Is libata.force really working?
 

In another thread I shared how my system occasionally freezes. I found a solution in which I forced the drive connected to sata port 1 (ata1) to run at 1.5 Gbps and let the second drive connected to sata port 2 run at 3.0 Gbps.

I have multiple systems on this machine. When I boot into Slackware 12.2 with the 2.6.27.58 kernel, I see this in dmesg:

ata1: FORCE: PHY spd limit set to 1.5Gbps
ata1: SATA max UDMA/133 cmd 0x9f0 ctl 0xbf0 bmdma 0xe000 irq 23
ata1: SATA link up 1.5 Gbps (SStatus 123 SControl 300)

Looks okay. When I boot into Slackware 13.1 I see this in dmesg:

ata1: FORCE: PHY spd limit set to 1.5Gbps
ata1: SATA max UDMA/133 cmd 0x9f0 ctl 0xbf0 bmdma 0xe000 irq 23
ata1: SATA link up 3.0 Gbps (SStatus 123 SControl 300)

Further, when I boot into 13.1 the freezing problems return. Therefore I suspect the drive is running at 3.0 Gbps.

1. Why isn't libata.force working?

2. How can I know what speed the drive is running?

Thanks.

the boot option is

libata-force=1.5Gbps

(for all drives)

jumpers will be another way

I haven't seen anything on the web that using the dash version is correct. Regardless, I updated to the 2.6.33.11 kernel and neither the dot nor dash version succeeds.

I'm already using jumpers. :) I want to know why the kernel parameter fails to function with the 2.6.33.x kernel but works as expected with the 2.6.27.58 kernel.

If it is a module, then provide options to it (but this was the situation 2 years ago).