Hi,
Recently we are considering switching from Virtex II to Stratix II. We have evaluated both Synplify 8.1+ISE 7.1i with Virtex 4, and Synplify 8.1+Quartus II 5.0 with Stratix II.
Synplify reports consistent results for several designs. The large one is around 200K gate count (in ASIC), and the smaller ones are CORDIC divider and a SRT R4 divider.
Quartus often gives amazing results. Yes, I mean that. Very amazing. For example, when synplify shows that several muxes and two 26-bit additions in series can only run at 66MHz in Startix II, the post-Quartus results show that this design can run at 160MHz. When synplify shows that a SRT Radix-4 divider can run at 160Mhz, the Quartus results show that it can only run at 87MHz.
I have very few experience of using Quartus. Is it because synplify did a poor job estimating the results for Stratix II device, or Quartus II 5.0 did a very good job on physical synthesis? In the past, we always feel that Synplify's results, though not accurate, are always consistent with ISE's. For the above two cases, SRT and CORDIC, theoretical analysis would favor Synplify's results.
Can someone familiar with Quartus and Stratix II device comment on this? How reliable is the report from Quartus?
Any comment is appreciated!
Thanks!
Regards,
wenchang