AMD Confusion...

  ste_bla 15:14 12 Jun 2004

Looking at AMD motherboards and i have worked out that the normal 64 bit athlons 754 DON'T use dual data bandwibth with ram and the new 939 ones do.

However i thought the XP Athlons did do the dual data bandwidth thing but how come you have 3dimm slots on mobos? how can you have dual data speed connection with 3 as dual means 2? It just confuses the hell out of me help

  MartinT-B 15:30 12 Jun 2004

You'll notice that the slots are usually coloured. 2 of one colour (usually 1&2) the other different (3).

You can get the DDR buy putting matching ram (2x256 for example) in 1&3 or 2&3

However, you could take the same 2x256 and put them in 1&2 and then add a matching 512 and put it in 3. They will then be used as 2x512.

When I say matching, I mean all the same type (PC 2700 for example), and I would go so far as to make sure they were the same brand too.

  thms 15:33 12 Jun 2004

Just as confused.

I have just installed a Asus A7N8X-E mobo with AMD 2800XP processor. This supports dual channel.

According to the manual to use dual channel you need to load memory in slots 1+3 or 2+3 or 1+2+3.

Quote from top of page. "The motherboard comes with four Double Data Rate (DDR) Dual inline Memory Module (DIMM) sockets." then it shows 3 slots. I have memory in 1+3 and it seems to work ok. Wouldn't say it,s any faster though.

  Stuartli 15:34 12 Jun 2004

I think you are confusing DDRAM and the word dual in conjunction with mobos - the three slots are used to increase the amount of RAM available, normally using DDRAM.

The operation of the RAM is not affected whether you use one, two or three slots.

Incidentally, for your information, here's a bit about AMD processors and the often queried reason why lower AMD CPU speeds match higher Intel versions:

click here

  ste_bla 15:49 12 Jun 2004

No I'm not confusing the two, Dual Data Ram (DDR) means the ram and accept data twice in a clock cycle unlike the previous sdram. Dual Data Bandwidth is what I'm on about and if you have a pair of matched ram modules then it doubles the bandwidth between ram slots and rest of system.

  ste_bla 15:59 12 Jun 2004

And a much simpler way to work it out is;


Amd increase number of insturctions where as intel incresed freq.

And AMD aint that much cheaper really as i personally find that a 2.8 p4 = 3200xp and they pretty much same price. And 64bit software? well by the time proper 64bit stuff comes out the current skt 754 well be out of production so thats not really worth it and the new 939 will be so expensive might as well get a 2.8 northwood and upgrade to a 939 in 2/3 years

  ste_bla 16:01 12 Jun 2004

oh just thought freq means ghz/mhz

  Arthur Scrimshaw 16:02 12 Jun 2004


I'm not sure what you mean when you state "The operation of the RAM is not affected whether you use one, two or three slots"

The use of the dual channel mobo feature doubles the memory bandwidth, so it is important if you are fitting two sticks of ram to get them in the right slots as thms states.

In that instance the operation of the RAM is affected, though you might not be aware of it's impact unless you are processing a lot of data.

  bremner 16:05 12 Jun 2004

Here is nVidia description of Dual Channel DDR click here

  Arthur Scrimshaw 16:08 12 Jun 2004


Thank you - I thought I'd read it somewhere. :-)

  ste_bla 16:11 12 Jun 2004

You were right, i downloaded a gigabyte mobo manual and it said if i want daul data to work im only allowed to put 2 lots of ram in..

cheers everyone

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