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From: eachus@linus.mitre.org (Robert I. Eachus)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Assembler Programming - Costs versus Benefits
Message-ID: <EACHUS.90Dec5182932@aries.linus.mitre.org>
Date: 5 Dec 90 23:29:32 GMT
References: <1990Nov25.040121.10773@zorch.SF-Bay.ORG>
	<1990Nov30.144853.2562@diku.dk> <7173@sugar.hackercorp.com>
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In-reply-to: peter@sugar.hackercorp.com's message of 1 Dec 90 01:29:45 GMT

In article <7173@sugar.hackercorp.com> peter@sugar.hackercorp.com (Peter da Silva) writes:

   In article <1990Nov30.144853.2562@diku.dk> bombadil@diku.dk(Kristian Nielsen) writes:
  >> It would be interresting (and usefull!) to hear if someone could
  >> comment on the above, add what I have forgotten or don't know,
  >> and correct me where (not if) I'm wrong.

  >I think you've done an admirable job of picking out the problems.
  >About the only one I can think of is that memory above 16M isn't
  >available to Zorro-II DMA, so you better make sure your disk
  >buffers are allocated below that if you do direct disk I/O on a
  >2000 with a 68020 and over 16M RAM.

    And the difference which kills AmigaBASIC:  The 68000 ignores the
upper 8 bits of addresses, but they are valid on the 68020/68030.
Using the upper bits of a pointer as flag bits is a VERY bad thing,
but some people never learn.  It would have been nice if the 68000
checked these bits and trapped, but it doesn't.


--

					Robert I. Eachus

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