07-16-07 06:20 PM
On Jul 13, 7:40 am, "Fred Kleinschmidt"
<fred.l.kleinmschm...@boeing.com> wrote:
> The above doesn't really do the two simultaneously. The two processes
> may appear to be working at the same time, but in reality one process
> gets some time, then it is rolled out and the other process gets some time
,
> then that one rolls out and the first task resumes, etc.
That's a misleading statement for a variety of reasons. The primary
one is to assume that a process is only accomplishing useful work when
that process is running. For example, when a process goes to write
some bytes to a file, they are likely only copied into memory. The
system continues to do useful work on behalf of that process even
while another process has been switched to.
> The only way to do it truly simultaneously is if you have two separate
> processors.
Untrue. A modern computer system contains numerous agents that are in
fact capable of operating concurrently. For example, disk can read
data into its local cache while the CPU is doing something else. In
may cases, the disk can even transfer data out of main memory using
DMA while the CPU is doing something completely different.
DS
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