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Subject: Re: Where is now 64 bits Intel's computer?

Author: Jeremiah Penery

Date: 10:47:00 05/12/02

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On May 12, 2002 at 06:42:27, Vincent Diepeveen wrote:

>On May 12, 2002 at 00:31:51, Martin Andersen wrote:
>
>And it is called McKinley and on paper it's impressive
>what it delivers a Mhz.
>
>just a few details i remember:
>  1Ghz , 3MB L2,

The cache number is wrong.  Itanium (and McKinley) have only 32KB of L1 cache
(16KB code/16KB data).  Itanium has 96K of L2 cache, McKinley has only 256K of
L2.  The 3MB is L3 cache, which is on-chip, with 12-cycle access in McKinley (20
cycles in Itanium).

> 6 instructions a clock,

Theoretically it can execute this, but hardly ever in practice (on integer
code).  The reason is that the instructions must be bundled in groups of 6, and
that Itanium is an _in-order_ processor.  If there aren't 6 instructions it can
bundle together, it has to issue a bunch of no-ops in the bundle.  In addition,
the compiler technology for IA-64 is very immature.  I'm sure with better
compilers they will be able to come closer to that theoretical limit.

> not extreme penalty however for misprediction, loads of registers, and a big L1 cache.

There is very little penalty for misprediction, since it has full hardware
predication.  It also has a ton of registers, but it can only access 128(?) at a
time, and the rest it can get through a large rotating register file, which may
have some penalty associated with it, I don't remember specifically.

As I said above, the L1 cache is actually very small.

>What do you need more?
>
>The first cpu was of course not so fast, but making it already was enough
>to impress the world because of the price a cpu intel can make it for.

I'm not sure what you're talking about here.  The Itanium is a very big and very
expensive processor.



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