by March 1, 2001 0 comments

Servers usually have a much higher workload compared to the average home
computer because they serve multiple users at the same time. Hence, demands
placed on servers are such that they require specialized hardware to perform
efficiently. One critical component that determines their performance is the
server chipset. The chipset of a motherboard is a set of chips placed on it,
which control the flow of information between different components of the
system, like the processor, memory, and I/O devices. In this article, we’ll
take a look at this foundation of server motherboards.

Many times, a single processor is unable to satisfy the computation needs of
a high-load server. In such cases, the need for more processors arises.
Unfortunately, putting in multiple processors is not as easy as it sounds. The
chipset is assigned the difficult job of coordinating all these different
processors to reduce redundancy and take care of the integrity of the system.
This feature is called SMP, or Symmetric Multi Processing. This provides fast
processing by making multiple CPUs available to individual processes
simultaneously. SMP support is available in most chipsets targeted towards
server systems. For instance, the Intel 815 chipset, which is aimed at the
desktop, doesn’t have support for SMP, while the 840 supports two processors,
and the 440GX supports up to four processors.

Home computers currently use a 32-bit, 33 MHz PCI bus. This gives PCI devices
a total bandwidth of 132 MB/sec at their disposal. However, this can limit the
performance of certain cards. For instance, there are 64-bit network cards and
server management cards that require higher bandwidth to give peak performance.
So server chipsets include support for 64-bit and 66 MHz PCI bus, which
effectively quadruples the bandwidth available. The Samurai chipset from Micron,
for example, supports this feature.

Hard-disk data transfer rates can also be a severe bottleneck in the
performance of a server. Almost all servers use SCSI hard drives, which provide
much higher bandwidth compared to IDE drives. Lately the trend has been to
include high-speed SCSI controllers on the motherboard itself to eradicate the
need of putting in PCI cards to perform the same function. The latest SCSI
standard, Ultra 160 supports data transfer speeds up to 160 MB/sec.

Before the processor can execute a process, it needs to be loaded into the
memory. If the amount of memory is not enough, processes are continuously
switched between the memory and hard drive to make room for new processes. This
can greatly reduce performance. So most people try to cram in as much RAM as
possible into the system. However, the amount of memory one can put into a
system is limited by the chipset. Whereas most home computers are limited to a
maximum of 512 MB, it is not uncommon to see support for gigabytes of memory in
server systems. The 440GX, for example, supports up to 2 GB of memory.

Finally, something that is generally better in a home computer compared to
servers– sound and video. Since what generally matters more in a server is the
number of people you can host, rather than the number of frames it can pump out
Quake III, people stick to relatively old and trusted equipment here. Most
server boards therefore come with on-board video.

Anuj Jain

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