only 3 cores appear as working from quad-core

[demonikal]

One day I booted up my computer - no changes had been made to it, and it said something like "Cores 0, 1, 3" activated"" or "Cores 0, 1, 2" activated"". Yet, I have a quad-core CPU, an AMD Phenom II X4 955 (3.20GHz).

What could have happened? Did one of the cores overheat perhaps and just stop functioning? I went into Device Manager and again, only 3 of my 4 cores are listed.

Is there anything I can do without having to pull it out by hand - I mean, in terms of troubleshooting. I bought it in 2011.

 

[Geoff]

What shows up in the BIOS? I believe there is a BIOS setting that could have caused this.

 

[demonikal]

What shows up in the BIOS? I believe there is a BIOS setting that could have caused this.

It was set on Cores 0, 1, and 3. I had the choice of choosing Cores 0, 1, and 2 and then also all 4 Cores. I chose 4 Cores. I wish I knew how I could really test the computer to see if it will stay this way, but I guess the only way to know is to leave it running with 4 Cores for 24 hours or so. I'll follow-up with all the settings in my next post. Most of my settings though are set to Auto. I've never tried overclocking anything. Really no need to, since I'm not running high-end anything on this thing (was really no point in ever getting 16GB of DDR3 RAM for instance ).

I forgot I could make that change in BIOS though. Thanks! Like I said, I'll follow-up with settings in next post.

 

[demonikal]

Everything I think that someone would need to know:

Motherboard: ASUS M4A78T-E

Main/System Information-

Bios Information
Version: 2208
Build Date: 10/28/09

Ai Tweaker-

Ai Overclock Tuner - Auto
CPU Ratio - Auto
DRAM Frequency - Auto
CPU/NB Frequency - Auto
HT Link Speed - Auto
-------------
CPU Voltage - Auto
CPU/NB Voltage - Auto
CPU VDDA Voltage - Auto
DRAM Voltage - Auto
HT Voltage - Auto
NB Voltage - Auto
NB 1.8V Voltage - Auto
SB Voltage - Auto
-------------
CPU Spread Spectrum - Auto
PCIE Spread Spectrum - Auto

Advanced/CPU Configuration-

AMD Phenom II X4 955 Processor
Revision: C3
Cache L1: 512KB
Cache L2: 2048KB
Cache L3: 6MB
Speed: 3200MHz, NB Clk: 2000MHz
uCode Patch Level: 0x10000AF
-------------
GART Error Reporting - Disabled
Microcode Updation - Enabled
Secure Virtual Machine Mode - Enabled
Cool 'n' Quiet - Enabled
ACPI SRAT Table - Enabled
C1E Support - Disabled
Advanced Clock Calibration - Auto
Unleashing Mode - Enabled
Active CPU Cores - 4 Core Operation

*Too bad you can't use Alt + PrintScreen in BIOS

So far so good. My computer is sticking with the 4 core change. The computer wanting to go back to 3 cores happened a couple months ago. I'm pretty sure I tried changing it (and then forgot how I did it), but it refused to stay with the change (the default since this is a 4-core CPU).

Thanks for any help.