Hardware Reference
In-Depth Information
Figure 3.8. PGA on Pentium 66 (left) and dual-pattern SPGA on Pentium Pro (right).
Early PGA variations mounted the processor die in a cavity under the substrate, whereas so-called
“Flip Chip” versions mount the processor die upside down so that less expensive solder bonding
rather than expensive wire bonding can be used to connect the processor die to the chip package.
Unfortunately, there were some problems with attaching the heatsink to an FC-PGA chip. The heatsink
sat on the top of the die, which acted as a pedestal. If you pressed down on one side of the heatsink
excessively during the installation process (such as when you were attaching the clip), you risked
cracking the silicon die and destroying the chip. This was especially a problem as heatsinks became
larger and heavier and the force applied by the clip became greater. Intel and AMD now use a metal
cap called a
heat spreader
over the top of the CPU to prevent damage when the heatsink is installed.
This type of packaging is known as FC-PGA2 and was used by Intel for all Pentium 4 and subsequent
chips. AMD began to use it with its Athlon 64 processors and subsequent chips.
Future packaging directions may include what is called
bumpless build-up layer
(BBUL) packaging.
This embeds the die completely in the package; in fact, the package layers are built up around and on
top of the die, fully encapsulating it within the package. This embeds the chip die and allows for a full
flat surface for attaching the heatsink, as well as shorter internal interconnections within the package.
BBUL is designed to handle extremely high clock speeds of 20GHz or faster but is not yet necessary.
Single Edge Contact and Single Edge Processor Packaging
Intel and AMD used cartridge- or board-based packaging for some of their processors from 1997
through 2000. This packaging was called
single edge contact cartridge
(SECC) or
single edge
processor package
(SEPP) and consisted of the CPU and optional separate L2 cache chips mounted
on a circuit board that looked similar to an oversized memory module and that plugged into a slot. In
some cases, the boards were covered with a plastic cartridge.
To learn more about SECC and SEPP packaging, see “Single Edge Contact and Single Edge
Processor Packaging” in Chapter 3 of
Upgrading and Repairing PCs,
19
th
Edition, included in its
entirety on the disc packaged with this topic.
Processor Socket and Slot Types
Intel and AMD have created a set of socket and slot designs for their processors. Each socket or slot
is designed to support a different range of original and upgrade processors.
Table 3.10
shows the
