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PowerPC 602 Terminology Reference

This document makes an attempt to assist our readers in sorting out the terminology used in conjunction with the PowerPC 602. If you have any additional questions or comments, please feel free to contact us.

PowerPC 602 microprocessor
A leading new processor based around new RISC (Reduced Instruction Set) technology that is already used in many Power Macintosh computers. This new series of processors is very close to the same speed as the Intel Pentium based machines.
66 MHz (the PowerPC's operating speed)
This is the speed in which the Central Processing Unit (CPU) operates. This speed is similar to that of today's personal computers, which is much faster than the typical game console. The speed of the CPU is not the only factor in determining the overall speed of the machine, however. There are several components in a console including a graphics controller, sound controller, and more. The machine is only as fast as its slowest component.
32-bit data width
* Data width: width of the general purpose (integer/address) registers and integer ALU(s), in bits

This is how many bits of data can be processed in the ALU at one time. The ALU is the Arithemetic Logic Unit which does all of the key mathematical functions of the processor. The width of this is a major factor in determining the speed in which the processor can perform funtions like scaling and rotation.
64-bit bus width
* Bus width: external memory data bus width, in bits -- the memory bus can be, and often is, wider than the internal data path

This bus determines is a major factor in determing how fast the CPU can talk to all of the other chips in the Console. This includes the graphics processor, the sound processor and the memory. No console can run any faster than the bus allows. This is often reffered to as a major bottleneck in many machine designs.
Cache 4k/4k (the PowerPC's built in cache size)
* Cache: On-chip cache in kilobytes - two numbers means instruction/data

When a processor computes a mathematical problem it must have fast direct memory to read and write from. This is what the cache is for. The only memory the processor directly reads is the cache. Once the cache is full, the rest of the computer swaps the entire contents of the cache out to RAM, and brings in enough data to refill it again. This process is referreed to as paging.
Process 0.5u CMOS
This value is actually a measure of the size of the components used on the processor measured in mico-meters (or Microns). Usually the smaller the size, the more components, and thusly faster, the chip can be. Just becuase a chip has a smaller feature size does not mean that it is faster, only that it has the potential to be faster.
The importance of 64-bit architecture.
Imagine a giant lake trying to squeeze through a crazy straw... It wouldn't work. This is the same idea as trying to force tons of screen data through a small bus. Only with complete 64-bit design throughout the console can 64 bit speed be reached. If a processor can calculate at 64 bits, but the information can only reach it at 32 bits, that processor will be almost as slow as a 32 bit processor.
48 megabits of memory
The amount of memory that a system has determines how much calculated data can be stored to be later displayed on the screen, or used in later calculations. If the amount of memory is too low, high color full screen action won't work. The term megabit is actually 1/8 the common computer term megabyte. This means that 48 megabits is comparable to 6MB of RAM in your home PC.
memory subsystem capable of delivering 528 megabytes per second
This term shows the speed of the computers bus access to memory. Again, this is related to the computer bus width, as well as the bus speed.
MPEG-1 digital video decompression
This is the Moving Picture Expert Groups standard for compressed digital video. By having the compression chip needed to view this type of data the system promises crisp, fast, full motion video.
3-D perspective correction
A common problem with 3-D games is that they use simple trigometry to estimate rotations. In two dimesions this has little to no effect. However, in 3-D this often causes a skewed effect that makes the screen look as though you are looking thorugh a fish-eyed lens. Perspective correction does the extra trig. that keeps this effect from happening, and brings 3-D to higher levels of realism.

-The Ferrari Man

(for further detailed information, you may want to check out Motorola's PowerPC web pages on the subject)

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