Copper and CMOS Technology
The use of copper in chip design addresses several or the aspects that inhibit performance: power load, generated heat, clock signal distribution, and chip size.
The complexity of the chip design (roughly equated to the number of transistors) when combined with the lithography process determines the size of the die. The maze of interconnects between the circuitry over a large die, the voltage required to drive the circuits, and the clock speed of the chip (how often a circuit changes state) determines the power load and the heat generated. Heat affects the life of the chip. Specific areas of a chip, for example, an execution unit, can become hotter than other areas that operate less frequently and require extensive cooling. Also, the larger the chip, the more difficult it is to strobe a clock signal over the entire chip (electricity travels at the fixed speed of light). Because larger chips also require more area on a wafer, they are more expensive to produce.
Copper is a superior conductor of electricity, compared with the standard aluminum used previously. This equates to lower electrical resistance (40 percent less) and allows a smaller wire (interconnects) to handle the same electrical load. The smaller interconnects within the chip decrease the distance between components, reduce the heat generated, and decrease the clock skew over the chip making it possible to raise the clock speed without affecting reliability. This is particularly useful on the
However, copper does not work well with silicon, the base material of semiconductor chips. If copper is put directly on silicon, copper atoms migrate into the silicon, making it virtually useless. IBM researchers found a way to put a microscopic barrier between the copper and silicon in a way that keeps the copper from contaminating the silicon, while actually reduces the number of steps needed to complete a chip. With this development, IBM is able to reduce the widths of copper wires to about
This technology, called CMOS 7S, is the first to use copper instead of aluminum to create the circuitry on silicon wafers. This translates into an increased speed of up to 15 percent in processors that contain copper wires.
CPU Clock Rate
The different processor cards and the processor speeds can be identified by the SMS Display Configuration menu or by the following AIX command:
lscfg
Page down to the Processor Card entry and search for the Product Specification (ZC) entry. This gives detailed information about:
PS Processor Clock Speed in Hz, ASCII coded hexadecimal
LB L2 Bus Speed in Hz, ASCII coded hexadecimal
SB System Bus Speed in Hz, ASCII coded hexadecimal
NP Number of Processors on Card, ASCII coded hexadecimal
L2 L2 Size in number of Kilobytes, ASCII coded hexadecimal