DMA?

[mfb tampa]

What is it?
How can I tell if my machine has it?
If so, how do I turn it off?
Augh! Why is this PTF program freezing and locking up my AMD K62 486, 128 RAM Soundblaster live machine?

[Morningstar]

PTF is, I believe, incompatible with K6's. Go to the search page and look for other posts about K6 problems...

[choctop]

Warning, Long post.

Ok, can of worms here, but I'll do my best...

DMA (direct memory access) is a fairly recent spec improvement to MB's, hard drives and CD Roms that improves disk access times by reducing the load on the CPU by bypassing it for some disk functions. For us, that means better audio performance.

You can enable DMA by going to Control Panel>System>Device Manager>Disk Drives>Generic Disk Drive (or whatever is listed as your hard disk controller)>Properties>Settings and check the box DMA. You'll be prompted for a re-start. After you re-boot, go back to the same place and look at the DMA box.IF it's still checked, congrats, your MB and drive supports DMA. What speed you're getting depends on your MB/drive combination, but it might be 33, 66 or 100 mBits per sec. If it has become un-checked, sorry.... DMA not supported by something in your chain.

Here comes the tricky part... the DMA setting affects BOTH devices on that particular bus, so if I have my hard drive and CDRom Drive on my Primary bus (Disk as master, CD as slave) and I enable DMA for my hard drive, that setting ALSO inflicts DMA on my CDRom drive. This may or may not be a good thing!! Some CD Burners in particular insist on having DMA turned off.

What you need here is screwdriver, a lot of patience and some benchmarking software (I use SiSoft's Sandra 2000). Run the Disk benchmark on your current machine. Then, if you feel confident, pop the hood and check your disk/config. For instance, if you ONLY have a hard drive and a CDRom in your machine, and they are BOTH on the primary bus, you can shift your CD to the secondary Bus (don't forget to change the jumpers on the CD Drive to master...) and that way you can set DMA for each device seperately.

If you have more than two devices, things get a bit sticky, but I'm sure you get the idea...

Hope this helps.

Matthew