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Choosing ideal RAM speed for AMD Processor (3.2 GHz AM3 Athlon II 260)

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June 4, 2012 7:15:43 AM

Hi all,
I am looking to build a low end PC with AMD Processor(3.2 GHz AM3 Athlon II 260) and ASUS Motherboard(ASUS M5A78L-M LE). I was trying to study the relationship between CPU Multiplier, FSB and Memory Frequency in order to avoid potential bottlenecks that could happen on either Memory or the CPU end. When I had a resonable grasp over these three factors, I found that there is no explicit FSB for the AMD processor in question and that the Memory Controller is integrated inside the Processor.

Now I have two doubts.

If there is no FSB in the concerned AMD processor, then I believe there is not much left to discuss about the choice of motherboard as far as communication between the CPU and Memory is concerned (not very optimistic though).

Secondly, what RAM speed(frequency) should be ideal for the AMD processor in question. For Intel based processors, it is just a matter of calculating the bandwidth(data transfers per second) of the FSB and the Memory and generally strive to have a 1:1 ratio. But I am clueless about what to expect in case of AMD processor.

If someone can help me out with the above two issues, I would be very grateful.

regards,
Nirvan.
a b } Memory
June 4, 2012 7:49:17 AM

no clue what you're talking about with Intel. their memory controller is on the CPU too. the FSB is long since dead. And CPU multiplier never had anything to do with memory. Memory ratios determine the memory speed off the base clock(200MHz) and are automatically set. You'd never want to have memory running at 1:1

The Athlon IIs memory controller is 1333MHz. You can get it to run 1600 on most but it makes almost no performance difference and with a low end processor like that even 1066 would be fine.

If you really want to be paranoid check the recommended memory list for the board. but really any set of 1333 memory should work fine.
June 4, 2012 8:39:28 AM

unksol,

I can still see some dual core intel processors in my country's web markets listing FSB, so I thought that Dual Core processors produced by intel still use the FSB for communication with memory. I apologise for that.

With the ratio one-to-one(1:1) I meant that the amount of data sent by processor per second should be comfortably handled by the memory. For example if processor is sending out 5000 MB/s and the memory can handle only say 3000 MB/s, then there seems to be mis-match. Its like the CPU will have to wait for the memory. I have based this understanding on this article (http://onlythecons.com/fsb-system-cpu-and-memory-speeds...) and another one. This is the first time I am purchasing a non-branded PC, so I wanted to be sure.

I checked the memory list and you were absolutely correct. It does indeed list 1333 MHz memory in the recommended list of memory. But it also lists some high speed memory with (O.C) in brackets like this 1866(O.C), 1600(O.C)
I am not very sure what (O.C) means, but seems to be over-clocking.

Anyway, I think I will stick to 1333MHz RAM as per your suggestion.

Just one last doubt that I am not sure. The link above says the following in the end

Quote:
Most motherboard chipset memory controllers (that the CPU and RAM really interface through) has dual channel technology, meaning it can read/write to two (2) memory modules at once. Thus, 2 sticks of DDR-800MHz RAM has, effectively, 12,800MB/s of bandwidth (6400MB/s x 2)


Is that true that using 2 smaller capacity (say 1GB RAM) instead of a single 2GB can increase the memory bandwidth ?

Thanks very much for your help.

regards,
Nirvan.
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a b } Memory
June 4, 2012 9:28:27 AM
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The (O.C.) just means you will be running faster than the memory controller is rated (overclock) . The board can set that speed but you may have to.mess with timings/voltage manually to get it to work if it does at all. lot of hassle for almost no performance improvement. not a good idea if you're new to it.

The memory controller on AMD CPUs is dual channel.Youre quote is exactly correct. So by using 2 smaller chips(in the correct slots) and installing them together in a pair you get double the memory bandwidth with the same amount of memory.

However, motherboard integrated GPUs like on the board you listed take chunk of system memory (if you choose to use it) and used to force it into single channel mode anyway. I am not sure if that's the case with that AMD chipset or not
June 4, 2012 10:42:45 AM

unksol,

I won't be over-clocking the pc, as I know very little about it. Although, I know it in theory, I am still afraid of doing that just yet. I will close this question here. Thanks for your help.

Nirvan.
June 4, 2012 10:44:44 AM

Best answer selected by nirvanbd.
a c 146 } Memory
June 4, 2012 7:20:00 PM

This topic has been closed by Nikorr
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