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From: Lawrence D'Oliveiro <ldo@nz.invalid>
Newsgroups: comp.arch
Subject: Re: Is Intel exceptionally unsuccessful as an architecture designer?
Date: Tue, 24 Sep 2024 23:46:35 -0000 (UTC)
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On Tue, 24 Sep 2024 13:19:32 -0500, BGB wrote:

> On 9/20/2024 4:33 PM, Lawrence D'Oliveiro wrote:
>>
>> On Fri, 20 Sep 2024 09:55:53 +0200, Terje Mathisen wrote:
>> 
>>> Lawrence D'Oliveiro wrote:
>>>>
>>>> The way I understood to do flicker-free drawing was with just two
>>>> buffers -- “double buffering”. And rather than swap the buffer
>>>> contents, you just swapped the pointers to them.
>>>>
>>> If you cannot swap the buffers with pointer updates ...
>> 
>> Surely all the good hardware is/was designed that way, with special
>> registers pointing to “current buffer” and “back buffer”, with the
>> display coming from “current buffer” while writes typically go to “back
>> buffer”. Why would you do it otherwise?
> 
> VRAM isn't free, and the older graphics hardware (before the era of 3D
> acceleration and the like) tended to only have a single framebuffer
> (except, ironically, for text modes).

But flicker-free updating requires at least two. And even the original 
1984/1985 Macintosh could manage two, and the Amiga had its clever 
“copper” which split those buffers down to individual scan lines. With the 
base-register scheme, you don’t need more than two buffers. Yet I 
frequently hear of “triple-buffering” going on, which seems unnecessary to 
me.