When StorageReview.com initially began tests on our first roundup of ATA drives, the 6.4GB UDMAs, we installed Intel's PIIX v3.01 drivers to control the PIIX4 chip found on the Abit LX6 motherboard. Intel's drivers were notorious for inflating results in benchmarks with no corresponding real-world performance gain, including ZDBOp's WinBench 97. However, ZD took steps to correct the problems; WinBench 98 is no longer susceptible to the same limitations. After the benchmarks were complete, reports started to surface (starting at Dan Chadwick's tweakit.com) that the PIIX drivers did nothing to help performance while in fact grossly raising CPU utilization during disk reads over the stock bus master drivers found in Windows 95 OSR2. Though it was overshadowed by the introduction of FAT32, IDE Bus Mastering was a substantial storage-related upgrade included the new revision of Win95. Many were already in the habit of using the PIIX drivers, though, and did not bother to compare what OSR 2 offered vs Intel's drivers.

To obtain the benchmark results tabulated on the left, Storage Review used a plain installation of Windows 95 OSR 2.1. We then patched the default installation with Intel's 82371xB INF Update (also known as setupex.exe, needed to recognize the newer 430TX and 440LX chipsets) and Microsoft's Removable IDE Device Patch. Finally, under the test drive's entry in System Properties' Device Manager we checked the "DMA" box, enabling the OSR2 Bus Mastering drivers. The PIIX results were obtained by taking this configuration and also installing Intel's PIIX v3.01 drivers. IBM's Deskstar 5 6.4GB drive, posting the highest scores of all the ATA drives tested, was selected as the test drive for Bus Mastering effects.

The benchmark figures indicate that installing the PIIX drivers results in a slight but negligible hit (1.2% decrease) in WinBench's Business Disk WinMark 98 score. The reverse is true when looking at the High-End WinMark 98, there is a slight increase (2.8%). Disk/Read Random Access and Transfer Rates remained the same. However, Disk/Read CPU Utilization jumps an astounding 677%, up to 35.2% from 5.2%.

It is often said by SCSI proponents that ATA drives cannot touch the miniscule CPU utilization posted by SCSI drives. This is simply untrue. The perception is likely perpetuated simply because most run tests using PIIX vs SCSI instead of OSR2 vs SCSI. While SCSI still holds benefits over ATA devices in many areas, CPU utilization is not one of them. Its important to note that to achieve the low CPU utilization scores (along with an increase in the sequential data transfer rates) that the drive's individual DMA box must be enabled. Leaving the box unchecked will result in CPU Utilization scores in the 80-90% range.

Users still running the original release of Windows 95 still benefit from installing Intel's PIIX drivers. However, those running OSR2 should simply stick with the built-in Bus Mastering drivers. OSR2 not only offers more efficient space utilization with FAT32, it brings SCSI-like CPU utilization levels to the table.