I’m having a problem with my computer booting up with GPU1 in it and monitor going black (turning off) with GPU2 in it. I’m not running them in quad SLI, just switching GPU1 and GPU2 and getting different errors.
 
When error occurs, I get Mobo Award Post Code “26”. My user’s manual defines code 26 as follows: Name - Clock Gen
Description – Init onboard clock generator and sensor
 
 
Ok, here’s the description of what’s been going on:
I get up in the morning and computer boots just fine with GPU1 in it and I have no problems running it for hours or all day but when I turn it off or try to restart, it usually won’t boot into bios but fans and other peripherals get power. Mobo digital post always says “26”. If I give it several hours (cooling off?) it will usually boot up again but bios tells me the mobo is in safe mode (due to failed attempts to start) and says I may need to adjust clock settings, press delete to enter setup or F1 to continue.
 
When I install GPU2 it will boot but screen will go black at varying lengths of time. Sometimes it will go for up to an hour and other times it won’t make it through windows startup. If I turn it off with GPU2 still in it, it will do the same thing, start and eventually go black.
 
I checked my ram by rotating single sticks in different slots etc. but that had no effect. EVGA eventually did an RMA on the Mobo but I’m having the exact same problem with the replacement Mobo so I called tech support again.
 
This time the tech told me it had to be my power supply and there was nothing else they could do for me. He said the power supply was the only link in the equation that was left so that’s what had to be wrong with it.
 
I don’t doubt that it is possible my PSU is the cause but I question the validity of such a diagnosis due to the fact that none of the techs I spoke with considered clock settings other than one tech who asked me to verify that my ram timings and voltages were set to Corsair suggested settings, which they always have been. I don't over-clock anything or mess with any of the default settings other than enable/assign raid-0 etc.
 
Any ideas?
 
My system specs are listed below:
 
CPU: Intel Core 2 Extreme QX9650
MB: NVIDIA nForce 790i Ultra SLI
GPU 1: EVGA GeForce 9800 GX2
 GPU 2: EVGA GeForce 9800 GX2
Memory: 4 x 1GB DDR3 Corsair 1333mhz (CM3x1024-1333C9DHX)
PSU: Enermax Galaxy 1000 watt nVidia SLI certified 24 pin ATX five rail modular psu
 

If I had another PSU that could run my system, I’d swap it out in a hot second but I’ll have to throw down a good chunk of change to buy a new one so I would like to be sure it really is the PSU before buying a new one.
 
Maybe someone can explain how the PSU will boot up and run fine indefinitely with GPU1 until shutdown but then wont reboot until system apparently cools down for an hour or two? The GPU1 cores run at about 79°C & 68°C with fan speed at 100%. Is that normal?
 
Processor cores run at 105°F, 110°F, 120°F & 125°F (liquid cooled). Is that normal?

I think it is one of three things that is probably the problem

1) Bad PSU     or

2) Bad Video Card     or

3) Video Card slot on Motherboard is faulty.

*You could always get a PSU to test, then return it within the time of that stores returns policy.

Here ya go.....save a copy of it in case you need it in the future. I also print it so, when I am adjusting BIOS settings I can document them and not have to try and remember what I did.

Please completely fill it out and make sure add the values showing next to any settings that are on AUTO. Thankx.
BIOS Version: P0[]
**System **
CPU Freq, MHz:[] GHZ []
FSB Reference Clock, MHz:[]
CPU Multiplier: [X]Bus Speed MHz []
PCle x16-1 & 16-2, MHz:  [100]
PCle x16-3, MHz:  [100]
SPPc->MCP Ref Clock, MHz:  [200]
nForce SPP --> nForce MCP:   [5X]
nForce SPP c-- nForce MCP:   [5X]
 
**Spread Spectrum**
CPU Spread Spectrum: [Disabled]
HT Spread Spectrum: [Disabled]
PCle Spread Spectrurn(SPP): [Disabled]
PCle Spread Spectrurn(MCP): [Disabled]
SATA Spread Spectrum: [Disabled]
 
**FSB & Memorv Config**
FSB - Memory Clock Mode:[]
FSB - Memory Ratio: []
FSB (QDR), MHz: []
Actual FSB (QDR), MHz:[]
x MEM (DDR),  MHz:[]
Actual MEM (DDR), MHz:[]
P1: [AUTO]
P2: [AUTO]
 
**Memory Timing Setting**
Memory Timing Setting: []
tCL (CAS Latency):[]
tRCD:[]
tRP:[]
tRAS:[]
Command Per Clock: [T]
 
** Advanced Memory Settings **
tRRD: [Auto] []
tRC: [Auto] []
tWR: [Auto] []
tWTR: [Auto] []
tFAW: [Auto] []
tREF: [Auto] []
tRFC: [Auto] []
**System Voltages**
CPU Core: [Auto] []
CPU FSB: [Auto] []
Memory: [Auto] []
nForce SPP:[Auto] []
nForce MCP:[Auto] []
GTLVREF Lane 0: [Auto] [] 
GTLVREF Lane 1: [Auto] []
GTLVREF Lane 2: [Auto] []
GTLVREF Lane 3: [Auto] []
 
**CPU Configuration**
Limit CPUlD Maxval:[Disabled]
Intel Speedstep:[Disabled]
xPPM Mode: [Native]
CPU Thermal Control: [Enabled at least-TM2]
C1E Enhanced Halt State:[Disabled]
Execute Disable Bit: [Enabled]
Virtualization Technology:[Disabled,if you do not use VT]
CPU Core 0: [Enabled]
CPU Core 1: [Enabled]
CPU Core 2: [Enabled]
CPU Core 3: [Enabled]

OK...please make these initial adjustments (in red) and see how well they help.

