On Thu, 29 Aug 2002, Andy R wrote:

> Isn't the dreamcast a 200mhz sh3 chip? I know
> megahertz aren't everything, but it's fun to know.
> 
> Does anyone know how it compares to a i386 or sparc or
> something?


  200 MHz SH-4 chip. A friend introduced me to the architecture a couple
of years ago; it's neat.


  It's a RISC-style chip with 16 or 32 registers. Pretty normal in most
respects, but has support for a 4-element dot product 
(single-precision). My tentative understanding is that it can crank out
one of these per cycle (pipelined), but it's been over a year since I read
the spec sheets.

  There's also some support for using this feature to do vector/4x4 matrix
multiplication, which is why the chip works so well in consoles (very good
at geometry transformation).

  Double-precision math must be emulated, if I understand correctly.


  The SH-4, like its predecessors, is designed for embedded
applications. It consumes very little power, and has integrated memory and
peripheral controllers out the wazoo.


  The SH-_5_ has been mentioned in press releases now and then, but I
haven't been able to find concrete information on it (last check was
several months ago). I have no idea whether this has been released, or
canned, or is still in progress.

Ttyl,
				-Christopher Thomas