Bad Ram Slot Symptoms

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Bad Ram Slot Symptoms

So far, in terms of failure modes with bad RAM slots, either any RAM in that slot is not recognized and ignored, or else the system won't boot with any RAM in that slot, either locking up during POST or black screen before POST, sometimes with beeps. You can always get unlucky and just have some crappy ram sticks, and just not notice it until they finally decide to go south. Corsair just recalled a bunch of memory that went bad after a short time - high end ram tends to be unreliable like that.
Hello, I'm having issues with my iMac (27', late 2009), and after some troubleshooting still can't figure it out so I thought I'd ask here.

The first time I noticed a problem was when I booted up a couple of days ago. The screen had random pixels transplanted all over the place, and if I attempt to perform simple tasks such as moving windows or simply clicking on icons, the system freezes up -- when that happens I can still move the mouse pointer around but that's all I can really do, and have to hard shut down.

I then tried using the CD with the Apple Hardware Test (i.e. together with holding 'D' key down while starting up), and it revealed the following error code --

4MEM/9/40000000: 0xb78df418
Bad Ram Slot Symptoms List
Upon researching this error code, it appeared that it was pointing to my RAM as a potential issue. I thus proceeded with the following steps --

1) removed and re-inserted the 4 RAM cards (no difference in symptoms)
Bad Ram Slot Symptoms Checker2) removed 1 RAM card one-by-one and tried starting up (to see if any 1 of the RAM cards was faulty, but no difference in symptoms)
3) tried starting p with just 1 or 2 RAM cards in certain RAM slot configurations

1) removed and re-inserted the 4 RAM cards (no difference in symptoms)
Bad Ram Slot Symptoms Checker2) removed 1 RAM card one-by-one and tried starting up (to see if any 1 of the RAM cards was faulty, but no difference in symptoms)
3) tried starting p with just 1 or 2 RAM cards in certain RAM slot configurations

#3 above is where it got interesting. I found that if either 1 or both of the back pair of RAM slots were used, and the front pair left empty, I would get 1 beep every 5 seconds upon starting up. If I just use 1 back and 1 front slot, the rig starts up fine, but still with the pixels. According to this, that's telling me the back pair of RAM slots is bad? The thing that confuses me is that when I only use the front pair of slots, I still get the pixels. So do I have a pair of bad RAM slots, and 4 bad RAM cards too? Is it possible for bad RAM slots to cause all RAM cards (even those in good RAM slots) to fail?
 iMac, OS X Mavericks (10.9.3) 
 Posted on Jun 4, 2014 12:56 PM 
Bad Ram Slot Symptoms TreatmentComputer Hardware‎ > ‎Internal Devices‎ > ‎ 
Common Symptoms and Diagnosing Bad Computer Memory (RAM)Common warning signs to pay attention to:
Bluescreens (bluescreen of death)
Random crashes or reboots
Crashing during heavy memory use tasks, such as gaming, Photoshop etc.
Distorted graphics on your computer screen
Failure to boot (or turn on), and/or repeated long beeps
Memory errors appear on screen
Computer appears to boot, but screen remains blank

Windows Vista, Windows 7 and later have a Windows Memory Diagnostics tool that can be easily accessed by clicking on Start, Control Panel, Administrative Tools, then MemoryDiagnostic Tool. (Running this diagnostic tool will give you two options, either restart immediate - or to test memory the next time the computer restarts. Choosing either of these options will run the computer through a memory test the next time it starts up.)
Another way to test your memory is by replacement with a known-good memory stick. If you do not have known-good memory available to you to test with, contact your computer manufacturer (Dell, Toshiba, Sony etc.) for assistance.
Solutions:
Perform a virus scan. Viruses can cause symptoms that mimic those of faulty memory.
Verify that your memory modules are fully seated. Check your documentation for your computer system, or contact your computer manufacturer if you are unsure how to do this.
Try swapping memory module slots - or - try booting with only one memory module if you have two modules installed.
Check for BIOS Updates (usually applies to older computers).

Hardware Diagnostics
Most computer manufacturers include a pre-installed hardware diagnostic utility, or other hardware assessment tool, which you can use to diagnose hardware problems. 
All Dell computers, for example, ship with a utility partition on the hard drive - Dell 32-bit Diagnostics. To run the Dell diagnostics:
Restart the computer. As the computer boots, press F12 on the keyboard when the Dell logo screen appears.
When the Boot menu appears, highlight the Boot to Utility Partition option, or Diagnostics option, and press Enter.
Press the Tab key to highlight Test System, press Enter.
Express Test will run a quick test, which can take 10-20 minutes.
Extended Test will perform a thorough check of the system, and can take an hour or more to complete.
Custom Test can be used to test a specific device.
Symptom Tree lists most common symptoms and allows you to select tests based on those symptoms.

If the diagnostics produce an error, or errors, contact Dell: 1-877-293-1197. 