At 10:57 am 2/4/96, J.T. Conklin wrote:
>>> I am now (officially) the proud owner of a Sun3/260 (w/a cgtwo).
>>> Being so inclined, I yanked out the cpu board to have a look.  The
>>> system has a 68020 at 25 Mhz and a 68881 at 20 Mhz.  This seems to
>>> jive with the fact that a 50 Mhz and a 40 Mhz crystal are right
>>> nearby (what the 200Mhz crystal a way over yonder controls, I don't
>>> know).
>>>
>>> Looking at this, I wondered two things:
>>>
>>> 1. Can I put a 68882 in place of the 68881 (and would this be worth it)?
>
>> I don't think so.  They have a different pinout... at least, the
>> ones I have do.
>
>That's odd.
>
>The Sun 3 Archive web pages (http://doener.unix-ag.uni-kl.de/) say
>that the 882 is pin and command compatible with the 881, and is a
>suitable upgrade.  I vaugely remember the 881/882 manual saying the
>same, but I can't check as it's at home right now.
>
>If you replace a 881 with an 882, I wouldn't expect much of a
>performance improvement.  To win you need to unroll loops and
>re-arrange fmove instructions, which gcc doesn't do right now.
>
>        --jtc

*smack*

I just remembered, what I was actually trying to do was to replace a 68020
in a 3/60 with a 68030.  Now those do have different pinouts.  The 881 and
882 are indeed pin-compatible, and do make an upgrade.  The 3/60 at work
has an 882 in it, in fact.

Sorry for the misinformation - blame me for writing emails late at night ;-)

Jules


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