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Volt-mod to make memory stable? No option to boost in BIOS.

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November 4, 2009 2:37:57 PM

Hey everyone, I have an old version of the Intel d875pbz board. It doesn't have the option to boost memory voltage in the BIOS. It is static at 2.5v

I've had 2 Geil ultra 400 512's (dual channel) running in there for 6 years with no problems. I recently installed an additional 2 256Mb versions of the same model. They are rated at 2-6-3-3 for 2.55v to 2.95v. Which leaves me 0.05 below the recommended voltage.

I ran memtest86 for 6 and a half hours and got 2 errors on test 5. From my research, this seems to indicate a voltage/timing issue. This wasn't an issue until I installed the two new smaller modules, so I think my motherboard is having trouble supplying enough voltage with 4 sticks installed. EDIT: The two errors occured on the 0 and the 3 DIMM slots

(I've also installed a new power hungry graphics card, but I don't think that would cause trouble when running memtest from a bootable floppy)

So my question is, could anybody help me do a volt-mod to my board? I think just a .05 to .1v increase would be enough to make these work fine.

I have no idea where I would draw with the pencil or place a resistor.

Here are links to a schematic and a picture of my board.

ftp://download.intel.com/design/chipsets/schematics/252... (I had to "save link as" with this pdf)
http://www.thg.ru/mainboard/20030714/images/intel_board...

I just moved the sticks to different channels, hoping that will fix things, and will run memtest again while I'm at work tonight. If that doesn't work, I hope I can do a volt mod so I can keep the factory timings. EDIT: Ran a short memtest repeating test 5, got errors on slots 0 and 3 again.

Any help or suggestions would be appreciated.
a b V Motherboard
November 4, 2009 2:57:34 PM

AFAIK there are no mods to increase RAM voltage.
November 4, 2009 4:00:08 PM

There are many posts on the internet explaining how to do it on various motherboards, just not this one.

Also, I edited my original post to show that I'm still getting the errors after switching channels.
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November 5, 2009 1:21:28 PM

Ok, I changed my timings to 2.5--7-4-4, ran test 5 repeatedly for 7 hours, and got 0 errors. This is definitely a voltage issue.

So I'd really like to get the super fast factory timings on these, and all I need is a ~.05V boost.

Could anybody tell me if this is the chip I need to v-mod? If so, which pins should I connect with a pencil? This is from page 76 on the schematic.

November 5, 2009 3:20:49 PM

After looking at some graphics volt mod faq's, evidently I need to connect the fb and gnd. I'll use a pencil and draw lines till I get something between 2.55 and 2.6.

Is there anything I'm leaving out here?
November 13, 2009 4:00:38 PM

Well, I ended up shading in the first resistor connected to the FB. According to most faq's this is the one to shade. The voltage reading on my RAM went up .05v.

I ran memtest #5 last night on the factory timings (2-3-3-6) and got 0 errors in over 200 tests!

I guess raising memory voltage has the potential to wear on the mobo, but this was a really small increase, so I think I'm in the clear.

!