Opteron memory Questions Here is

[MrMMills]

Opteron memory Questions

Here is my initial question:
PC2100 - DDR266 MHz (133x2) Opteron Supported
PC2700 - DDR333 MHz (166x2) Opteron Supported
PC3000 - DDR366 MHz (183x2) not Opteron Supported?
PC3200 - DDR400 MHz (200x2) not Opteron Supported?
PC3500 - DDR433 MHz (216x2) not Opteron Supported?

It looks like the memory on an Opteron board is accessed completely differently than traditional XP and MP based boards. From what I can tell the Opteron boards are geared to memory only as high as 333MHz. At least that is all the AMD docs (that I have read) have shown(for synchronous mode). See

http://www.amd.com/us-en/assets/content_type/DownloadableAssets/Opteron_Press_Preso2.pdf

The Opteron CPU has an IMC, (Integrated Memory Controller). What does this mean? – AMD says the following on page 13 of

http://www.amd.com/us-en/assets/content_type/

DownloadableAssets/Opteron_Press_Preso2.pdf

“The integration of memory controller functionality into the processor is designed to reduce DRAM latency, and scale memory bandwidth and capacity as the number of CPUs increases – improve performance on compute intensive server applications. Dual channel DDR memory interface on the AMD Opteron processor can increase memory throughput for increased performance. Full ECC and Chip kill can enable increased system reliability, helping to ensure your systems runs smoothly and flawlessly.”

Here are my remaining questions:
1) Is Opteron’s higher amount of onboard cache used by the IMC to buffer the data transfers to/from DDR memory?

2) Is there a “synchronous mode” and “asynchronous mode” in the bios (of Opteron boards) for memory speeds up to 333MHz? or over 333MHz?

3) Will it take an entire CPU revision for the Opteron to handle DDR memory faster than 333MHz?

4) Does the FSB still play into the performance of the memory?

If I remember correctly the ASUS A7N8X board actually ran better in synchronous mode with 333MHz DDR than with 400MHz DDR in async mode. I'm curious and would like to find out how the roadmap for Opteron boards allows them to better utilize the faster DDR memory types, assuming the CPU can handle faster memory accesses( with or without a CPU revision).

mrmmmills@onebox.com

 

[MrMMills]

Interesting note -
The Opteron has a 128bit 333MHz pipe while previous boards like the Tyan 2462 and 2469 had a 72 bit 266MHz pipe .

This means you get 45% more lanes of data highway going 20% faster (than a 72 bit 266MHz pipe). a difference of 5083 MB/s as opposed to 2283 MB/s

 

[rockerfellerz]

This proccessor is reviewed rather extensively at

http://www.anandtech.com/

Check it out...
I think it says that it will use only registered memory and it needs to be in pairs...but read for yourself.

If you're going through Hell...keep going... (Winston Churchill)
RocKeRFelLerZ

 

[MrMMills]

One other post I received stated the following info:

"technically the [opteron]processor is limited to ddr2700, and a revision will be needed for top of the line performance. The disabling feature is a temparary workaround in the meantime to try and keep up with performance increases."

Evidently there is a way to bypass the IMMC so that you can implement faster DDR memory but you take a performance hit to do so - I imagine the performance hit increases depending on the number of processors you are running per motherboard.

On another note-

Opteron has available memory bandwidth up to 5.3 GB/s (with PC2700)per processor while Intel Xeon's only have a cumulative of 4.3GB/s (see below)

AMD Opteron

http://www.amd.com/us-en/Processors/ProductInformation/0,,30_118_8796_8805,00.html

Intel Xeon

http://www.intel.com/products/server/processors/server/xeon/index.htm?iid=ipp_srvr_proc+xeon512kb&