| 1 |
On Mon, Oct 24 2011, Michael Mol wrote: |
| 2 |
|
| 3 |
> On Oct 24, 2011 7:21 PM, "walt" <w41ter@×××××.com> wrote: |
| 4 |
>> |
| 5 |
>> Now, lack of DMA is another story for hard disks, certainly. Here's |
| 6 |
>> where my ignorance of hardware limits my thinking: |
| 7 |
>> |
| 8 |
>> AFAIK the device driver *always* sits between the disk drive and the |
| 9 |
>> DMA hardware, doesn't it? |
| 10 |
> |
| 11 |
> DMA means a device is told where in the system's address space it may write |
| 12 |
> to, and it writes directly to that place without further CPU involvement. |
| 13 |
> Since drivers run on the CPU, the drivr isn't a go-between. |
| 14 |
> |
| 15 |
> When the CPU *is* involved in the passing of bits around, things slow down. |
| 16 |
> IIRC, that's called PIO--programmed IO. |
| 17 |
|
| 18 |
Correct. DMA stands for direct memory access; the device has direct |
| 19 |
access to the memory. PIO is indeed the name when the CPU acts as a go |
| 20 |
between. |
| 21 |
|
| 22 |
allan |
Archives