DMA questoins

[chrisojeda]

Okay....I am still learning so be nice

What is DMA?

What is UltraDMA?

By using the Device manager to bring up the Properties Dialogue Box for either a Hard Drive or CD-ROM there is a check box for "DMA". When should I check this for CD-ROMs or Hard Drives?

Thanks...

It worked yesterday! :lol:

 

[machow]

DMA stands for Direct Memory Access, which means that all data that use DMA will flow to the memory bypassing the need for the processor to crunch more numbers. UDMA is just an extension. DMA could be good for performance, but the price would be data cleanliness. Though most device can use DMA without problems at all.

------------------
This site is cool.

 

[ejsmith2]

What the last guy said.
+
Turn on DMA for everything you have, but if you have REALLY (>4yrs) old hardware, it may lock up the system. UDMA is just DMA with an extra letter. There's about 5 different 'modes' of DMA, starting with 2 they call it UDMA.

 

[r2k]

Enable DMA checkbox and you'll get a great performance increase over heavy data read/write on every device.
These are the different modes of UDMA:

UDMA Mode 2 or UltraATA/33 : Transfer rate of 33.3 MB/second
UDMA Mode 3 : Transfer rate of 45 MB/second
UDMA Mode 4 or UltraATA/66 : Transfer rate of 66.6 MB/s
UDMA Mode 5 or UltraATA/100: Transfer rate of 100 MB/s

Remember that these numbers are theoritical maximum rates possible and that between the controller and the chipset (not what the drive is actually capable of).Also UDMA Mode 3 was never used because UDMA Mode 4 technology became easily available and there are no devices for that.Check this site for better explanations and comparisons:
www.storagereview.com