Re: Multi-core processors

[Erik Wikström <erik-wikstrom@xxxxxxxxx>]

Danial Thom wrote:
> I find it rather interesting that all of the
> intel-bashing "testers" are now reporting that
> there is "no performance gain" from dual-core
> processors which has always pretty much been the
> case with DP systems. It seems that its going to
> take quad-core processors to see real gains over
> "designed for UP" operating systems, how long do
> you think its going to be before such animals are
> available?

The gains of dual-code is very dependent on the type
of applications being run and how many of those. But
generally speaking most applications today are single-
threaded and thus does not gain anything from dual-core

However if you run two or more applications at the same
time they can both execute at the same time which gives
a performance gain. However it will not be as big as
when using two processors if they are memory-intensive
since both cores share the same bus.

The difference can easily be noticed if you are heavily
multitasking, the GUIs of applications will become more
responsive and the computer will feel snappier over all.

You might want to take a look at AnandTech for a
comparison of single- and dual-core:
http://www.anandtech.com/cpuchipsets/showdoc.aspx?i=2388

> Also, does anyone know if dual-core processors
> share a cache, which I suppose would provide for
> more efficient cache use, or are they just 2
> separate entities wired together?

A shared cache would probably not be such a great idea if
the size is not doubled or more since there are now two
cores competing to use the cache. If I remember correctly
the L1 cache on Pentium D is separate and the L2 (or maybe
L3?) is shared.

--
Erik Wikström