Re: New Math Coprocessor - who has a need for it???

[blasjw@ntmtv.com (Joseph Blas)]

In article <3PIFBR8V@minnie.zdv.uni-mainz.de> kapffer@Informatik.Mathematik.Uni-Mainz.DE (Matthias Kapffer) writes:
>In article <1993Jul13.110208.8271@ifi.unizh.ch>, gudat@avalon.physik.unizh.ch (gudat henrik) writes:
>[...]
>|> Furthermore, the NC consists of the finest parts only (sockets, ceramic
>|> carriers etc.). This also means that the card is rather expensive (ca.
>|> $200 without the 68882).
>                    ^^^^^
>                    |||||
>
>I believe to remember that this card (as well as the FPE) has been announced with
>the 68881. From the descriptions I have read, the difference between the 68881
>and the 68882 (besides the 1) is *not* the time needed for the operations itself
>(calculating sin(), etc.), but enhanced parallelism with the 680[23]0 CPU
>resulting in a speedup of about 20%.
>
>Does anybody *know* if a 882 would bring any advantage in an Apple II ? The NC
>was designed for clock rates up to 25 MHz (according to my memory ...); do 882
>FPUs with a higher rating have a better availability/price ?
>
>
>				- Matthias Kapffer

 I compared the technical summaries of the two chips and it sounds
like what you said may be true.  Here are the 3 features listed for the
68882 that were not listed for the 68881:

  1 Special purpose hardware for high-speed conversion of binary real
    memory operands to and from the internal extended format.

  2 Reduced coprocessor interface overhead to increase throughtput.
  
  3 Concurrent instruction exection of multiple floating-point.

 I don't really understand 1, but 2 sounds like the enhanced
parallelism with the 680[23]0 that you described.  Maybe 3 means that
too, I don't know.  Given this info., maybe somone can answer your
quesiton about whether the 882 would be any better than the 881       
for the Apple II.

 As far as availability, I haven't seen the 68882 listed in any of my
catalogs.  I did see the 68881 listed though.  In one case it was a 20
MHz model selling for I believe $65.  Anyway, it looks as though
availability of the 68881 is better.  I would imagine that the price
for the 68882 is a bit more than the 68881.


                   Regards,

                    Joe

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