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theblotted
Dec 24, 2006, 01:50 AM
sorry i'm not quite sure where this thread belongs, so please move this if necessary.

i've been reading about problems in Mac Pro and past BootCamp versions, esp regarding SATA performance issues. my understanding is that there's 2 modes: PIO and DMA; and DMA has better performance (esp under Ultra DMA).

i know that this affects Windows, but is it the same for Mac's? how does one go about finding out if my SATA is PIO or DMA in OSX? is it benefitial to change to DMA (if it's possible)?



Anonymous Freak
Dec 24, 2006, 02:25 AM
sorry i'm not quite sure where this thread belongs, so please move this if necessary.

i've been reading about problems in Mac Pro and past BootCamp versions, esp regarding SATA performance issues. my understanding is that there's 2 modes: PIO and DMA; and DMA has better performance (esp under Ultra DMA).

i know that this affects Windows, but is it the same for Mac's? how does one go about finding out if my SATA is PIO or DMA in OSX? is it benefitial to change to DMA (if it's possible)?

It's DMA by default. Pretty much any reasonably modern OS on modern hardware will be using DMA, no settings needed. PIO mode is positively ancient, being already obsolete in 1998. (If your disk was operating in PIO mode, you would get a maximum of 16.7 MB/s data transfer rate, and you'd be using up massive processor time, just for that.)

I'm not even certain Serial ATA supports PIO mode. It probably does, simply because 'backward compatibility above all' is the rule in PC hardware, but it really shouldn't support it. (Even 'just plain' DMA is obsolete, only the 'Ultra DMA' transfer modes are current. The fastest available over Parallel ATA was 133 MB/s, and Serial ATA is now up to 300 MB/s.)

theblotted
Dec 24, 2006, 03:12 PM
It's DMA by default. Pretty much any reasonably modern OS on modern hardware will be using DMA, no settings needed. PIO mode is positively ancient, being already obsolete in 1998. (If your disk was operating in PIO mode, you would get a maximum of 16.7 MB/s data transfer rate, and you'd be using up massive processor time, just for that.)

I'm not even certain Serial ATA supports PIO mode. It probably does, simply because 'backward compatibility above all' is the rule in PC hardware, but it really shouldn't support it. (Even 'just plain' DMA is obsolete, only the 'Ultra DMA' transfer modes are current. The fastest available over Parallel ATA was 133 MB/s, and Serial ATA is now up to 300 MB/s.)

thanks for the reply.

is there a way to find out max data transfer rate of the drives in my MP thru software? or do i have to manufacturer's website?

electronbee
Dec 24, 2006, 07:06 PM
A lot of sites, Tomeshardware (http://www.tomshardware.com) have interactive charts that are updated at least every quarter with drives that they test.

They also list the software that they use so you can download it and see what yours test at.