Linux Pentium III Chipset Comparison

Disk Performance: Configuration and Issues

As mentioned before, one of the reasons we chose to use a newer Linux kernel (2.4.0-test11) instead of the stable releases (2.2.xx) was that it contained better support for ATA/66 and ATA/100 transfer modes. Some of this work is available for older kernels in the form of backported patches, but we wanted it as good as we could get.

Linux kernels have actually generally lagged behind in IDE support more so than in other areas for a while now. There was a time in which SCSI was considered the way to go. Linux then gained DMA transfer capabilities and, in more recent times, support for the newer burst transfer modes. We were able to configure the kernel to run at ATA/100 on the Intel 815 chipset, ATA/66 on the VIA Apollo Pro 133a and ATA/33 on the venerable Intel BX chipset. The hdparm parameters used for the Intel 815 chipset were -c1 -d1 -m16 -X69 -k1, which enables 32bit transfers, DMA transfers, 16 block multisector transfers, UltraDMA mode5, and sets the keep flag (keep settings after an IDE reset). The VIA used -X68 instead of -X69, indicating UltraDMA mode4 (ATA/66). The Intel BX chipset used -X66 for UltraDMA mode2 or ATA/33 support.

Remember that these tests are designed to show disk performance that can be obtained with large block data transfers. This does not reflect average performance, but rather a general theoretical limit. Further, the performance listed in the ATA/XX specs is not meant to be sustained, but rather burst transfer rates. Many benchmark apps are designed to fit within this burst range to achieve the highest possible bandwidth available by the chipset. These benchmarks don't appear to be quite so optimized. Further, it is possible that the Linux kernel in its architecture or implementation restricts throughput to lesser levels than listed in the high speed DMA modes.

All tests were conducted on an IBM 75GXP. This drive supports fully ATA/100 and has a 2MB buffer, making it one of the best performing IDE drives available today.