From: Toby Thain <toby@telegraphics.com.au>
To: tuhs@minnie.tuhs.org
Subject: Re: [TUHS] 68k prototypes & microcode
Date: Thu, 4 Feb 2021 06:28:49 -0500 [thread overview]
Message-ID: <c9996136-fe05-226f-a2f8-b87d717e773f@telegraphics.com.au> (raw)
In-Reply-To: <20210204072326.GZ4829@ancienthardware.org>
On 2021-02-04 2:23 a.m., Arno Griffioen wrote:
> On Wed, Feb 03, 2021 at 05:33:56PM -0800, Larry McVoy wrote:
>> I have to admit that I haven't looked at ARM assembler, the M1 is making
>> me rethink that. Anyone have an opinion on where ARM lies in the pleasant
>> to unpleasant scale?
>
> 'Different' is what I would call it..
>
> Years ago I did a bunch of assembly hacking on the original ARM2 used in the
> Archimedes A3000, which was an amazingly fast CPU for the time.
>
> The thing that stood out on these CPU's to me, which was wildly different
> to what I was used to (M68K, 6502, Z80/8080, VAX), was the fact that
> many instructions were (somewhat) composeable.
>
> Aka. you can/could add varuous logical operations like AND, OR, etc. 'into' an
> instruction like a load or store and it would take the same number of clock
> cycles to execute it all in 1 go.
That is immediately reminiscent of DG Nova, PDP-8 (and to a tiny extent,
PowerPC).
>
> That was great for doing data manipulation at very high rates for the time
> compared to the common CISC CPU's as you did not need to go through multiple
> fetch and modify cycles.
>
> Reminiscent of some VLIW setups, but still more 'human readable' :)
>
> The original ARM1/2/3 design did have some oddities like status bits being
> encoded in the top of the (23) address bits, which meant that later versions of
> the original design had to do some memory tricks to use a bigger address
> space and keep compatilibity to the original code.
>
> I suspect the current common ARM revisions since the move to the StrongARM
> (ARM4) architecture, when DEC got involved and ARM became a standalone chip
> design firm, have long fixed those oddities.
>
> Probably still retains the way in which it encodes it's instructions to make
> a lot of common logic operations while shuffling data more efficient though..
ARM MCUs also have the "bit manipulation engine" for a similar goal, I
think.
--Toby
>
> Having said that.. (and bringing it more back to TUHS instead of COFF ;) )
>
> The ARM2 and ARM3 based machines could already run UNIX with Acorn selling
> RISC iX for a short time, which was a 4.3BSD port done in the late 80's
> and early 90's.
>
> Very few of those were ever used/sold though as the Acorn Archimedes series
> of machines were quite a bit more expensive than more widespread CISC machines.
> Most were found in the UK and often in universities and the like.
>
> Bye, Arno.
>
next prev parent reply other threads:[~2021-02-04 11:29 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-29 10:49 [TUHS] AT&T 3B1 - Emulation available Arnold Robbins
2021-01-29 13:49 ` Ronald Natalie
2021-01-29 14:37 ` Clem Cole
2021-01-31 7:57 ` arnold
2021-01-31 8:41 ` Rich Morin
2021-02-03 7:53 ` emanuel stiebler
2021-02-03 7:59 ` arnold
2021-02-03 8:53 ` Ed Bradford
2021-02-03 8:58 ` arnold
2021-02-03 10:13 ` Ed Bradford
2021-02-03 14:58 ` Clem Cole
2021-02-03 15:33 ` Henry Bent
2021-02-03 16:53 ` Clem Cole
2021-02-04 0:41 ` [TUHS] 68k prototypes & microcode John Gilmore
2021-02-04 0:52 ` Al Kossow
2021-02-04 1:10 ` Arthur Krewat
2021-02-04 1:33 ` Larry McVoy
2021-02-04 1:47 ` Al Kossow
2021-02-04 1:57 ` Al Kossow
2021-02-04 7:23 ` Arno Griffioen
2021-02-04 11:28 ` Toby Thain [this message]
2021-02-04 15:47 ` Arthur Krewat
2021-02-04 16:03 ` emanuel stiebler
2021-02-04 21:55 ` Dave Horsfall
2021-02-04 22:11 ` Steve Nickolas
2021-02-04 22:39 ` Adam Thornton
2021-02-04 22:47 ` Henry Bent
2021-02-05 14:42 ` Michael Parson
2021-02-04 22:56 ` Richard Salz
2021-02-04 23:14 ` Steve Nickolas
2021-02-04 1:35 ` Clem Cole
2021-02-04 2:18 ` Dave Horsfall
2021-02-04 15:53 ` Arthur Krewat
2021-02-05 2:16 ` Dave Horsfall
2021-02-05 2:53 ` Larry McVoy
2021-02-04 1:14 ` Clem Cole
2021-02-04 1:20 ` Clem Cole
2021-02-04 14:56 ` John Cowan
2021-02-03 15:20 ` [TUHS] AT&T 3B1 - Emulation available emanuel stiebler
2021-02-03 16:48 ` Doug McIntyre
2021-02-03 10:46 ` emanuel stiebler
2021-02-03 11:13 ` arnold
2021-02-05 12:44 ` Sergio Pedraja
2021-02-07 7:32 ` arnold
2021-02-17 16:07 ` emanuel stiebler
2021-02-17 22:00 ` Ed Carp
2021-02-17 22:14 ` Larry McVoy
2021-02-18 1:30 ` Ed Carp
2021-02-18 7:59 ` arnold
2021-02-18 18:07 ` Brad Spencer
2021-02-13 1:06 [TUHS] 68k prototypes & microcode Jason Stevens
2021-02-13 2:30 ` Gregg Levine
2021-02-13 4:34 Jason Stevens
2021-02-13 6:05 ` Toby Thain
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