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| Basic Troubleshooting |
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Computer Article Last Reviewed July 2009 |
 RAM | ||
 When you boot your OS (operating system) or launch an application, your computer grabs data off the hard drive and stores most of it in solid state RAM, or random-access memory. RAM is much faster than a hard drive or other storage medium, so it makes a computing session more responsive and the user more productive. However, if there’s a minuscule defect anywhere in a RAM module’s silicon chips, and it drops a 0 or a 1, the file stored in that location becomes corrupted. The result is that your OS or application will crash, freeze, or report errors. This article tells you how to troubleshoot RAM with universal testing tips as well as solutions for common problems. For stability reasons, we’ll assume you’re running your RAM at its rated speed, voltage, and timing specifications. You can find these by searching for the RAM’s model number on the manufacturer’s site, and you can verify and/or adjust them in many motherboard’s BIOS (Basic Input/Output System) Setup (during bootup, press DELETE, ESC, or the indicated key).  The Very Model Windows won’t tell you a DIMM’s (dual inline memory module) brand and model number, so shut off your PC and pop open your computer case. Remove one of your RAM modules by pressing the retention clips on either end of the module downward (toward the motherboard). As the clips pivot away from the DIMM, they’ll simultaneously lift it out of the slot.
Hopefully a label on the module's chips or metal heat spreader will tell you the module's brand and model number, such as Corsair CMX256A-3200C2. There may be several similar alphanumerical markings, so be prepared to search for each marking on the manufacturer’s site until you can confirm which one is the model number. Don’t look up the numbers printed on individual memory chips, however, as most DIMM manufacturers build their modules using RAM chips from semiconductor foundries such as Samsung. Universal Troubleshooting Steps Bad RAM can manifest itself in various error messages, application hangs, and OS crashes. If malware scans come up clean, System Restore doesn’t help, and your computer’s power supply is known to be good, RAM should be your prime suspect in this case. Memtest86 (www.memtest86.com) is free RAM testing software that's extremely easy to use. After you download it, you can create a bootable CD or floppy diskette with it, depending on the version you choose. Restart your system with the bootable medium in its drive, and Memtest86 will automatically test your memory until you press ESC to stop it. (Make sure your floppy or CD/DVD drive comes before the hard drive in your PC’s boot device order in the BIOS.) You should allow the utility to run at least one complete pass, which may take most of an hour. We downloaded Memtest86 3.2 as an ISO (International Organization for Standardization) file by clicking the self-explanatory link. We then used the free IMGBurn utility (www.imgburn.com) to create a bootable CD. At this writing, the link to the floppy version’s handful of files was called Download – Pre-Compiled Memtest86 v3.2 Installable From Windows And DOS. To make a bootable diskette with it, run the file called Install.BAT. Both Memtest86 downloads are compressed in the ZIP format, so if your OS can’t open ZIPs as WinXP and Vista can, use a compression utility such as WinZip (www.winzip.com) to extract Memtest86’s ISO or files.
Troubleshooting errors. If your diagnostic utility reports any errors, turn off your PC and remove all but one stick of RAM. Rerun the memory diagnostic for a while with each DIMM by itself until you’ve isolated the module with a problem. Try the troubleshooting solutions in the section below, as applicable. If you have access to another PC that uses the same type of RAM, put your suspect memory in it and run Memtest86 on that computer. If no errors surface, the RAM might be incompatible with the memory controller in the original motherboard’s chipset (for Intel-based PCs) or in the processor (for AMD Athlon 64, X2, Sempron, and FX-based computers). If a DIMM causes errors consistently or intermittently on both PCs, you can bet it’s defective in some way. Contact the reseller or manufacturer about replacing it or getting a refund. Lapses Of Memory Sometimes bad things happen with good RAM. Here’s a list of common problems and possible fixes. Problem: Errors start only after the PC has been running for a few minutes or during heavy workloads. Solution: Check that the PC’s fans are all running and that there is decent airflow over the RAM and other devices. Carefully blow out any dust. Also, verify in the BIOS that the RAM is running at its specified voltage, such as 2.2v. Problem: Your RAM works with one motherboard, but not another. Solution: Check the motherboard manufacturer’s site for compatibility with specific brands and model numbers of RAM modules. Note that some motherboards may be compatible with particular sticks of memory only at slower timings (such as a CAS [column address strobe] setting of 4 or 5) or FSB (front side bus)/system bus/HyperTransport speeds, such as 667MHz. Timings refer to how often (usually in CPU clock cycles) different operations happen in the RAM, whereas the FSB/system bus/HT speed describes the rate of data transfer between the RAM and the CPU. You may be able to change some or all of these settings in the BIOS. Other boards may require you to slightly increase the voltage to the DIMM slots in order to get the RAM to run stably. Problem: The RAM is approved for your motherboard, but it’s still causing problems. Solution: Try different DIMM slot(s). Consult the motherboard’s documentation to determine which slots should work best with the number and size of your RAM module(s). Problem: You can’t run your RAM in dual channel mode, which allows the CPU to access both sticks simultaneously for a slight performance gain. Solution: Both the motherboard and processor must support dual channel memory access. For example, a 939-pin Athlon 64 CPU supports dual channel, but a 754-pin Athlon 64 CPU can’t. Also, you must place the pair(s) of DIMMs in particular slots, which are color-coded on some motherboards. Dual channel mode may not work well unless you use identical RAM modules. Problem: The metal heat spreader covering the module doesn’t touch all the chips. Solution: Your best option is to send the RAM module back for replacement, if it’s still under warranty. If your warranty coverage has run out, you can try removing and reseating the heat spreader. Buy some double-sided thermal tape from an enthusiast site such as FrozenCPU.com. Next, carefully work off the heat spreader’s clips with a small screwdriver. Remove the metal heat spreader halves, then clean the old tape residue from it and the DIMM’s chips with isopropyl alcohol. If either heat spreader piece is bent, straighten it so that it will make better contact with the chips. Apply new thermal tape to the heat spreader halves, then attach them to the RAM module in the correct positions. Squeeze the spreader halves firmly over each pair of chips to help the thermal tape adhere, then reattach the spreader’s clips.  by Marty Sems |
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