Re: your mail

Ed Casas (edc@ece.ubc.ca) Thu, 14 Sep 2000 22:41:02 -0700 

Date: Thu, 14 Sep 2000 22:41:02 -0700
From: Ed Casas <edc@ece.ubc.ca>
Subject: Re: your mail



> In today class, Dr. Casas said that we have to avoid using
> different clock signals whenever possible.  I just wonder why
> computers nowadays use 3 different clock speeds: one for CPU,
> one for system bus, one for SDRAM.  Will it better to use just
> one clock speed??

Different clocks are unavoidable in large systems (otherwise the
whole word would have to be hooked up to one master clock!).

However, interfaces between different clock domains have to be
designed with care to make sure they'll operate reliably.  We'll
learn about some of these issues (e.g. metastability) later in
the course.

I believe the three clocks you mention in your example are
actually synchronous since they are generated by dividing or
multiplying one master clock.

PS: Please make sure your e-mail has a meaningful `Subject:' line
and wrap your text so there are less than 80 characters per line.

Thanks,

-- 
Ed Casas   edc@ece.ubc.ca   http://casas.ece.ubc.ca   +1 604 822-2592