| Intel's new "Coppermine"
CPU line is just coming out, so we thought it might be a good idea to go
over the differences between "Katmai" core and "Coppermine"
core CPUs. Intel is using an "E" to designate the new Pentium
IIIs. There are significant changes to this CPU, and in fact, this
is the first upgrade to the central "P6" core that was first
introduced with the Pentium Pro. In many ways, this new core deserves the
designation of "P7". One notable architectural change in these
new Pentium IIIs was the addition of a sixth physical layer to the
CPU. Previous Intel chips were composed of five physical layers.
#1: 0.18 micron fabrication.
biggest change was in the trace line width. That is the width of the
circuit lines etched into the semiconductor material. These are the
"wires" that carry current pulses through the CPU. Thinner wires
within the CPU means two things: 1) low power usage and therefore heat
production, and 2) smaller die size. The "die" size is
just the square area of the Pentium III chip itself.
The very first Pentium II was
based upon 0.35 micron wide circuitry. About a year ago, Intel
switched over to the newer 0.25 micron fabrication process, and added SIMD
instructions, giving us the Pentium III. Now comes and even bigger change
with the shift to the 28% smaller 0.18 micron fabrication process.
This is getting pretty darn small folks, we are talking only 180
nanometers wide. It's almost in the range of Nano Technology! The core
voltage on the Pentium II was 2.8 volts, while on the Pentium III "Katmai"
CPU it was 2.0 volts (2.05 for the PIII 600). The core voltage on
the "Coppermine" Pentium III is further reduced to 1.65
volts. This means substantially lower heat output, and better
The smaller die size for the
Coppermine means two important things for Intel and its customers.
1) More CPUs can be etched from a single blank "wafer", which
reduces Intel's costs (and hopefully ours eventually), and 2) there was
plenty of room left over for putting
more stuff on the processor die itself, which leads us to big change #2.
#2: 256Kb On-Die L2 cache.
Intel first came out with the Celeron, it had no L2 cache. All
processors have a small amount of built-in L1 cache (32Kb), but today's
applications require much more, and so a secondary, or Level 2 cache, is
added to just about all processors. The original Celeron was an
exception, and it suffered in both performance and sales. Intel
quickly added 128Kb of L2 cache onto the die of the Celeron, which means
it is actually part of the chip, rather than placed on a circuit board or
the motherboard. This is why this type of L2 cache is called
"on-die". The best part about on-die cache is that it runs
as part of the processor, at full processor speed. The
"off-die" L2 cache on the Pentium II was on a circuit board next
to the CPU, rather than in the CPU, and it could only run at half the
processor speed. So on-die L2 cache is twice as fast.
The results that Intel achieved
with the on-die L2 cache in the Celeron was better than expected.
In fact, the Celeron typically beat the more expensive Pentium II in many
benchmarks, due to it's faster L2 cache. This got Intel engineers
thinking about doing the same thing with the new Coppermine Pentium IIIs.
But 128Kbs of L2 cache was not enough for their new Flagship
product. Fortunately, the 0.18 micron process allowed them to cram
lots more circuit elements onto the same sized die. The majority of
the new die is actually dedicated to 256Kbs of CPU-speed L2 cache.
With twice as much L2 cache as the Celeron, the new Coppermine chips will
get better performance in cache intensive programs. The Pentium II
has 512Kbs of L2 cache, running at half processor speed, but unless you
are running a server, most standard applications will not need more than
256Kbs of L2 cache for optimal performance.
#3: L2 cache improvements (the ATC or
Advanced Transfer Cache).
has made some improvements to the design of the L2 cache as well.
First, the bus width on the Coppermine core's L2 cache was increased from
64 bits to 256 bits. This cache will operate faster than the Celeron's
cache, improving performance in cache intensive operations. They also
increased the L2 cache's associativity from 4-way to 8-way. These
improvements in the cache architecture will reduce the delay in retrieving
information from the cache. As long as the application running does
not make use of more than 256Kbs of cache, the new Coppermine chips will
outperform previous Pentium III processors running at the same clock
speed. In a way, this is a return to the concept of the Pentium Pro,
where L2 cache was on-die. But back then, with the substantially
coarser 0.35 micron etching process, the result was a very large and
expensive-to-produce chip. At 0.18 microns, an adequate 256Kb L2 cache is
easily incorporated into a much smaller die. Expect L2 caches to increase
to 512Kbs on-die in future Intel CPU's. Keep in mind that the Athalon
processor from AMD has 64Kbs 0f L1 cache, and 512Kbs of L2 cache
currently. But the Athalon's L2 cache is off-die, like with the original
Change #4: Advanced
System Buffering (ASB).
The final changes in the chip architecture are to improve communication
between the CPU and bus. There are several small memory locations
that buffer information traveling between the CPU and the system
bus. The number of these buffers was increased in the Coppermine
core. The "writeback" buffers were increased from 1 to 4, the
"fill" buffers were increased from 4 to 6, and the number of
"bus queue entries" was increased from 4 to 8. This should
facilitate the faster CPU-to-bus transfers that will occur on the new
133MHz front side bus.
Change #5: Increased
Front Side Bus Speed.
has finally increased the official bus speed on some of the new Coppermine
chips from 100MHz to 133MHz. Current PC-133-rated SDRAM will often
run at 150MHz, and so should the 133MHz Coppermine-based processors.
This means the 667MHz Pentium III should run well at 750MHz!
Right now, Intel has prices set
very high on the 700MHz and 733MHz CPUs, so your best bet is to steer away
from them until the next round of Intel price drops. The slower
speed Coppermine chips, on the other hand, are very reasonably
priced. The 500E is debuting at well under $300! This CPU will
almost certainly run at 665MHz with PC-133 SDRAM. We expect many of them
will go to 700MHz.
Keep in mind that not all new
Pentium III processors are based on the new 0.18 micron core. The
Pentium IIIs that are designated as "B" versions are based upon
the older 0.25 micron "Katmai" core, even though they are rated
for a 133MHz front side bus speed setting. The CPUs that are designated
"EB" are based upon the Coppermine core, and also have the
133MHz front side bus. We expect that the "E" versions
will have more head-room for bus frequency overclocking than the 133MHz
"EB" versions, but we won't know for sure until we get samples
- 0.25 micron process =>
0.18 micron process
- 512Kb slow L2 cache =>
256Kb fast L2 cache
- 64bit wide cache bus =>
256 bit wide cache bus
- 4-way associativity =>
- system buffers: 1-4-4 =>
system buffers: 4-6-8
- 100MHz bus speed =>
133MHz bus speed
While the new
"E" version Coppermine chips are listed at distributors and
resellers, don't expect that you will be able to get one right away.
They have not entered the supply channel in numbers that will get them to
many store shelves for at least one or two weeks. Expect shortages
through the end of the year.
This is a significantly
improved processor, especially if you plan on overclocking your
system. The lower power consumption and reduced heat production will
allow this processor to be overclocked to between 140MHz and 150MHz on the
front side bus, perhaps higher. We will post reviews of the
overclockability of these CPUs as soon as we can get them.