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
- CPUID Maximum Value Limit from The Tech ARP BIOS Guide!
- Bank Swizzle Mode from The Tech ARP BIOS Guide
- Master Priority Rotation from The Tech ARP BIOS Guide!
- RW Queue Bypass from The Tech ARP BIOS Guide
- AGP Capability from The Tech ARP BIOS Guide
- PCI Clock Synchronization Mode – The Tech ARP BIOS Guide
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