I am reasonably new to digital PC editing but I am finding my feet pretty fast. One item I keep coming across is to make sure that DMA is enabled. This means absolutely nothing to me and I would appreciate any answers to the following:
1. What is DMA
2. Why does it matter
3. How do I make sure it is functional
Any reasonably simple answers to this will be greatly appreciated.
Thanks
SIFI.
DMA means Direct Memory Access.
My understanding is that it is a way of getting work done in a way that largely bypasses the computer's CPU.
This avoids putting the CPU under unnecessary strain that could impact on the performance of that particular task and also other tasks that may be going on at the same time.
We have a definition of DMA in the back of the magazine (Computer Video, that is), but it's a lot shorter than that one.
If you'd like to find out more, you can do what I do when I need this sort of info - use the amazing search engine at www.google.com.
Searching for DMA didn't do the trick, so I searched using the expression,
Direct Memory Access - what is it?
This came up with a bunch of explanations, including the one at:
http://www.oreilly.com/reference/dictionary/terms/D/Direct_Memory_Access.htm
Bob C (who still gets no fees from google, sadly, but still remains hugely impressed with its search capabilities)
DMA = National Association of Dyslexics?
Dave
Dyslexia lures - KO!
Basically DMA means that your add-in cards (or, in this case, the hard disk controller) can read from and write to the system memory directly behind the CPU's back, so the CPU only has to set up the DMA transfer and can then go on to other things while the hardware does its job independently. So, for example, when one program wants to read a data file the CPU can tell the disk controller to read in a megabyte of data from the drive and write it to a particular area of memory, then go off and run another program while it waits for the disk controller to tell it that the data has arrived. Without DMA the CPU would have to read the data from the disk controller and write it to RAM itself, which would be slower and prevent it from doing anything else at the same time.
In the old days this was handled by a DMA controller on the motherboard (hence the DMA channel setting you'll see on a lot of old ISA cards), but today it's normally performed by the add-in board itself because the motherboard DMA controller is an antique that's really only there for backward compatibility.