Tag Archives: DMA

IDE Bus Master Support from The Tech ARP BIOS Guide!

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IDE Bus Master Support

Common Options : Enabled, Disabled

 

Quick Review of IDE Bus Master Support

The IDE Bus Master Support BIOS feature is a misnomer since it doesn’t actually control the bus mastering ability of the onboard IDE controller.

It is actually a toggle for the built-in driver that allows the onboard IDE controller to perform DMA (Direct Memory Access) transfers.

When this BIOS feature is enabled, the BIOS loads up the 16-bit busmastering driver for the onboard IDE controller. This allows the IDE controller to transfer data via DMA, resulting in greatly improved transfer rates and lower CPU utilization in real mode DOS and during the loading of other operating systems.

When this BIOS feature is disabled, the BIOS will not load up the 16-bit busmastering driver for the onboard IDE controller. The IDE controller will then transfer data via PIO.

Therefore, it is recommended that you enable IDE Bus Master Support. This greatly improves the IDE transfer rate and reduces the CPU utilization during the booting process or when you are using real mode DOS. Users of DOS-based disk utilities like Norton Ghost can expect to benefit a lot from this feature.

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Details of IDE Bus Master Support

The IDE Bus Master Support BIOS feature is a misnomer since it doesn’t actually control the bus mastering ability of the onboard IDE controller.

It is actually a toggle for the built-in driver that allows the onboard IDE controller to perform DMA (Direct Memory Access) transfers.

DMA transfer modes allow IDE devices to transfer large amounts of data from the hard disk to the system memory and vice versa with minimal processor intervention.

It differs from the older and processor-intensive PIO transfer modes by offloading the task of data transfer from the processor to the chipset.

Previously, this feature is only available after an operating system that supports DMA transfers (via the appropriate device driver) is loaded up.

But now, many BIOS come with a built-in 16-bit driver that allows DMA transfers. This allows the onboard IDE controller to perform DMA transfers even before the operating system is loaded up!

When this BIOS feature is enabled, the BIOS loads up the 16-bit busmastering driver for the onboard IDE controller. This allows the IDE controller to transfer data via DMA, resulting in greatly improved transfer rates and lower CPU utilization in real mode DOS and during the loading of other operating systems.

When this BIOS feature is disabled, the BIOS will not load up the 16-bit busmastering driver for the onboard IDE controller. The IDE controller will then transfer data via PIO.

Therefore, it is recommended that you enable IDE Bus Master Support. This greatly improves the IDE transfer rate and reduces the CPU utilization during the booting process or when you are using real mode DOS. Users of DOS-based disk utilities like Norton Ghost can expect to benefit a lot from this feature.

Please note that since current operating systems (i.e. Windows XP) load up their own 32-bit busmastering driver, this feature has no effect once such an operating system loads up. Still, it is recommended that you enable this feature to improve performance prior to the loading of the operating system’s own driver.

 

Recommended Reading

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ECP Mode Use DMA – The BIOS Optimization Guide

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ECP Mode Use DMA

Common Options : Channel 1, Channel 3

 

Quick Review

This BIOS feature determines which DMA channel the parallel port should use when it is in ECP mode.

The ECP mode uses the DMA protocol to achieve data transfer rates of up to 2.5 Mbits/s and provides symmetric bidirectional communications. For all this, it requires the use of a DMA channel.

By default, the parallel port uses DMA Channel 3 when it is in ECP mode. This works fine in most situations.

This feature was provided just in case one of your add-on cards requires the use of DMA Channel 3. In such a case, you can use this BIOS feature to force the parallel port to use the alternate DMA Channel 1.

Please note that there is no performance advantage in choosing DMA Channel 3 over DMA Channel 1 or vice versa. As long as either Channel 3 or Channel 1 is available for your parallel port to use, the parallel port will be able to function properly in ECP mode.

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Details

This BIOS feature is usually found under the Parallel Port Mode feature. It is slaved to the ECP (Extended Capabilities Port) option. Therefore, if you do not enable either ECP or ECP+EPP, this feature will disappear from the screen or appear grayed out.

This BIOS feature determines which DMA channel the parallel port should use when it is in ECP mode.

The ECP mode uses the DMA protocol to achieve data transfer rates of up to 2.5 Mbits/s and provides symmetric bidirectional communications. For all this, it requires the use of a DMA channel.

By default, the parallel port uses DMA Channel 3 when it is in ECP mode. This works fine in most situations.

This feature was provided just in case one of your add-on cards requires the use of DMA Channel 3. In such a case, you can use this BIOS feature to force the parallel port to use the alternate DMA Channel 1.

Please note that there is no performance advantage in choosing DMA Channel 3 over DMA Channel 1 or vice versa. As long as either Channel 3 or Channel 1 is available for your parallel port to use, the parallel port will be able to function properly in ECP mode.

 

Support Tech ARP!

If you like our work, you can help support our work by visiting our sponsors, participating in the Tech ARP Forums, or even donating to our fund. Any help you can render is greatly appreciated!