CPU Rubber Gasket: The CarrierZIF (and Apple) ZIFs both use a gasket around the CPU chip that serves to help take stress from the heatsink off the CPU contact area of the chip (the center raised area of the CPU). The CarrierZIF comes with an adhesive backed rubber gasket for this purpose. Before applying it, first check to see if your CPU already has this gasket. All Apple Beige/B&W G3 ZIFs ship wiht a gasket already applied, as do some OEM ZIFs sold by other companies. I've heard some owners have applied a 2nd gasket on top an existing one - double gaskets will prevent the heatsink from contacting the CPU and result in overheating and failures.

Checking for Existing CPU Gasket: The photo below shows two Other World Computing ZIF CPU modules - one 350MHz (left) and a 400MHz (right). You can read the Motorola text on the edges of the left CPU, which shows it has no gasket. Look at the CPU on the right - notice it already has a gasket around the edge of the CPU chip. Don't apply the CarrierZIF gasket to any CPU that already has one.

CPUs with and w/o Gaskets

The 400MHz model already has a gasket but CPUs like the one on the left will need to have the XLR8 gasket applied.

Note: Be careful when peeling off the adhesive backing on the gasket to make sure you are removing only the paper, not the adhesive film. In my first try the adhesive layer stayed on the paper not the rubber gasket. With care (and fingernails), you can peel off only the paper and leave the shiny adhesive film layer on the rubber gasket.

Glossy Layer is Adhesive Film

Position the gasket over the CPU making sure it clears the surface mount chip capacitors on the CPU (it should lay flat - not bunched up).

Gasket Applied to 350MHz ZIF

Installing a ZIF Module: Installing the ZIF CPU module in the CarrierZIF requires lifting the locking lever of the ZIF to a fully vertical position. The lever is retained in the locked (down) position by a small tab on the ZIF socket side. Some lateral pressure is required when lifting the lever up to release it.

Before installing the ZIF module carefully examine the pins on the bottom of the module. They should all be vertically straight (not bent). Locate the missing corner pin on the ZIF module and match it to the ZIF socket corner that has no pin socket (see the photos above). Do not force the module in the socket - if it doesn't drop in easily with very little pressure double check the pin orientation. If you accidently bend a pin you can a) try to straighten it (if you're experienced and its not bent very much) or b) talk to the ZIF vendor for repair/replacement.

Once the ZIF CPU module is fully inserted in the ZIF socket (there should be no gap between the ZIF module and the socket), lower the locking lever down and press firmly so make sure if snaps in place (the previously mentioned tab on the socket helps retain it in the down position).

Applying Thermal Compound: The CarrierZIF comes with a small container of thermal compound (paste) that you apply to the area of the CPU that contacts the heatsink. This improves the transfer of heat from the CPU to the heatsink and 'fills in' any imperfections (lack of flatness) in the CPU or heatsink contact area. The photo below shows me applying the paste to the CPU contact area with the XLR8 supplied wood applicator.

Applying Thermal Paste to CPU

Apply an even layer of compound. XLR8 recommends applying about the same amount as the thickness of the rubber CPU gasket.

Mounting the Heatsink: The final assembly step is to mount the heatsink. Position the heatsink so the notches are toward the CPU card connector and the right edge of the card when viewing it from the red speed switch side (see photo below).

Latching the Heatsink Clip

Making sure the heatsink clip end with two holes is facing the speed switch side of the card, place the clip over the ZIF socket tab on the other side and then press it down to lock on the nearside ZIF socket tab.

[Heatsink Retainer Removal Note: A reader said he snapped off the ZIF socket tab that retains the heatsink retainer when trying to remove the clip. The proper way to release the heatsink retaining strap is to use the supplied small screwdriver tip in the 2nd hole in the end of clip while pressing down and out to clear the plastic ZIF socket tab - see this photo for an example.]

Now that the card is fully assembled, you're ready to set the operating speed (bus speed and Bus/CPU ratio). The next page of this guide covers details on speed settings for the system bus, CPU and Backside Cache. Or you can use the links below to jump to another part of this guide or other related links.