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Second, you can sometimes get away with putting one speed of DRAM in one bank and another speed in another bank, as long as all the speeds are as fast as or faster than the speed specified by the motherboard. Don’t bother trying to put different-speed DRAM sticks in the same bank with a motherboard that uses dual-channel DDR. Yes, it works once in a while, but it’s too chancy. I avoid it.

Installing DIMMs and RIMMs

Installing DRAM is so easy that it’s one of the very few jobs I recommend to non-techie folks. First, attach an anti-static wrist strap or touch some bare metal on the power supply to ground yourself and avoid ESD. Then swing the side tabs on the RAM slots down from the upright position. Pick up a stick of RAM—don’t touch those contacts—and line up the notch or notches with the raised portion(s) of the DIMM socket (Figure 6-27). A good hard push down is usually all you need to ensure a solid connection. Make sure that the DIMM snaps into position to show it is completely seated. Also, notice that the two side tabs move in to reflect a tight connection.

Figure 6-26 The motherboard book shows how much RAM the motherboard will handle.

Figure 6-27 Inserting a DIMM

Serial Presence Detect (SPD)

Your motherboard should detect and automatically set up any DIMM or RIMM you install, assuming you have the right RAM for the system, using a technology called serial presence detect (SPD). RAM makers add a handy chip to modern sticks called the SPD chip (Figure 6-28). The SPD chip stores all the information about your DRAM, including size, speed, ECC or non-ECC, registered or unregistered, and a number of other more technical bits of information.

Figure 6-28 SPD chip on a stick

When a PC boots, it queries the SPD chip so that the MCC knows how much RAM is on the stick, how fast it runs, and other information. Any program can query the SPD chip. Take a look at Figure 6-29 with the results of the popular CPU-Z program showing RAM information from the SPD chip.

Figure 6-29 CPU-Z showing RAM information

All new systems count on SPD to set the RAM timings properly for your system when it boots. If you add a RAM stick with a bad SPD chip, you’ll get a POST error message and the system will not boot. You can’t fix a broken SPD chip; you just buy a new stick of RAM.

The RAM Count

After installing the new RAM, turn on the PC and watch the boot process closely. If you installed the RAM correctly, the RAM count on the PC reflects the new value (compare Figures 6-30 and 6-31). If the RAM value stays the same, you probably have installed the RAM in a slot the motherboard doesn’t want you to use (for example, you may need to use a particular slot first) or have not installed the RAM properly. If the computer does not boot and you’ve got a blank screen, you probably have not installed all the RAM sticks correctly. Usually, a good second look is all you need to determine the problem. Reseat or reinstall the RAM stick and try again.

Figure 6-30 Hey, where’s the rest of my RAM?!

Figure 6-31 RAM count after proper insertion of DIMMs

RAM counts are confusing because RAM uses megabytes and gigabytes as opposed to millions and billions. Here are some examples of how different systems would show 256 MB of RAM:

268435456 (exactly 256 × 1 MB)

256M (some PCs try to make it easy for you)

262,144 (number of KB)

You should know how much RAM you’re trying to install and use some common sense. If you have 512 MB and you add another 512-MB stick, you need a number that looks like one gigabyte. After you add the second stick, if you see a RAM count of 524582912—that sure looks like 512 MB, not the one gigabyte!

Installing SO-DIMMs in Laptops

It wasn’t that long ago that adding RAM to a laptop was either impossible or required you to send the system back to the manufacturer. For years, every laptop maker had custom-made, proprietary RAM packages that were difficult to handle and staggeringly expensive. The wide acceptance of SO-DIMMs over the last few years