Re: Virtex II multipler performance

"MM" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> "Symon" <[EMAIL PROTECTED]> wrote in message
> news:[EMAIL PROTECTED]
> > Mikhail,
> >     It might sound radical, but if you want it to work at 210MHz, try
> doing
> > the PAR with the constraint to 210MHz! ;-) See what happens and report
> back!
>
> OK, here is my report (use fixed size font to see better):
>
> Requested            Actual
>             -6        -5        -4
> 5            4.986    4.910     5.839
> 4.65         4.561    5.146     5.839
> 4.5          4.328    5.146     5.828
> 4            4.543    5.146     Impossible
> 4.3          4.543    5.146     Impossible
> 4.4          4.328    5.140     Impossible
>
> All of this has been done with default implementation settings.
>
> /Mikhail
>
Hi Mikhail,
    So, looks like you max out at 230MHz with the -6 parts. If you set the
constraint below 5ns the PAR tool gives up on the -5 part, so looks like
4.91 is the best you'll get with -5. Note, if you over constrain, you don't
get the best results! Other options you could consider would be to use the
built in hardware multipliers alternately, i.e. use two multipliers, so that
each one is active every other go. Use the pipelined versions though.
        all the best, Syms.