Answers Database
M1.5iSP2 : XC4000XV net delays changed in the new speed files.
Record #6074
Product Family: Hardware
Product Line: 4000
Product Part: 4000XV
Problem Title:
M1.5iSP2 : XC4000XV net delays changed in the new speed files.
Problem Description:
Urgency: Hot
General Description:
There are several pins delays, net delays, and routing delays that have changed
in the 1.5i Service Pack 2, which is on the web.
Solution 1:
First, Note that this problem concerns a change of speed files - not a change of
speed grade.
The early XV speed files had delays which were both slower and faster than
they should have been. The service pack 2 versions of these files corrected
both classes of errors.
When par runs in timing driven mode it seeks out the fastest way to complete
each net, if a speed file has an excessively fast delay for some feature then
that feature will be perfered by par over other features which would actually
be faster. Now, when trace is rerun with a new corrected speed file, those
routes with a large number of the "prefered" features will slow down greatly.
When you get a new speed file, you must reroute and replace the design
and then compare the timing for the old and new solutions. Just rerunning
the timing analysis with the new file will tell you the true delay for that
routing solution, but it will not reflect the actual performace available
for your design in using that device.
A link to the Software Updates Page:
http://support.xilinx.com/support/techsup/sw_updates/
Or to get the data files for 4000XV, get file 15i_sp2_4kxv_data.exe at
ftp://ftp.xilinx.com/pub/swhelp/M1.5i_updates/15i_sp2_4kxv_data.exe
End of Record #6074 - Last Modified: 04/19/99 16:45 |
