micky wrote:
One of the watchwords of computers used to be that they only do one
thing at a time, and they just switch from one thing to another very
quickly.

However, now that cpu's have 2 or 4 cores or more, is that still true?

Does my cpu with 4 cores do up to 4 things at the same time?


Then, if it's supposed to make sounds, more than one core can make
sounds at the same time, right?

But if it's supposed to print something or make an image on the screen,
it can only make one at a time!

The cores can do things simultaneously.

You have four computer cores, but only one DRAM bus.

It means the cores have to be served in some sort of
order. If two cores ask for RAM at the same time,
they can't be served at the same time. They take
turns. And the scheme for taking turns has a name,
first come first serve, round robin, strict priority,
and so on.

For printing, printing is serialized by the usage of
a spooler (queues up print jobs) and a print server
(does the printing). No user program is allowed to
drive the printer directly. Some hardware devices
don't have sufficient interlocks to prevent hardware
damage, and only the proprietary driver knows the
correct sequence and timing.

Sound uses the Windows sound mixer, that allows digital
mixing and summation of multiple signals, before they
get to the stereo speakers. Sound is handled in bunches,
rather than single samples. For example, if the sound
driver had to trigger forty four thousand one hundred
times a second, the wheels would fall off. But if
asked to handle forty four buffers of one thousand
samples each, there is less performance loss due to
entering and leaving the mixing routine. And blocks of
sound samples are transported to the buffer on the
sound card, via DMA and ring buffers or the like.

Some things do happen truly simultaneously, but there
are also a lot of choreographed dance routines in
there, where serialization is occurring.

Paul