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Installing RAM

Memory Problems

May 29, 1999
By David Risley

There are a lot of problems out there to be had with memory. That's why it isn't too fun. Most of the time, these errors can be traced simply to faulty SIMMs. Nevertheless, let's look at some common memory errors, just so you know and you can impress your friends.

Two very common memory errors are

NMI error at [address] or Memory parity interrupt at [address]

If you have Phoenix BIOS, it goes on:

Type (S)hut off NMI, (R)Reboot, (I)gnore

An NMI is a nonmaskable interrupt. This means that your computer isn't allowed to mask this one while finishing another task. When an NMI occurs, you'll know. The whole computer will lock up and will stay dead until you fix the problem.

Most PCs reserve a chunk of memory so that it can test the rest of the memory. Almost all modern computers use non-parity memory. These computers will not generate an NMI if it finds only one bit or so bad during the test. With these non-parity computers, then, you may get a few random errors in your work due to these bad bits that the memory test hides.

So, what causes this parity error? Most likely you have a bad RAM chip. Either that or the voltage to the memory dropped and your computer forgot everything.

To find error sources, though, usually requires a software memory test; there are several out there. Hopefully these programs can point out the bad chip so you can replace it. If you're lucky, the SIMM just slipped out of the socket somehow. All you have to do is snap the case off and reseat the chip.

If a testing program doesn't find anything, you'll need to have your memory tested at a repair shop.

If you suspect a voltage drop to the memory, as stated above, check to make sure you have sufficient power from the outlet on your wall. Most computers expect around 110 volts from the wall. You can test the outlet with a voltometer and see if you are indeed getting that much. Another possibility is a temporary brown out. This is when the power in your entire house reduces temporarily. This could be because of overloads at the power company in your area, or possibly a major electrical appliance in your house, such as an A/C, powering up.

Besides these, there could be a myriad of problems. You may need to replace your power supply. The most drastic measure: replace the motherboard or all of the SIMMs.

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