Re: Number Cruncher FPUs

[dirk@gaga.maschinenbau.uni-dortmund.de (Dirk Froehling)]

In article <4ounvh$h6e@disunms.epfl.ch>, dinarich@di.epfl.ch wrote:

>Well, it depends because this kind of fpu takes a great number of cpu cycles
>in order to achieve most floating instructions .
>Here is some instruction's execution time in clock cycles (taken from
MC68881 Floating-Point Coprocessor User's Manual):
>
>FABS  650    (PS: these # are without effective address calculation time and
>FASIN 606         are suitable for double calculation)
>FCOS  416    
>FDIV  130
>FLOGN 550
>FMUL   98
>
>Even the fastest 68881/2 will not finish most instructions within 1 Mhz master
>clock cycle. 

I think the difference between the 881 and 882 is that the 882 has more
instructions hard-wired and uses less clock cycles. There is a big performance
difference between the two when used on a Mac.
So with a 881 your point is valid, but I don't know about the 882...

-- 
| Dirk Froehling - Germany, Uni Dortmund, FB Maschinenbau, LS Mechanik |
| dirk@gaga.maschinenbau.uni-dortmund.de            GEnie: D.FROEHLING |