Why does DMA make things worse?

Hak Foo · 25-February-08, 01:44 AM

So I hooked up my LS-120 (I liked it so much I bought four spares!) to an IDE-SATA convertor (it's the only thing it DOES work with

) and let it sit.

Tonight, I went through my old floppies, and had APPALING performance. It kept seeking and re-seeking, and averaged less than 1KB per second on copies.

The weird thing: It seemed that the speed of copy was primarily related to the number of files, not their size.

The drive was set to 'Multi-Word DMA mode'. I turned off DMA, and bang wow, my copies were 100KB per second, probably approaching the promised "LS-120 reads regular discs faster" line. The drive now runs in PIO mode 3.

Why would it be so? DMA is usually good.

capt_cope · 25-February-08, 06:18 AM

Drivers? I know in linux DMA was baaaaaaaaaad for me and my dvd drive.

25-February-08, 01:44 AM		#1 (permalink)
Hak Foo Apex Elite Tech	Why does DMA make things worse? So I hooked up my LS-120 (I liked it so much I bought four spares!) to an IDE-SATA convertor (it's the only thing it DOES work with ) and let it sit. Tonight, I went through my old floppies, and had APPALING performance. It kept seeking and re-seeking, and averaged less than 1KB per second on copies. The weird thing: It seemed that the speed of copy was primarily related to the number of files, not their size. The drive was set to 'Multi-Word DMA mode'. I turned off DMA, and bang wow, my copies were 100KB per second, probably approaching the promised "LS-120 reads regular discs faster" line. The drive now runs in PIO mode 3. Why would it be so? DMA is usually good.

25-February-08, 06:18 AM		#2 (permalink)
capt_cope Apex Master Tech Apprentice	Re: Why does DMA make things worse? Drivers? I know in linux DMA was baaaaaaaaaad for me and my dvd drive.

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