Bought overclocked computer on eBay, but it's unstable.

[spencerb]

[This has been SOLVED Thank you]

Hello all,

I bought the following computer from eBay [Link removed now: But system specs are still listed below]

As you can see, it is advertised as "stable" at 3.1Ghz, however when I got it home it crashed during the first 3 minutes of a game. I tried many different games and it was always crashing within seconds or minutes of gaming. Far from stable! I suspected the system was not stable because of the overclock. I went into the BIOS and saw an option to save the current settings, so I saved the settings as they were so that I could load them again later if need be, and then I chose the option to reset to default safe settings.

Since then, under the stock settings (no overclock at all), the computer is fine playing intensive games for hours, and passed some of the stuff like Memtest that I made it do, so that's how I know the overclocking was to blame for the instability.

The stock system spec is:

Intel Q9400 @ 2.66Ghz, 1333Mhz FSB
8Gb (4 x 2Gb) Corsair PC2-6400 800Mhz Ram
Arctic Cooling Freezer Extreme CPU Cooler
MSI-P7N-SLI-FI Motherboard ("Supports up to 1333Mhz FSB")
2x Zotac GTX 260's in SLI
700W OCZ Modxstream Pro PSU
Three hard drives
Antec 900 Case, with loads and loads of fans...

I reset the BIOS to defaults and then had a go at overclocking it myself, by simply setting the FSB from 1333 to 1400 to go from 2.66Ghz to 2.8Ghz, and even that small increase wasn't stable during gaming.

I have tried for hours today, including by experimenting with upping the voltages, to try and get the system stable at even 2.8Ghz, but it's not having it. The RAM is unlinked and running at its stock 800Mhz although I did try underclocking the RAM to run 1:1 with the FSB, e.g. if FSB was 1400 then I set the RAM to 700Mhz. It had no effect.

Can anyone see any reason why this system won't accept a stable overclock, not even a little? The temps are all fine.

Ps) I get the feeling this seller had the same problem. I believe he built this machine as a gaming rig for overclocking hence the massive heatsink etc, realised it won't overclock so flogged it. It can't have been stable for 3 months as the receipts that came with it show he bought most of the components only 2 weeks ago.

 

[jedimasterben]

just remember the I7 alone @ stock speeds or down clocked uses an average of 45w idle and once over clocked its using 150+watts and thats why it gets so hot and requires alot more PS if you are going to overclock same goes for your GPU's overclock=power usage! so start with more PS then you need if you are gonna overclock later.

What does th i7 have to do with anything?

 

[Twoboxer]

Here's an example review citing a C2D X6800 using 302W at 100% CPU with a single WD raptor. Adding 2x260 at nVidia max spec adds 2x182 = 364W for a total of 666W.

http://www.guru3d.com/article/geforce-gtx-260-review/4

While there's usually headroom in a vid card manufacturer's spec, that total gets a little too close to 700W to say any 700W psu will easily handle it. Most probably will, most of the time. Maybe every time.

If this were a new system build I wouldn't go with a 700W psu. But in an existing build I wouldn't replace a 700W psu immediately either.

 

[lucuis]

Don't forget all those Power Consumptions are tested at the outlet. You then have to factor in PSU efficiency.

For Example: You take Twoboxers estimate on 666watts pulled for gtx260sli. Let's assume the machine is running an a decent PSU with 80% efficiency across the board and is capable of producing 700watts rms. If it's pulling ~666w it's then producing ~532.8w, the computers actual power consumption. That leaves the PSU with a theoretical headroom of ~167.2w

Keep in mind the way quality PSUs are rated. They're rated at how much they can produce, not how much they pull.

In other words the current 700w PSU will do just fine with the OPs system.

 

[Twoboxer]

Good point, Lucuis. And I may have fallen into that trap. That review did not describe how it measured power consumption, other than this enigmatic statement:

"We have a device constantly monitoring the power draw from the PC."

In any case, if power draw is measured at the wall we can safely reduce the 302W to 270W. Then add back the 364W manufacturer's spec for the 2x260 because I *hope* that isn't "measured from the wall".

Anyhow, 634W does mean a 700W psu with the right 12V capacity should work OK.

 

[ewood]

so the system is stable at 3.12v now? do soem torture tests and get back to us! im glad your didnt get totally screwed