6. Onboard UDMA interfaces

These are UDMA­capable drive interfaces built into motherboards. They use the standard IDE I/O ports and so are fully usable at the slower non­UDMA speeds on an unpatched 2.0.x kernel such as are used when installing Linux. Thus they should not cause any difficulties during installation, and patching for UDMA speed is a welcome luxury instead of a necessary step. Some UDMA support is in the latest 2.0.x kernels I believe, and is built into current 2.2.x kernels for the Intel chipsets.

6.1 Intel FX, HX, VX, TX, LX, and BX

Thanks again to Gadi for this info:

Bus mastering DMA support for the Intel TX chipset is available in 2.0.31
and above.

In older kernels (such as Slackware 3.4's 2.0.30), the interface will be used in the slower EIDE mode. In either case the interface will be automatically detected by the kernel and you should have no trouble using it.

Full UDMA mode 2 support for these chipsets is included in 2.2.x kernels and the unified IDE patch; see Unified IDE.

6.2 The VIA VP2 and Related Chipsets

This interface also can be autodetected and used in EIDE mode by an unpatched kernel, but if you have one of these, you will want to grab a patch so you can get faster throughput and do away with annoying "unkown PCI device" messages.

One is available at http://www.ipass.net/~prefect/; it is designed for the VIA VP2/97 chipset, found on FIC's PA-2007 and PA-2011 motherboards, but may work on related chipsets. It has been reported that it functions on the newer VIA VP3 chipset, your mileage may vary.

Note that this patch only supports Bus Mastering mode, not full UDMA mode, but it's still better than plain-vanilla EIDE mode. Follow the directions at the patch's site for enabling BMDMA mode.

There is another patch that supports full UDMA mode at http://www.pyreneesweb.com/Udma/udma.html, designed for the VIA VT82C586B, and it ought to work on the VP2, VP3, VPX, P6 and AGP Apollo chipsets. Follow the directions for installation and UDMA enabling there, but it is recommended that you back up any data you want to keep, as there are potential problems with incompatible motherboards. But, if it does work, it should work without problems.

Note that the VP1 chipset is not known to work with these patches, but is supported by the Unified IDE patch.

6.3 TX Pro and other ``Pro'' boards

UDMA is not currently supported for the TX Pro motherboards. They are not the same as a TX mobo, and apparently misreport their DMA capabilities hence the problem. Someone is working on this I hear, so a patch may appear some time in the future but not yet.

6.4 HPT 366

This chipset is on the popular Abit BP-6 motherboard and others, and provides UDMA mode 4 66MB/s support on two generals, generally in addition to two other mode 2 33MB/s channels. It is supported by the current unified IDE code but not in any current release kernels. Installation thus may require workarounds similar to the Promise Ultra33 did on older 2.0.x kernels.