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From: mitchalsup@aol.com (MitchAlsup1)
Newsgroups: comp.arch
Subject: Re: except what, is Vax addressing sane today
Date: Sun, 22 Sep 2024 18:40:31 +0000
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On Sun, 22 Sep 2024 11:30:00 +0000, John Dallman wrote:

> In article <fcc1d80b06e991bf9a27b64ff973b720@www.novabbs.org>,
> mitchalsup@aol.com (MitchAlsup1) wrote:
>> On Sun, 22 Sep 2024 0:14:49 +0000, Chris M. Thomasson wrote:
>>> On 9/21/2024 4:29 PM, Lawrence D'Oliveiro wrote:
>>>> Aren't branches that are not taken supposed to be fast?
>>> Well, they are not taken, so they should be faster... ;^)
>> It is NOT the speed, it is the code bloat.
>
> Yup. Bigger code is always a potential problem, not so much because it
> takes up RAM nowadays, but because it takes up memory bandwidth and
> cache
> space. Using up cache space is always bad, because bigger caches are
> slower, and instructions seem naturally smaller than cache blocks.
>
> Wanting smaller code isn't an argument against RISC, but an argument
> against poorly optimised ISA design. Variable-length CISC makes it
> easier to get smaller average instruction sizes but has other drawbacks.

Variable length RISC makes it easier, too.

> For the stuff I work, on ARM64 code is consistently smaller than x86-64,
> although the factor varies by platform.
>
> John