Tweaking Optimizing Windows.pdf - GEGeek

two options. Either you can use a PCI video card or a different chipset. At 160MHz, the AGP bus is running 107MHz, 62% over
spec, however the PCI bus is running at 40MHz (only 21% over spec). You can also look at motherboards which are designed for
the 133MHz FSB and thus support a 1/2 AGP divider. These include boards based around the Intel i815 chipset, the VIA Apollo Pro
133 and 133a chipsets, or the i820 (uses DRDRAM). With a 1/2 AGP divider, the AGP is running only 80MHz while the FSB runs at
160MHz and should be well within the tolerances of most cards. There has been good success at 166MHz FSB with the i815 chipset,
which is probably your best bet for high FSB settings. There are reports of both the BX chipset and the i815 chipset reaching
220MHz FSB using special cooling and modified motherboards.
In addition, certain FSB speeds are harder to reach than others. For example, the 83MHz FSB speed will not run reliably on many
systems, even where the same system might be able to run a 95 or 100MHz setting. This all depends on what speed the
motherboard is set to change the AGP and PCI dividers and how sensitive the system is to the higher bus speeds. PCI Speeds of
greater than 40-42MHz generally cause problems. Timing sensitive devices such as network cards, SCSI cards and video input
devices sometimes have trouble at even lower speeds. AGP speeds of 80MHz and above cause problems on many older cards,
however newer cards can often run up to around 90MHz. Another measure to stabilize a card is to reduce the bus interface to AGP
1x, disable sidebanding or disable fast writes these will help you get a little higher speed, but it is best to just accept the speed that
your system runs with these features enable. One other extreme method of squeezing out a few more MHz is to decrease the "AGP
Aperture" to minimum (usually 4MB). By basically cutting off 95% of the communication between the main memory and AGP card,
this method will cause your card to run EXTREMELY poorly in 3D applications, however will allow you to brag to your friends that
you have the highest MHz rating!! *big grin* Exact dividing points depend on your motherboard and are sometimes adjustable.
Pushing the limits of agp and pci clock
How does overclocking or adjusting the FSB effect other components, such as video cards, sound cards, and hard drives? Greatly.
Make sure if you're running at 100 MHz FSB, you try to set the PCI clock to 1/3. For anything significantly higher, try to set the PCI
clock to 1/4 (if available). If the PCI bus clock reaches about 43 MHz or higher (remember, 33 MHz default), it could possibly fry the
contents of your hard drive (the data, that is). Also it could make items such as sound cards and network cards not function
properly.
On the same note, AGP clock shouldn't be set much higher than 66 MHz (default). If you set the bus speed to 100 or higher, set the
multiplier to 2/3 or lower (if available). Higher AGP clocks will not help performance, but can harm stability, and possibly kill an AGP
card over long periods of time.
FSB speedagp divider pci divider
50-79MHz1/11/279-83MHz1/1 or 2/31/2 or 1/383-117MHz2/31/3117-124MHz2/3 or 1/21/3 or 1/4124MHz+2/3 or
1/2*1/4*Depending on chipset Note: many motherboards depend on the CPU's request for either 100 or 133 FSB to determine
the AGP divider. Thus, on a CPU that normally runs at 100MHz the AGP divider will be 2/3, regardless of the support for a 1/2 AGP
divider. In this case, check your manual for a "FSB override", "sel 100/133" or "AGP divider" jumper or switch, or use a Slocket that
has such a jumper (such as Iwill's Slocket II).
Memory speed considerations
Today, the great majority of people run SDRAM memory. Old 72-pin SIMMS with an EDO or FP format are now very outdated and
never found in 'modern' systems. The newest Direct Rambus DRAM is is too expensive for the normal desktop system. Standard
SDRAM is found in three varieties, separated by their maximum speed capability. Original SDRAM runs at 66MHz and is sometimes
called PC66. Newer memory speeds are PC100 and PC133. There are also companies that sell a PC150 memory, however this is not
an officially recognized format. DDR (double data rate) SDRAM is just beginning to enter the mainstream as a SDRAM 'replacement'.
It has been used for several years on graphics cards and in specialized applications however this is the first it will be available for
commercial, all purpose use. The AMD 760 was the first chipset to introduce DDR SDRAM support. It was announced October 30th,
2000 and represents the next step in the evolution of the x86 architecture. It may very well replace the failing DRDRAM standard
being pushed by Rambus. Generally, if you are running over 100MHz FSB it is best to use PC133 memory. While some of the
highest quality PC100 memory has been shown to run over 145MHz, you will have much more consistent results with PC133
memory. SDRAM chip speed is measured by its refresh rate and is expressed in nanoseconds (ns). Standard (PC66) SDRAM is
usually rated at 12ns. PC100 memory must be rated with 10ns or faster speed, however most modern, high quality PC100 memory
is rated at 8ns. PC133 memory must be rated at 7.5ns or faster and has stricter tolerances than PC100 for layout and signal
interference in the module itself. When aiming at 133MHz or above, you should always try to use PC133. While some of the best
PC100 memory has been tested beyond 145MHz, most modules will not run much above 124-133MHz and some will barely do
112MHz. PC133 modules are guaranteed to run at least 133MHz and thus most will run faster.
Cas, ras and memory timings
SDRAM is physically organized in rows and columns of memory addresses. CAS stands for "column access strobe" and refers to the
speed the column strobe can be flashed. There are generally two other timings which can be adjusted, called RAS (row access
strobe) and CAS-to-RAS delay. Decreasing the timings leads to higher performance, however increased timings can result in higher
a tolerance for overclocking. A CAS delay of 2 cycles is generally referred to as CAS2 and is the fastest rating of current generation
memory. A CAS3 rating is about 2-3% slower and memory that is only rated to CAS3 timings should be avoided while overclocking
because it offers slightly less leeway in overclocking. The CAS timing is the most critical of the group, however RAS and CAS to RAS
can also be adjusted. Often these memory timings are given together, written as 2-2-2 or 3-3-3 or any other combination of
timings. Generally, 2-2-2 yields the highest performance and 3-3-3 the slowest. A timing of 3-2-2 is a common setting for systems
where CAS2 is slightly unstable as it is a good compromise between performance and clock speed. Read the PC133 SDRAM Article
for more info on which memory is best at what speeds and how you can determine ns ratings on your memory. The newest
chipsets from both Intel and VIA, including the VIA Apollo 133(a) series and the i815 support "asynchronous" memory operation.
This simply means that the memory clock can be adjusted independently from the FSB speed. The speed is generally adjusted in
coarse increments of around 33MHz. It is often expressed as FSB+33 and FSB-33 or FSB+PCI and FSB-PCI. The FSB+/-PCI is a
more accurate description because the memory clock is usually set using the PCI speed. Basically it means that you take the FSB
speed and subtract/add the PCI speed. This comes in handy in several situations. First, when running extremely high FSB settings
such as 155-166MHz FSB memory can be difficult if not impossible to find. Adjusting the memory to a slower speed can allow slower
memory to run on a very high FSB. Also, it can be useful to increase system performance by running a higher memory speed while
still using a slower FSB speed. Running a 100MHz FSB, you could set your memory to run at 133MHz, thus increasing system
performance by 1-3%.