted by: justly
AMD now has an integrated memory controller (actually two) built into the CPU so memory is no longer accessed through a FSB.

What this means is there are now two links (or buses if that makes it easier to understand) directly to the CPU, one is used strictly for memory and the other (the Hyper Transport link) is what communicates with the other devices in a computer.

Unless you are planning to overclock there is no need to worry about the relation these links/buses have to each other.

For a basic home computer I don't know if there would even be a noticeable difference between DDR2 667 or 800. There really is no reason to go DDR2 533 since it's doubtful that you will save any money going with it and may even notice a performance drop in normal/every day use.

That helps alot. Thanks!

 

[0roo0roo]

get 2 1gb sticks atleast
rams dirt cheap now
more ram is good.

 

[torpidnotion]

Originally posted by: justly
AMD now has an integrated memory controller (actually two) built into the CPU so memory is no longer accessed through a FSB.

What this means is there are now two links (or buses if that makes it easier to understand) directly to the CPU, one is used strictly for memory and the other (the Hyper Transport link) is what communicates with the other devices in a computer.

Unless you are planning to overclock there is no need to worry about the relation these links/buses have to each other.

For a basic home computer I don't know if there would even be a noticeable difference between DDR2 667 or 800. There really is no reason to go DDR2 533 since it's doubtful that you will save any money going with it and may even notice a performance drop in normal/every day use.

Oh and another thing -- are the buses independent as well on the current intel-based systems? I have a Core 2 duo 2.3ghz system, and I happened to already order DDR2 800 (the board supports 667/800/1066)?

I guess i'm still confused as to what the benefit is of having a faster memory bus speed is if there's really not a huge difference, and why it's needed to have the higher memory (1066) for overclocking (which I don't plan on doing BTW). I'm also open to web links that explains it. Thanks in advance.

 

[Aluvus]

Originally posted by: torpidnotion

Oh and another thing -- are the buses independent as well on the current intel-based systems? I have a Core 2 duo 2.3ghz system, and I happened to already order DDR2 800 (the board supports 667/800/1066)?

Intel still uses a traditional "quad pumped" FSB. If your processor has a listed FSB of 1066 MHz, that is driven by a 266 MHz clock; you would want to buy at least DDR2-533. For a 1333 MHz FSB, DDR2-667. Your memory will be fine.

I guess i'm still confused as to what the benefit is of having a faster memory bus speed is if there's really not a huge difference

It can be a pretty substantial difference, although how substantial varies wildly based on the particular CPU (Netburst processors benefited greatly from faster memory while Core processors make much "smarter" use of the bus, for example). There are a somewhat horrifying number of variables that go into memory performance, unfortunately.

For desktop users, the higher throughput of Hyper Transport is not that big a deal, as performance of K8 (and now K10) processors like the Athlon 64 is not as heavily influenced by memory as performance of, say, Netburst (Pentium 4 etc) processors was. However, because it is a point-to-point link (and not a shared bus) it scales better for multi-processor Opteron systems. That is where it shines.

and why it's needed to have the higher memory (1066) for overclocking (which I don't plan on doing BTW).

Memory that is rated higher can be clocked up to stay in synch with the FSB (for Intel CPUs) and just to keep up with the increased demands of a faster processor.

 

[justly]

Aluvus, thanks for answering torpidnotion's questions.

torpidnotion, sorry I wasn't able to get back to your questions any earlier, but if you still feel the need for more information just say so.

 

[torpidnotion]

Originally posted by: Aluvus

Intel still uses a traditional "quad pumped" FSB. If your processor has a listed FSB of 1066 MHz, that is driven by a 266 MHz clock; you would want to buy at least DDR2-533. For a 1333 MHz FSB, DDR2-667. Your memory will be fine.

Ahhh OK... Now is it just coincidence that the DDR2 requirements are half that of the FSB speed, or am I missing something here? Because I thought the memory speed was now independent of the FSB? Or is that just for hypertransport (AMD)?

 

[Aluvus]

Originally posted by: torpidnotion

Ahhh OK... Now is it just coincidence that the DDR2 requirements are half that of the FSB speed, or am I missing something here? Because I thought the memory speed was now independent of the FSB? Or is that just for hypertransport (AMD)?

Memory and FSB speeds can now be decoupled (this is "asynchronous" operation), so for instance it is possible to run the memory at a lower speed than would match the FSB. However, there is a performance penalty for doing this. It is also possible to run the memory faster, which can also cause a (milder) performance penalty.

The speeds come out to half the FSB speed because of the way they are determined. The FSB speed takes a clock speed (say 266 MHz) and then "quad-pumps" it (say to 4x 266, or 1066 MHz). The memory takes a clock speed (again say 266 MHz), and then doubles it (say to 533 MHz). So it's more than just coincidence.

Hyper Transport does some slightly more complex things, which honestly I'm too tired to explain adequately right now.

 

[musicetime101]

Corsair 2GB (2x1GB) PC2-6400 Dual Channel memory $25:
http://shop3.outpost.com/product/4960001

 

[Roguestar]

Originally posted by: torpidnotion

Originally posted by: Aluvus

Intel still uses a traditional "quad pumped" FSB. If your processor has a listed FSB of 1066 MHz, that is driven by a 266 MHz clock; you would want to buy at least DDR2-533. For a 1333 MHz FSB, DDR2-667. Your memory will be fine.

Ahhh OK... Now is it just coincidence that the DDR2 requirements are half that of the FSB speed, or am I missing something here? Because I thought the memory speed was now independent of the FSB? Or is that just for hypertransport (AMD)?

Nope, because the listed speed of DDR2 and of a 'quad-pumped' FSB are in that ratio because their 'actual' speeds are therefore the same. It is preferable for memory and CPU to run in this 1:1 ratio.