Upgrading & Fixing Laptops DUMmIES

All you need to know is this: If your laptop requires ECC memory, you may not

be able to use non-ECC modules. And if your PC is not designed to work with

ECC, you can’t just plug in error-correcting memory and gain its advantages.

(In the best case, the memory works without ECC functions; in the worst case,

the system crashes or functions erratically with the wrong memory installed.)

And just for the record, ECC memory is more expensive and sometimes harder

to find than standard memory. Don’t buy it unless you need it.

Laptop memory module design .........................................................

Leaving aside the specifications for the memory itself, you also must match

the type of module to the available slot on the laptop. Among modern laptops

you find three forms of modules.

Proprietary cards

A proprietary card works only with a particular model or brand of laptop.

This may mean you have to buy replacement or upgrade modules from the

manufacturer at whatever price the company sets (that’s what I call a monop-

oly), or you may have to search for supplies from specialized suppliers.

You might want to shop for used proprietary memory modules from sources

on the Internet, including eBay auctions and from direct sellers. Be sure to

protect yourself against fraud by using a credit card or a guarantee offered by

an auction sight.

SODIMM

The most common current design is the Small Outline Dual In-line Memory

Module,better known to technodweebs (present company excepted) as

SODIMMS.A SODIMM is a SODIMM is a SODIMM, at least when it comes to

physical dimensions. The tiny cards are 5cm long by 2.5cm tall, or about

2 ×1 inch. Where SODIMMS can differ is in the number of pins that connect

to the computer’s bus; the more pins, the wider the pathway for data, and

higher the potential speed.

You find modern SODIMMS with 144 or 200 pins; an older class of SODIMM has

just 72 pins. This is a situation where you need to exactly match the needs

of the computer — if the socket has 144 connectors, the SODIMM must have

144 pins. Several modules are shown in Figure 6-2: An older-sized 72-pin

SODIMM is on the left; then there’s a higher bandwidth 144-pin SODIMM in

the middle. And finally, I’ve got a picture of a tiny, modern 144-pin MicroDIMM

on the right.

SODIMMs have identifying notches along the pin end of the module that pre-

vent installation of the wrong type of memory in a slot. Don’t ever try to force

a module into a slot that doesn’t readily accept the memory carrier; if it seems

92 Part II: Explaining What Could Possibly Go Wrong