The FSB is the bus on the motherboard with which the processor communictes with the RAM, chipset and L2 cache. Speeds are usually 66,100 and 133 MHz.
Well, the FSB is the bus that the CPU communicates with outside world, not necessarily with the cache, the chipset or memory alone.
Cache is very personal to the processor, independent of memory and could run at the full CPU speed (not the FSB but at full CPU speed that is FSB*multiplier) if its on-die , or at half or a third the speed if its off-die cache or at a certain asynchronous speed if its off-die, off-module third party chips integrated on the motherboard.
Chipset these days is the processors's Personal Assistant that manages <i>EVERYTHING</i> for the processor including memory accesses, I/O accesses to interrupts! I could well make a design <i>without</i> a chipset, but then I would need to connect different chips that will work different things for the processor. The chipset also serves as a interface for any kind of memory, a kind of translator for the processor. the memory controller in the chipset can work with any kind of memory, be it a SDRAM, a DDR-SDRAM, VCRAM or RDRAM, but it will talk to the CPU in its own native bus. 64 bit DDR link for the AMD processors and 64 bit SDR for Intel P3 family processor, or 64 bit Dual channel Dual pumped bus for Intel P4 family of processors.
Memory, as I said, does not directly communicate with the processor, but the memory controller in the chipset. that is why it could run independent of the processor FSB. many controllers decouple the CPU/memory bus so that you could use a faster processor with slower memory.
The speeds are usually 66, 100 or 133 MHz, but earlier Intel Pentium processor some Cyrix processor do work with 60, 75 or 83 MHz FSB! before that, there was no FSB concept and the processor worked at the same speed as that of the bus. the first processor to use a multiplier was the 486DX2/66 that ran at a FSB of 33 MHz and clock multiplied by 2 to run at 66 MHz internally. it was followed by DX4/100 with 33 * 3, DX2/50 and DX4/75 that had 25 MHz FSB!
the DDR FSB of AMD processors is a ingeneous trick that effectively doubles the memory access speed by transferring data twice at each cycle, while traditional processors did it only once.
Memory PC66, PC100 & PC133 should be self explainitory. PC1600 & PC2100 are for the 200 & 266 DDR systems respectively
all SDRAMs are named by their operating speed while DDR and RDRAMs are designated by their transfer rates. those are different!
PC66, PC100, PC133, PC150 are obvious that run at 66, 100, 133 or 150 MHz speeds, this speed is the maximum the module can run at reliably, you might use it at lower speed and might overclock a bit as well!
with PC800, PC1600, PC2100, 800, 1600, 2100 etc are respective transfer rates in MB/sec of the memory modules.
girish
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