How to Force UDMA100 Mode on Boot?

Mark Kane mark at
Tue Aug 16 00:39:29 GMT 2005

Hi, thanks for the response. The thread somehow got broken up due to 
some subject formatting (there was a space inserted somehow). Here are 
the threads:

I have 5 hard drives, and when copying data between them in certain 
configurations (such as drive placement) I get READ and WRITE wouldn 
errors. All the cables are brand new, as are two of the hard drives.

Similar errors happened on the last board I had. I had the same model 
(Giga-Byte K8NS Pro) a couple months ago that had other issues in 
addition to this. I sent it to the factory for a RMA, and a brand new 
one came back. Before I sent it in, I was using Windows XP and it would 
automatically downgrade it to 100 so I wouldn't see any errors. When I 
switched over to FreeBSD and it tried to operate in 133 mode, I got 
errors instead of the OS trying to hide it.

Note that throughout this whole problem I never got a "FAILURE" message 
until today, except that is only on one drive, and one that I think is 
in fact going bad.

It's gotta be something with the controller.

I can't get you the dmesg info right now since I'm doing a scan on that 
one hard drive that I think is failing. But it is an nForce 3 chipset on 
a Giga-Byte K8NS Pro motherboard.

I would really like to solve the DMA problems, but if not I think the 
easiest is trying to downgrade it to UDMA100 on boot, which is what this 
post is about.



jason wrote:
> Mark Kane wrote:
>> Hi everyone. I've had a thread going here on the lists about DMA 
>> problems in 133 mode. In a nutshell, some drives give DMA_WRITE and 
>> DMA_READ errors when in 133 mode with certain configurations, however 
>> don't have any problems in 100 or 66 mode. After looking in to many 
>> solutions I think I'm just going to run it at 100, since from my 
>> research the benefit isn't that noticeable.
>> I know about atacontrol to set it manually, but I'd like to set 
>> UDMA100 mode automatically on boot since I have 5 hard drives. I also 
>> know the sysctl hw.ata.ata_dma, but that doesn't say anything about 
>> using 100 vs 133.
>> Thanks in advance.
>> -Mark
> Sounds like a cable issue, but could it be a buggy bios?  How about some 
> information since I did not see your previous postings.
>  > dmesg|grep DMA
> atapci1: <nVidia nForce2 UDMA133 controller> port 
> 0xf000-0xf00f,0x376,0x170-0x177,0x3f6,0x1f0-0x1f7 at device 9.0 on pci0
> ad0: 38172MB <MAXTOR 6L040J2/A93.0500> [77557/16/63] at ata0-master UDMA133
> Also if I don't have a cd in the drive I get "acd0: CDRW <LITE-ON 
> LTR-40125S/ZS0K> at ata1-master PIO4" for acd0.  If there is a disc in 
> the drive it is set to UDMA66 at boot up.   Or first use  if it was not 
> in at boot.

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