In the race to 1GHz it seems that the 900MHz Athlon has been all
but forgotten. In the course of 3 months AMD has released the Athlon 800,
850, 900, 950, and 1000Mhz processors, so you can see how it could be easily
fall through the cracks. The 900MHz doesn't share the mystique of the
1GHz, but of course it doesn't cost near as much either. In this review
I'll take a look at the 900MHz Athlon and compare it to the 750 and 600MHz
versions. First let's take a look at the Athlon specs.
7th Generation design
9 Operations per clock cycle
3 Integer pipelines
3 Floating point pipelines
3 Full x86 decoders
128KB L1 cache
512KB L2 cache (off die)
200MHz System bus speed
1.6GB/s peak bus bandwidth
45 3DNow! instructions
~22 million transistors per die
Impressive specs when they were unveiled back in June, and they
still are today. Here's a diagram of the architecture of the Athlon.
I won't make an attempt to even explain how everything works. For more
info I suggest visiting the Athlon
technical documents page at AMD.
I first came across the 900MHz Athlon at Comdex
back in November. AMD was showing a 900MHz system that was air cooled at
the time. I didn't expect to see it released until the 2nd or 3rd
quarter, but now a mere 4 months later I am reviewing it. Now the design
of the Athlon has allowed for a quick ramp up in MHz, but there are a few
changes that may not be apparent on the outside. Let's take a look at a
few key specs of the Athlon 900 and compare them to the 600 and 750 MHz models.
||L2 Cache divisor/speed
||Model 2 .18 Micron
||Model 2 .18 Micron
||Model 1 .25 Micron
A quick look at the above chart will tell you several things. The
900MHz is of course a model 2, or K75 core. This means that it was made
with the .18 micron process. Next take a look at the L2 cache speed.
As speeds of the Athlon has gone up, speeds of L2 cache sadly, have not.
There is just not enough high speed SRAM available to keep the L2 cache divisor
at 2/5 or 360MHz, much less the 450MHz that would be required for a 1/2
divisor. This has forced AMD change the cache divisor to keep speeds at
300MHz. This will have a negative effect on performance and will cause
diminishing returns as speeds rise. Now take a look at the core
voltage. AMD has used a little trick long used by the overclocker.
They have raised the core voltage .2V to 1.8V. Raising it helps stabilize
the CPU at higher speeds, but also raises the heat put off by the
processor. Lastly, take a look at the watts of the Athlon 900. The
maximum watts has increased a full 33% over the 750MHz model. This is
merely a by-product of the MHz race with *ntel.