Louis Lagendijk louis@lagendijk.xs4all.nl wrote:
look for DMA settings for the drive. turning DMA off could help
Of course, that turns off DMA for the _entire_ channel.
If you're shunting the ATA channel into PIO (e.g., for an ATAPI device like a CD-ROM), back to DMA (e.g., for an ATA device like a fixed disk), then back to PIO, etc..., that's the best way to absolutely destroy performance on your ATA channel.
Remember what ATA is -- it's a "dumb," 16-bit [PC/]AT Attachment (ATA) channel with integrated drive electronics (IDE) on the end-devices themselves. If the master IDE and slave IDE are radically different, they will constantly reset the ATA bus when each takes control in the best case, or have grave compatibility issues in the worst case.
When you use your CPU to do Programmed I/O (PIO) -- the IDE isn't as much of an issue. But when the IDE is not bothering the CPU to do Direct Memory Access (DMA), that's a serious concern. Especially if one device is doing DMA, and then the other device is doing PIO.
As this does not seem the cause of the problem, I would tend to suspect the cable. Is the cable Ultra-DMA capable (high density 80 wires)?
The majority of ATA device IDEs autodetect the type of cable. During the post, if they don't detect the extra 40 conductors (80 total), they will reduce signaling to 8MHz maximum. I.e., - UltraDMA mode 2 = 16-bit x 8MHz DDR (33MBps) - PIO Mode 4 = 16-bit x 8MHz (16MBps)
In any case, replace it with an Ultra-DMA capable cable
Hate to be anal, but that's a misnomer and an incorrect description.
It is commonly referred to as an Ultra66/100/133 capable cable.
Standard 40 conductors are capable of 8MHz, including the 4.17, 5.5 and 8.33MHz DDR signaling (8.3, 11 and 16.6MHz, effective) used in UltraDMA modes 0 (16MBps), 1 (22MBps) and 2 (33MBps) -- commonly and collectively referred to as Ultra33.
It's only when higher signals are used for UltraDMA modes 3 (50MBps), 4 (66MBps), 5 (100MBps) and 6 (133MBps) that you need the 80 conductor. I don't know what the signaling is, but I assume it is 12.5 (3), 16 (4), 25 (5) and 33 (6) MHz DDR, respectively. I could be mistaken on Ultra133, and maybe 133MBps is 16MHz QDR.