theory....

[i found nemo]

okay here we go


754 single channel

939 dual channel

now 184 pins in a ram stick

185 pins diff between the two...so i'm wondering does the 939 physically connect to the ram...in dual channel, and same thing with the 940??? is the extra 2/1 pin just a ground or extra + wire....

[i found nemo]

oops , mod could you move this to amd do'h

[TekXoID]

You're right. It's highly likely, but I'm sure the RAM's 184 pins go through quite a bit of
circuitry that differs between each sockets before it reaches the memory controller.

[STEvil]

thats exactly how it works actually.

940's have more than 1 pin re-ordered though, so the sockets are not physically compatable as far as I can tell.

I havent looked at all of the pins to be sure, though. If the ones in the way are just ground (VSS) pins then it'd be as easy as removing them and plopping the opteron into the 939 board. About 9 pins to check though.

[cadaveca]

dualchannel is a second stream of data sent along the same interface at a pre0determined delay. the extra pins give the memory controller the extra interface to the ddr. Pretty sure that's all ther is to it, besdies maybe some switching transistors to change the path.

[i found nemo]

about time one of my theory's was plausible

[FireDragon]

So then like the OPB i think it was FX55 that had 11 pins missing? so in other words if you could pull pins or "JUMP" them from the back of the mobo you can make an opteron work on a 939 someone NEEDS to try this...once I get some cash I will buy an El chepo 939 board and a the slowest opteron I can find...and give it a go

Dragon

[cadaveca]

the xtra pin from 940 to 939 was ECC/reg mem interface, i thought

[i found nemo]

yea i think ur right cadaveca

[STEvil]

the xtra pin from 940 to 939 was ECC/reg mem interface, i thought

if you look in the PDF's you will see that the extra pin is just for a pull down signal. The 939 processors have this pulled down by default where the 940's can have this on or off depending on the board.. thats why you can get 2-way opteron boards that dont require special ram..

PDF's:
http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/31411.pdf
http://www.amd.com/us-en/assets/content_type/white_papers_and_tech_docs/31412.pdf

However there are about 8 other pins on the bottom of the 939 and 940 CPU's which are not aligned to the same locations to make the sockets physically incompatable... you know those 4 solid spots you can see towards the center of the sockets on a 939 and 940 boards? They arent in the same locations.. so you'll have to rewire ~8 pins at least.

[i found nemo]

screw it, just drill a shallow hole...how about that, i bet it'll still work
...maybe

[STEvil]

if theres nothing under the plastic that'd be the way to do it.

[Absolute_0]

congratz on the theory that turned out to be correct, i found nemo

[$a1Ty]

what would be the point of running an opteron in a 939 board, doesnt make any sense :confused:

[STEvil]

cheap 1mb L2 chips, possibly top of the line mem controllers, possibly cheaper "X2's"...

[cirthix]

it woudl be more interesting to try s939 chips in s940

[i found nemo]

it'd be more interesting, to try both....939 in 940 and 940 in 939 IN THE SAME DAY yay