FreeBSD 5.3b7and poor ata performance

Søren Schmidt sos at
Mon Oct 25 11:00:32 PDT 2004

Thomas Sparrevohn wrote:
> On Monday 25 October 2004 18:28, Victor Balada Diaz wrote:
>>On Monday 25 October 2004 18:12, fandino wrote:
>>>Thanks to the excelent job of Thomas Sparrevohn I get 52MB/s, this is
>>>an excerpt of their comments:
>>>"Changes the DMA speed to 66 - The Controller is a 100 controller and the
>>>disks are 100 Disks but I think the default for the controller is 66 and
>>>hence there are most likely a small initialisation difference between
>>>Linux, NetBSD and FreeBSD"
>>please can you post how do you solved the problem?
> atacontrol mode <channel> DMA4 DMA4
> atacontrol mode <channel2> DMA4 DMA4
> The reason is that the motherboard only supports ATA100 on two out of four IDE 
> channels and hence you need to force the two other channels to run at DMA66 

How do you come to that conclusion ? There is no such limitation AFAIK.

However you can only get a total sum of 133MB/s divided by number of 
disks (and minus some overhead on older system there is typically 
110MB/s effective bandwidth)..

The real explanation is much more likely that the timing specs are 
marginal (overclocked ?) for the disks, which causes problems..



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