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Could I disable a Xeon's second QPI?

post #1 of 9
Thread Starter 
Hi all. This might get a little long winded but please bear with me. I have an extremely technical question here.

OK so here is the deal. About a month ago I bought a Xeon engineering sample from Ebay USA (I reside in the UK). It's a hexa core Westmere EP CPU (1.8ghz 60w 0.9v).

I have an Alienware Aurora X58 board (MATX) running the latest bios. Now here is what happens when I boot it.

I press the power button. It starts, then shuts off. Then it automatically starts again, then shuts off. Then, on the third time I get this.

1-3.jpg

And then I can go into bios and poke around as normal.

2-3.jpg

But... As soon as I exit, no matter what changes I make in bios the machine will just sit on a black screen with no monitor activity.

After some research I have found out that the only difference between my CPU and say, a 980x (aside from voltage, power consumption, clock speeds etc) is that the Xeon has two QPI links. Then after more research I discovered that people were hard modding certain EVGA boards to disable the second QPI link

OK so here is my question. Is it possible to hard mod the CPU itself (maybe by shorting it somehow) to disable the second QPI link? my board will boot it as you can see, but I'm pretty sure that when it tries to actually boot normally the second QPI link is the culprit. Could I disable the second QPI link by hard modding the CPU? or could the board be modded?

Thanks for reading guys.

Jbod.
Edited by Jbod - 2/23/14 at 1:47am
post #2 of 9
Not sure about disabling a QPI Link, but have you updated the Bios to latest version?
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post #3 of 9
Thread Starter 
Quote:
Originally Posted by jasjeet View Post

Not sure about disabling a QPI Link, but have you updated the Bios to latest version?

I have yes.

OK, so I have been doing my research. Warning - this is for pure geeks only.

OK so I have found two tech docs on LGA 1366. Not only that, but I have worked out pretty much everything about the socket and what every single pin does. If you take a look at this picture you can see that Intel refer to each pin inside the socket (IE each location) as lands. Not pins, lands.



There we can see what lands the second DDR lane does (not DDR2 as in old DDR2, but the second DDR socket out of six).

Moving on we can see here where the QPI pins reside....



Now we can see that there are two QPI listings. One is DRX and the other is DTX

I now assume that because there are only two that each one is one of the two QPI links a Xeon carries. I also assume that Intel have hard coded the 980x to disable one of the QPI lanes. Now if we take a look at this picture here....



We can figure out exactly where each land sits. IE - what pins do what in the socket. I have a full directory of the lands in PDF form.

So, what I need to know is which of the two QPIs is the primary and which is the second one I need disabled. I could then (theoretically) block those lands from connecting with something like insulation tape (over the flat brass parts on the CPU) and then in theory disable the second QPI.

So let's take a board that has a single socket and does work with a Xeon. This is done simply by the bios telling the board to disable the second QPI lane. This has been done as a hard mod on EVGA boards by simply shorting one set of pins...
post #4 of 9
Thread Starter 
OK well hopefully some one here is techy and can help me on this.

OK. I went through the pin out diagram from the 980x tech manual and mapped out all of the QPI pins. I then mapped out the Xeon. So first up, here are all of the QPI pin outs from the 980x.

980xpinuse.jpg

And from the Westmere-EP Xeon 5000 series...

XEONPINUSE.jpg

Note the similar top pattern? OK so what I've done here is overlay the two pictures then blend them. Note - any green and red pins will turn dark green, any remaining empty pins from the 980x diagram will turn light green, as they are blending with white empty pins and not red ones.

combined.jpg

So, basically the Xeon uses EXACTLY the same pins as the 980x from the top of the socket. The only fathomable difference between the two is that the Xeon goes on to use the bottom of the socket for the second QPI..

So now my question is this. If I coat all of the bottom pins on the CPU preventing them from contacting will it then work in my board? or would it need a hard mod too?
post #5 of 9
Is this chip even supported by the board? Not all X58 boards support all 1366 chips. I have never heard of anyone physically modifying a CPU for any reason aside from cooling related.
 
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post #6 of 9
Thread Starter 
Quote:
Originally Posted by Prophet4NO1 View Post

Is this chip even supported by the board? Not all X58 boards support all 1366 chips. I have never heard of anyone physically modifying a CPU for any reason aside from cooling related.

First up. The 980x is a Westmere-EP with the second QPI disabled, as well as ECC support (I think, don't quote me on that one !). Thus, the answer to your question is two fold.

Does my board support a hex core CPU using the Westmere 32nm architecture? yes, it does.
Does my board support a Q3NW engineering sample? no.

My board does boot with the CPU in and goes to bios but only does so until you save and exit. Then it refuses to post. I'm not sure why that is, but, I would run a guess that the second QPI link is doing something? I don't know the answer to these questions obviously, that's why I posted this thread lol.

My board is out of an Alienware Aurora. It is made by MSI for Alienware, and, is very similar to their own X58M which is listed to support a W hex core Xeon. FYI - the only difference between a W and an E is that the W is single QPI. It's hex cored, 32nm Westmere.

As for modding to get Xeons running? there have been multiple instances of this. These days (with Sandy and on) board manus all include support for Xeons as there's really no reason not to. They are simply Sandy/Ivy/Haswell CPUs very similar to their desktop counterparts.

However, there has been a EVGA X58 mod to disable the second QPI (by shorting two solder points) and there has been a 775 mod to run 771 Xeons.

What I need to do is disable the second QPI link. Whether or not just covering up those pins on the CPU would work? I don't know. I don't know if you actually need to disable it on the board. That's why I'm here asking these questions. Sadly it seems there is no one around who is techy enough to be able to offer an insight into this. Shame frown.gif
post #7 of 9
My point was it would be easier to just plop in q chip the BIOS will recognize rather than fiddle with this setup. Even with the second QPI disabled the board may not talk to the chip. It might work, but you are dealing with an area very few bother to mess with. You might have to experiment on your own and tell us what happens.
 
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post #8 of 9
I think your main problem first is that xeon chip is an engeneering sample and is not supported fully by your mobo, In my rig i have a xeon x5680 with an asus p6td deluxe mobo, when i bought this cpu i had an intel dx58so motherboard with the latest bios at that time but the motherboard never ever boot with the xeon, so i bought p6td from ebay.
I'm writing thiw because i believe r problem isn't r xeon's second QPI but incompatibillity with r mobo, my intel board didt't post beep or anything , just the fans where spinning.
You can buy a second hand mobo to test but 1st 1366 mobos are stil expensive 2nd due to r xeon is an engineering sample nobady guarantees that even if r system boots that it will be stable in all occasions anf giving randomly bsods

p.s. Sorry for my english it;s not my 1st language
post #9 of 9
Sorry to revive a very old thread. But I couldn't resis.. @jbod could you continue your research? Pretty interesting none the less. I am quite disappointed that none are interested in this kind of enthusiasm even in this forum!!!!!!!!
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