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From: dave@hp-lsd.COS.HP.COM (David C. Mueller)
Newsgroups: comp.realtime
Subject: Re: Predicting Execution Times for Processors with caches
Message-ID: <15630005@hp-lsd.COS.HP.COM>
Date: 12 Apr 90 15:54:17 GMT
References: <765@telesoft.com>
Organization: HP Logic Systems Division - ColoSpgs, CO
Lines: 15

>
>Even if you disable the 68020's caches, you still must worry that your
>runtime data may be misaligned in memory.  The 68020 will happily
>compensate for this, slowing down your program considerably.  In my
>opinion, you should stop thinking about the 68020 for real-time
>systems, and start thinking about highly deterministic RISC processors
>such as the R2000, or perhaps the MC88000.

	This problem can be resolved by assembler/linker tools.  The
assmelber I'm familiar with has an option whereby any symbol can be
forced to a 32-bit boundary.

	I like to think of the 68020 as providing me with the option of
code space optimization and memory size independence by aligning 16
and 8 bit values on byte boundaries.