Options : Enabled, Disabled

This feature forces the chipset to use the 4-bank SDRAM interleave mode. For better performance, enable this feature but you have to have at least 4 banks of SDRAM in order to use this feature. Note that banks of SDRAM are different from the number of DIMMs you use. That's because each SDRAM DIMM comprises of one or more banks of SDRAM that can be accessed simultaneously.

Normally, 2-bank SDRAM DIMMs use 16Mbit SDRAM chips and are usually 32MB or less in size. 4-bank SDRAM DIMMs, on the other hand, usually use 64Mbit SDRAM chips though the SDRAM density may be up to 256Mbit per chip. All SDRAM DIMMs of at least 64MB in size or greater are 4-banked in nature. 

For more information, check out SDRAM Bank Interleave.

Options : 0 - 255

This feature controls how long each PCI device can hold the bus before another takes over. The larger the value, the longer the PCI device can retain control of the bus. As each access to the bus comes with an initial delay before any transaction can be made, low values for the PCI Latency Timer will reduce the effective PCI bandwidth while higher values improve it.

On the other hand, while increasing the value lets each PCI device access the bus longer, the response time of those PCI devices suffers as a result. That means every PCI device will have to wait longer before they can get access to the bus but when they do get access, they can conduct their transactions for a longer time.

Normally, the PCI Latency Timer is set to 32 cycles. For better PCI performance, a larger value should be used. Try increasing it to 64 cycles or even 128 cycles. Some PCI devices may not agree with longer latency times so if you start facing problems like stuttering sound or a less responsive system, reduce the latency. Higher values will actually reduce performance as too much time may be allocated to each PCI device to the disadvantage of other devices on the bus.

Options : Auto, Manual

This BIOS function is similar to AGP Driving Control, which allows you to adjust the control of the AGP driving force. It is usually set to Auto by default, thereby allowing the chipset to assume control and automatically adjust the AGP driving force to suit the installed AGP card.

However, for troubleshooting or overclocking purposes, you can set the AGP 4X Drive Strength to manual so that you can select the AGP Drive Strength values (see below) you want. Unlike AGP Driving Control, this function usually comes with two to four different controls for its drive strength. In case you forgot, AGP Driving Control only comes with a single control for AGP drive strength.

AGP Drive Strength P or N Ctrl

Options : 0 to F (Hex number)

These options are slaved to the AGP 4X Drive Strength BIOS function. If you set the AGP 4X Drive Strength to Auto, then the values you set here won't have any effect. In order for these BIOS options to work, you need to set the AGP 4X Drive Strength to Manual.

The AGP Drive Strength P Ctrl and N Ctrl options work hand-in-hand to determine the signal strength of the AGP bus. The AGP Drive Strength is represented by Hex values from 00 to FF. The higher the value, the stronger the signal.

As you can see, P Ctrl only has values from 0 to F. Therefore, it can only set the first part of the actual AGP Drive Strength value. The N Ctrl function also has values from 0 to F and thus, provides the remaining part of the actual AGP Drive Strength value. Confused? Here's the gist :-

The AGP Drive Strength is controlled by two Hex values (xx) ranging from 00 to FF (0 to 255 in decimal values). P Ctrl controls the first Hex value (Xx) while N Ctrl controls the second Hex value (xX). Together, they set the AGP Drive Strength value. For example, if you want to set an AGP Drive Strength of D4 (212), you will have to set P Ctrl to D and N Ctrl to 4.

By default, the AGP Drive Strength is set to C5 (197) but if you are using an AGP card based on the NVIDIA GeForce2 line of GPUs, then it's recommended that you set the AGP Driving Value to the higher value of EA (234).

Due to the nature of this BIOS option, it's possible to use it as an aid in overclocking the AGP bus. The AGP bus is sensitive to overclocking, especially in AGP4X mode and with sidebanding enabled. As such, a higher AGP Driving Value may be just what you need to overclock the AGP higher than normally possible. By raising the signal strength of the AGP bus, you can improve its stability at overclocked speeds.

But be very, very circumspect when you increase the AGP Drive Strength on an overclocked AGP bus as your AGP card may be irreversibly damaged in the process!

BTW, contrary to some reports, increasing the AGP Driving Value won't improve the performance of the AGP bus. It is not a performance enhancing option so you shouldn't increase the value unless you need to.

PCI Master Read Caching

Options : Enabled, Disabled

Just like Video RAM Cacheable, this feature may actually hinder performance although it was designed to improve performance. How is that so?

If this feature is enabled, the CPU L2 cache will be used to cache PCI master reads. This boosts the performance of PCI masters. However, it uses up some of the CPU's L2 cache. That's why ASUS recommends that only those using AMD Athlons should enable this feature. Duron users should disable this feature because its small L2 cache will not be able to cache the PCI reads without a massive hit to memory bandwidth.

However, it's questionable that even Athlon systems will really benefit from this feature. For one thing, the Athlon doesn't have so much L2 cache that using it to boost PCI master performance won't detrimentally affect its performance. And just like the Video RAM Cacheable feature, it involves two-way use of the CPU bus (the EV6 bus in this case), which reduces its performance.

So, does the boost in PCI master performance justify the loss in CPU and memory performance? Although the final word is still in the air, I recommend disabling this feature. IMHO, the use of precious L2 cache to cache PCI masters are just not worth the potential benefit in PCI performance.