Hi, maybe I should give a bit more info. 1. bus mastering helps because it lets the controller do more of the work and offloads effort from the CPU so bus mastering is definitely a good thing in general. 2. DMA can actually harm things if the bursts are log enough because the CPU is halted during the DMA transfer which means it cannot service IRQs nor can it move data itself. The advantage of DMA is that, like bus mastering, a whole bunch of stuff happens wiythout CPU overhead, state saves and restores etc. So Small burst DMA combined with bus mastering can really improve performance. The main issue I was addressing was that of moving data from one spot on a hard to disk to another spot on the same hard disk. This is where the disks on board cache and controller can play an important part in the equation. The normal process is to move the data off the hard disk via the on board cache, then move it back onto the hard disk via the on board cache. Provided the data all fits in the cache there is no problem. Once the data exceeds the cache size then you end up with it going externally, then back onto the drive. This is obviously slower. Because the original destination is in a different spot to the final destination then the heads must also move more. If you have a separate hard disk, you avoid many of these problems. This is also where bus mastering can help more. The data can be run off one hard disk and onto another without much CPU intervention. This is why it is recommended that the hard disk your system runs from is physically different to the one that the audio data is streamed from. Ray -----Original Message----- From: owner-logic-users@m... [mailto:owner-logic-users@m...]On Behalf Of Pipeline@c... Sent: Wednesday, 1 September 1999 10:45 To: logic-users@m... Subject: 2nd hard drive Also Ray suggested that DMA and Bus Mastering do not come into play unless you are transfering audio from one drive to another, so is in fact useless for playing back audio. Is this correct? No, This is not correct I thought that bus mastering was supposed to take the load of the cpu for basic hard disk tasks This is correct Frank W Kooistra .