The move to multicore processors is boosting system performance to levels that
have never been seen outside of highend SMP systems. Better yet, this increase
in processing power is happening without the huge increases in price and power
requirements that moving to traditional SMP systems entails. For SQL Server
systems, added processing power can mean increased levels of system performance
as well as higher levels of scalability. Let's take a look at some of the latest
developments in the dual-core and quad-core processors that Intel and AMD are
bringing to market and see what this technology means for your SQL Server environment.
Dual-Core Performance
When manufacturers became unable to improve processing power simply by boosting
processor speed, both Intel and AMD realized that the easiest path to more power
was through parallelism.
The ever-shrinking size of processors made it possible to produce dual-core
chips, which combine two processors on a single die. An added benefit of dual-core
chips is that they nearly double the available CPU power while using the same
power envelope (i.e., the same wattage requirements) as a single processor.
Figure 1 shows the results of running the
SAP Sales and Distribution (SD) Users benchmark on AMD Opteron systems that
were identically configured except for the processor. The dual-core Opteron
875 provided a 74 percent increase in performance over the single-core Opteron
852.
Dual-Core Design
In 2005, Intel became the first to enter the dual-core market with the release
of the Pentium D processor, built using the Intel NetBurst microarchitecture.
In January 2006, Intel switched to the Core microarchitecture, which uses a
shorter instruction pipeline than does NetBurst, letting processors execute
substantially more instructions per clock cycle and achieve higher levels of
performance even though they run at a lower clock frequency than earlier Intel
CPUs.
The shared front-side bus technology of Intel's dual-core design gives each
processor half the bandwidth of the front-side bus. Memory and I/O access operations
also share the bus, making the bus speed a critical factor in overall system
performance. Intel's latest dual-core processor, the Core 2 Duo, is built using
65 nanometer (nm) technology and integrates both cores on a single die. Each
core has 64KB of dedicated L1 cache—a 32KB instruction cache and a 32KB
data cache—and both cores share a 4MB L2 cache. The Core 2 Duo has a
new power-saving design and a 1066MHz front-side bus. It also supports Intel
Extended Memory 64 Technology (EM64T), Intel's 64-bit memory extension, and
Intel Virtualization Technology (Intel VT).
Following Intel's lead, AMD introduced the 64-bit dual-core Athlon 64 X2, and
later the dual-core Opteron. In AMD's Direct Connect Architecture, each CPU
has an integrated memory controller and the HyperTransport bus runs at 1GHz
and allows an 8GBps direct connection between the CPUs, I/O, and memory. The
AMD Opteron 875 dual-core processor has an L1 cache with 64KB for instructions
and 64KB for data, plus a 1MB L2 cache. AMD manufactures its dual-core line
using 90nm technology. In February 2007, AMD released new dual-core Opterons
that run at clock rates up to 2.8GHz and provide greater power efficiency than
earlier models.
Quad-Core Performance
The jump from dual-core to quad-core processors delivered another big performance
boost. Figure 2 shows the results of some
benchmark tests on the Quad-Core Intel Xeon processor X3220 and the Dual-Core
Intel Xeon processor 3070. The SPECfp_rate_base2000 benchmark measures floating
point performance, the SPECint_rate_base2000 measures integer performance, and
the LINPAC measures billions of floating point operations per second. SPECjbb2005
is a Webbased Java benchmark that simulates an order entry system. Although
the X3220 runs at a slightly slower clock rate, it outperforms the 3070 in all
the benchmarks.
Quad-Core Design
With the release of the Quad-Core Intel Xeon 5300 series in November 2006, Intel
is the clear leader in the quad-core race. AMD won't have an entry until mid
2007, when it will introduce a quad-core chip code-named Barcelona. However,
Intel's and AMD's quad-core designs are significantly different.
Intel's quad-core design puts two dualcore processors onto a single chip. In other
words, instead of being a "native" quadcore processor, Intel's quad-core Xeon is
actually a dual dual-core chip. Although
this architecture enabled Intel to beat
AMD to market, the design isn't optimal.
When processors that are on separate
cores exchange data, the data must be
sent over the front-side bus and through
the memory controller, which isn't the
most efficient mechanism. In addition, as
with previous Intel designs, this approach
makes the overall system speed dependent
on the speed of the front-side bus. Despite
these drawbacks, the additional CPUs and
improvements in the Intel Core microarchitecture make Intel's quad-core chips
the fastest x64-compatible processors available today.
In contrast, AMD's upcoming Barcelona mounts four independent CPUs on one die.
AMD's quad-core chip will utilize the Direct Connect Architecture. Barcelona
will be built using a 65nm process technology and will have versions that utilize
a 68-, 95-, or 120-watt power envelope. This model enables all four cores to
act independently, leading to more efficient power consumption because each
core can adjust its frequency according to the workload.
Among other important enhancements, the Barcelona design sports 128-bit floatingpoint
processing and a new 2MB L3 cache that's shared by all the processors. Because
each processor performs more work per clock cycle, an estimated 15 percent efficiency
improvement per core results in an improvement in processor performance of about
40 percent. The AMD quad-design is socket-compatible with existing Socket F
dual-core processors. Consequently, existing dual-core systems built with the
AMD Socket F can be upgraded to quad-core by performing a CPU swap and then
upgrading the BIOS. The scalability of the Barcelona should also be greater
than that of Intel's quad-core CPU. Each core on Barcelona's quadcore die could
theoretically be upgraded to a dual-core chip in the future, essentially enabling
a design that incorporates four dual-core CPUs on one quad-core die.
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