Hardware factors that influence performance
Your system's hardware has the greatest influence
on its performance. It is the ultimate limiting
factor on how fast a process will run
before it has to start sharing what is available
with the operating system and other user processes.
can require you to add hardware
or upgrade existing hardware
if a system's physical subsystems are unbalanced in power,
or insufficiently powerful to satisfy the demands being put on them.
There may come a time when, despite your best efforts,
you cannot please enough people enough of the time
with the hardware resources at your disposal.
If so, you will have to go and buy some more hardware.
This is one reason why monitoring and recording
your system's performance is important
if you are not the person spending the money.
With the information that you have gathered,
you can make a strong case for upgrading your system.
It is important to balance the power
of your computer's subsystems with each other;
the power of the CPU(s)
is not enough in itself.
If the other subsystems are slow
relative to the available processing power,
they will act to constrain it.
If they are more powerful,
you have possibly overspent,
although you should be able to upgrade processing power
without much extra expenditure.
There are many hardware factors
that can limit the overall system performance:
On multiprocessor machines,
the following considerations also become important:
The speed and width of the system's address and data buses.
The model, clock speed, and the size
of the internal level-one (L1) memory cache
of the system's CPU or CPUs.
The size of the level-two (L2) cache memory
which is external to the CPU.
This should be capable of working with all of
The amount of memory, the width of its data path, and its access time.
The time that the CPU has to wait
for memory to be accessed limits its performance.
The speed and width of a SCSI bus
controlled by a host adapter.
The width of the data path on peripheral controller cards (32, 16, or 8-bit).
Whether controllers have built-in cache.
This is particularly important for disk and network controllers.
Access time for hard disks.
Whether intelligent or dumb serial cards are used;
intelligent cards offload much of the work
that would otherwise be performed by the CPU.
Write-back L2 cache (for instructions and data)
with cache coherency on each CPU
to reduce the number of accesses to main memory.
This has the benefit of improving CPU performance
as well as improving general system performance
by reducing contention for the system bus.
Support for fully
to allow any CPU to service
from I/O devices such as network and disk controllers.
The memory and I/O subsystems
must be as fast as possible
to keep up with the demands of the enhanced CPU performance.
Use of intelligent peripheral controllers is particularly desirable.
Software factors that influence performance
What determines performance
© 2003 Caldera International, Inc. All rights reserved.
SCO OpenServer Release 5.0.7 -- 11 February 2003