Quartus II Fitter advice

Hi again,

Many thanks for all the responses. I have been studying the Design Space Explorer for the last few hours and it seems quite useful. I had read about it before but I don´t know why I hadn´t experimented with it before now.

I have read a little about the Timing Optimisation Advisor also but I haven´t quite gotten around to doing much with it yet.

Anyway, my plan is to specify a range of seeds and let the DSE run overnight. I ran it for two seeds this morning and it took 40 mins, so i am thinking of specifying the seeds as 1 - 25 or so. It should take about 7 or 8 hours I think. I´m not sure if this is even reasonable. From what I understand, the effect that a specified seed has is completely random, so specifying more seeds should give me a better chance of getting a better result? Should I specify as many seeds as possible for the time I have, or once a certain number of seeds is used, does the result not improve significantly?

Also another question I have reagrding the fitter. I noticed that when compiling my design, sometimes the fitter may take ~5 mins while after a very minor change it can take almost 7 mins. When it takes 5 mins the results are always worse (i.e. more timing warnings), while when it takes 7 mins the results are always much better. Does anybody know what the fitter is actually doing in the 2 extra minutes that it sometimes takes?

I presumed that if it didn´t meet it certain requirments that it would try some extra effort or something to that effect. But why does it not always do this if it is consistently not meeting the requirments?

I also see it prints to the screen the following:

"Info: Started fitting attempt 1 on Mon Nov 10 2008 at 15:49:57"

for 3 different attempts. Why does it do the 3 different attempts. Judging by the times specified, it does the first 2 in a matter of seconds and the the 3rd takes much longer.

Thanks for your help.