Yes, this would be a normal thing. What DMA does is give your HD direct access to the bus as a bus-master device. This means it can talk directly to the memory controller and other bus peripherals without the CPU getting involved. Quite a speed saver.
If you were to leave it at IRQ then that means: (follow me here)
Anytime the HD wants to read or write data, it has to knock on the CPU's door *knock knock* and hope Mr. CPU is home listening, he is home but is out back handling the IRQ that came in from the serial card and you have to wait for him to finish before he comes to the door to even see what the heck you want, let alone do what you need done.
With DMA the HD can just say "Hey, anyone have the bus right now?" and he goes and checks it out himself, if the bus is free he grabs it and get's on with his work. All the while the CPU is still out back goofin off with the serial port...
Just trying to draw a picture here OK. That is kind of a drastic equivelant, but if you think about that as if you were answering your own door if you were busy, it should make sense.
Hope this helps.
DS Sultan
[url=www.artistcollaboration.com]Collaboration Central[/url]
Bookmarks