I am doing some research to buy a computer. I don't know what the
difference is between:
CPUs:
AMD K8 Sempron64 754P 2600+
AMD K8 Sempron64 754P 2800+
AMD K8 Sempron64 754P 3000+
What are these numbers: 2600+, 2800+, 3000+ ? Is this related to the L2
cache memory?
RAM Memory:
DDR 512MB 266MHz PC2100 Corsair
DDR 512MB 333MHz PC2700 Corsair
What do PC2100 and PC2700 mean?
Thank you,
Go here and click "View all products". The Sempron
stats are near the bottom of the page.
http://www.amdcompare.com/us-en/desktop/Default.aspx
Here is a mini-primer on DDR.
They put memory chips on the DIMM, and try to make a
64 bit wide memory array. When they do that, that is
a "bank" or "side" of memory. Double sided memory
means enough chips are used to make two 64 bit wide
banks of memory, and the memory chips sit in parallel
on the memory bus. (Memory chips come in widths of
x4, x8, and x16, so the chip count needed varies,
depending on the width used for each one.)
As for the math, if we start with a 133MHz memory clock
signal and connect it to the memory chip, the memory chip
is DDR (double data rate), meaning data is transferred
on both edges of the clock signal. Each memory transfer
is 64 bits of data (8 bytes), which will be going to a
bank of memory. Thus, the bandwidth is
Bandwidth_DDR = clock x 2 x (8 bytes per transfer)
= 133 x 2 x 8 = 2128
= rounding a bit gives PC2100
In other words, the PCxxxx part is a bandwidth specification
in MB/sec theoretical max rate. The DDRxxx part is the
number of megatransfers per second, each being 8 bytes of
data.
A faster memory can be run at slower speeds, so a PC3200
memory can be run with a memory clock of 100, 133, 166, or
200MHz, giving bandwidths of 1600, 2100, 2700, or 3200MB/sec.
If you buy a PC2100 memory, if can run with memory clock of
100 or 133, and cannot run 166 or 200 (it would be overclocked
if you tried it). So, a faster memory allows it to be used
in more different computers.
And yes, the P.R. rating does depend on the size of the
cache. It also depends on the core speed. Somewhere on the
AMD site, they'll tell you exactly which tests they use,
to develop the P.R. rating, but good luck getting anything
from the lousy AMD search engine.
The Sempron performance is compared to Celeron D, which is
why the numbers are so high. The other processors on the
AMD site, are compared to a P4, a tougher opponent.
http://www.amd.com/us-en/Processors/ProductInformation/0,,30_118_11599_11605~101503,00.html
Paul
