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Re: [OFF-TOPIC] Cobalt 64-bit, what for? (was: 64-bit fix)

To: Dominic Sweetman <>
Subject: Re: [OFF-TOPIC] Cobalt 64-bit, what for? (was: 64-bit fix)
From: Ralf Baechle <>
Date: Fri, 15 Apr 2005 11:25:48 +0100
Cc: Dominique Quatravaux <>, Peter Horton <>,
In-reply-to: <>
Original-recipient: rfc822;
References: <20050414185949.GA5578@skeleton-jack> <> <> <>
User-agent: Mutt/1.4.1i
On Fri, Apr 15, 2005 at 11:18:08AM +0100, Dominic Sweetman wrote:

> > > And doesn't 64 bit mode have costs of its own (doubled i-fetch bandwidth
> > > for starters)?
> 64-bit MIPS CPUs still have 32-bit instructions... it's the registers
> and addressing range which grow, not the instructions.

True - but number of instructions will grow, thus the bandwidth needed to
fetch them.

> Program data segments tend to grow when you use 64-bit pointers (N64
> does, but N32 - paradoxically still a 64-bit ABI - doesn't)

N32 is an ILP32 ABI so I'd count it as 32-bit.


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