BIOS Version: [ P10 (12/30/2009) ]
**System **
CPU Freq, MHz: [3000.0 ]
FSB Reference Clock, MHz: [1333.3]
CPU Multiplier: [9]
Bus Speed MHz []
CPU N/2 Ratio: [Disabled]
PCle x16-1 & 16-2, MHz:  [Auto-100 ]
PCle x16-3, MHz:  [Auto-100]
SPPc->MCP Ref Clock, MHz:  [Auto-200]
nForce SPP --> nForce MCP:   [5X]
nForce SPP c-- nForce MCP:   [5X]
 
**Spread Spectrum**
CPU Spread Spectrum: [Center Spread]Disabled
HT Spread Spectrum: [Auto]Disabled 
PCle Spread Spectrurn(SPP): [Disabled]
PCle Spread Spectrurn(MCP): [Auto]Disabled 
SATA Spread Spectrum: [Disabled]
 
**FSB & Memorv Config**
FSB - Memory Clock Mode:[linked]
FSB - Memory Ratio: [Synced]
FSB (QDR), MHz: [1333]
Actual FSB (QDR), MHz:[1333.3]
x MEM (DDR),  MHz:[1333]
Actual MEM (DDR), MHz:[1333.3]
P1: [AUTO]
P2: [AUTO]
 
**Memory Timing Setting**
Memory Timing Setting: [Expert]
tCL (CAS Latency):[9]
tRCD:[9] Verify these are manually set to 9-9-9-24
tRP:[9]
tRAS:[24]
Command Per Clock: [1T] Manually set to 2T
 
** Advanced Memory Settings **
tRRD: [Auto] [4]
tRC: [Auto] [33]
tWR: [Auto] [12]
tWTR: [Auto] [16]
tFAW: [Auto] [21]
tREF: [Auto] [7.7uS] Manually set to 7.8uS
tRFC: [Auto] [60]
**System Voltages**
CPU Core: [Auto] [1.19]Manually set to 1.3v 
CPU FSB: [Auto] [1.1] Manually set to 1.1v
Memory: [Auto] [1.5] Manually set to 1.6v
nForce SPP:[Auto] [1.30] Manually set to 1.45v
nForce MCP:[Auto] [1.500] Manually set to 1.55v
GTLVREF Lane 0: [Auto] [-30mv] 
GTLVREF Lane 1: [Auto] [-30mv]
GTLVREF Lane 2: [Auto] [+00mv]
GTLVREF Lane 3: [Auto] [+00mv]
 
**CPU Configuration**
Limit CPUlD Maxval:[Disabled]
Intel Speedstep:[Auto] Disabled
xPPM Mode: [Native Mode]
CPU Thermal Control: [Disabled]
C1E Enhanced Halt State:[Enabled]Disabled
Execute Disable Bit: [Enabled]
Virtualization Technology:[Enabled] Disabled if not using VT
CPU Core 0: [Enabled]
CPU Core 1: [Enabled]
CPU Core 2: [Enabled]
CPU Core 3: [Enabled]

Sorry for taking so long to report back.
 
I made the bios revisions and it seemed to help at first but, typical for this problem, issues came back but with different symptoms.
 
I bought a 775W Thermaltake Toughpower XT and installed it today. Booted right up with no problems no matter which GPU I had in it and it’s even running in quad SLI right now.
 
I’m pretty sure the PSU was indeed the problem but I’m going to play some Starcraft II (have some catching up to do) on highest settings possible and maybe even throw some Crysis at it before I consider it fixed due to the intermittent nature of the problem.
 
I’ll let you know if it stays fixed or has problems again. Thanks to everyone who helped out.
 
Andrew

Status report:
 
Computer failed to boot twice while in quad SLI mode the last two mornings; each time after playing Starcaft II for a few hours the night before.
 
I had to power on and off several times but it eventually started the first morning after I had replaced the PSU. This morning however, I had to remove the SLI bridge to get it to boot. I was able to get it running in quad SLI again and have been able to shut down and power up all day without any problems other than the initial startup.
 
I’ll give it 2 or 3 more mornings of evaluation before I proclaim the problem solved.
 
As for the BIOS adjustments, I haven’t changed them.

I made the changes you suggested when you posted them. I haven't messed with them since then and don't see any reason to in the future.
 
 

Other than the first two mornings I described earlier, I haven’t had any problems….until this morning.
 
Booted up and started using computer about 6am this morning then took a shower around 9:30 and tried to boot up again at 10:00am. It wouldn’t boot into Windows no matter what I did.
 
I removed SLI bridge, then removed the extra GPU, then switched the GPUs and nothing. It just wouldn’t boot.
 
I ran over to Fry’s and grabbed an EVGA GeForce GTS 250 and plugged it in and it booted right up.
 
After a little time, I plugged the 9800s back in (quad SLI), single GPU1 only, single GPU2 only and same thing (error 26) every time. I plugged the GTS 250 in and it booted right up.