Uwe Hermann | A slightly paranoid Debian developer

Sometimes funny things happen. I spent several hours yesterday, trying to figure out why my laptop is responding so darned slow. I suspected it had something to do with the hard drive and I found out quite quickly that (U)DMA was disabled, hence the CPU had to do all the work. OK, no problem, I'll just do a hdparm -c1 -d1 /dev/hda and everything will be fine. Or so I thought.

What I got was this:

setting using_dma to 1 (on)
HDIO_SET_DMA failed: Operation not permitted
using_dma = 0 (off)

Which means DMA could not be enabled. I noticed an error message in the output of dmesg which seemed related: ide0: Speed warnings UDMA 3/4/5 is not functional. Some people had the same problems because they were missing the correct option in the kernel (mine is CONFIG_BLK_DEV_PIIX), but that was not my problem. After a few hours of googling and 6 or 7 kernel recompiles, I gave up and went to bed.

Now to the funny part: Today, John Choffee posted a comment about bashpodder in my blog. Curious as I am, I also visited his blog and in his "LinkFeed" box a tiny entry caught my attention: [PATCH] ich6m-pciid-piix.patch. Now guess what this patch (for Linux 2.6) does. It adds support for my specific type of IDE/(S)ATA controller, the "Intel Corporation 82801FBM (ICH6M)". Patch, recompile kernel, reboot, hdparm -c1 -d1 /dev/hda, bingo!

Here's the output of hdparm -tT /dev/hda:

Before the patch:

Timing cached reads: 2468 MB in 2.00 seconds = 1232.95 MB/sec
Timing buffered disk reads: 8 MB in 3.84 seconds = 2.08 MB/sec


After the patch:

Timing cached reads: 2624 MB in 2.00 seconds = 1312.20 MB/sec
Timing buffered disk reads: 88 MB in 3.00 seconds = 29.33 MB/sec


Thanks John, you're my personal hero today.

Update 2006-03-01: The URL for the patch is broken. This one works.