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Voyager
Voyager
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Registered: ‎10-12-2016

why vivado tool showing intermediate routing summary better than timing after routing ?

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HI Friends, 

I am using vivado 2018.2.   I was supprising that tool showing timing summary before one stage end of routing is better than after routing. Can anyone help on this to uderstand why it is like this ? 

T1Capture.PNG

 

 AFTER ROUTING 

 

T2Capture.PNG

 

 

 

-Sampath
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Teacher
Teacher
358 Views
Registered: ‎07-09-2009

Re: why vivado tool showing intermediate routing summary better than timing after routing ?

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Your results had some numbers better, and others not ,

    so the tools carried on,

Out of interest, have a thought as to what algorithum would you suggest the tools to do in this case,

   

   

<== If this was helpful, please feel free to give Kudos, and close if it answers your question ==>

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Teacher
Teacher
449 Views
Registered: ‎07-09-2009

Re: why vivado tool showing intermediate routing summary better than timing after routing ?

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From what you have posted, it seems that you migh thave over constraind IO pins,

       what was the timming summary ?

have yo uchecked for mutliple clock boundaries ?

 

<== If this was helpful, please feel free to give Kudos, and close if it answers your question ==>
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Voyager
Voyager
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Registered: ‎10-12-2016

Re: why vivado tool showing intermediate routing summary better than timing after routing ?

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HI @drjohnsmith ,

 

I am getting violations on intra paths. 

-Sampath
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Moderator
Moderator
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Registered: ‎05-31-2017

Re: why vivado tool showing intermediate routing summary better than timing after routing ?

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HI @ssampath ,

Can you please check if you have any high-level congestion being reported in your design  while routing?

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Voyager
Voyager
430 Views
Registered: ‎10-12-2016

Re: why vivado tool showing intermediate routing summary better than timing after routing ?

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HI @shameera ,

 

Phase 7 Timing Verification | Checksum: 25d11b3b5

Time (s): cpu = 04:52:24 ; elapsed = 01:21:02 . Memory (MB): peak = 5799.547 ; gain = 1015.875 ; free physical = 114272 ; free virtual = 139188

Phase 8 Route finalize

Router Utilization Summary
Global Vertical Routing Utilization = 15.2249 %
Global Horizontal Routing Utilization = 19.93 %
Routable Net Status*
*Does not include unroutable nets such as driverless and loadless.
Run report_route_status for detailed report.
Number of Failed Nets = 0
Number of Unrouted Nets = 0
Number of Partially Routed Nets = 0
Number of Node Overlaps = 0

Congestion Report
North Dir 1x1 Area, Max Cong = 87.3874%, Congestion bounded by tiles (Lower Left Tile -> Upper Right Tile):
INT_R_X49Y297 -> INT_R_X49Y297
South Dir 1x1 Area, Max Cong = 87.3874%, Congestion bounded by tiles (Lower Left Tile -> Upper Right Tile):
INT_R_X51Y283 -> INT_R_X51Y283
East Dir 1x1 Area, Max Cong = 88.2353%, Congestion bounded by tiles (Lower Left Tile -> Upper Right Tile):
INT_R_X53Y289 -> INT_R_X53Y289
INT_R_X55Y281 -> INT_R_X55Y281
INT_L_X48Y277 -> INT_L_X48Y277
INT_R_X27Y214 -> INT_R_X27Y214
INT_R_X27Y213 -> INT_R_X27Y213
West Dir 1x1 Area, Max Cong = 92.6471%, Congestion bounded by tiles (Lower Left Tile -> Upper Right Tile):
INT_R_X61Y302 -> INT_R_X61Y302
INT_R_X39Y301 -> INT_R_X39Y301
INT_L_X50Y294 -> INT_L_X50Y294
INT_L_X56Y294 -> INT_L_X56Y294
INT_R_X49Y290 -> INT_R_X49Y290

------------------------------
Reporting congestion hotspots
------------------------------
Direction: North
----------------
Congested clusters found at Level 0
Effective congestion level: 0 Aspect Ratio: 1 Sparse Ratio: 1
Direction: South
----------------
Congested clusters found at Level 0
Effective congestion level: 0 Aspect Ratio: 1 Sparse Ratio: 1
Direction: East
----------------
Congested clusters found at Level 0
Effective congestion level: 1 Aspect Ratio: 0.5 Sparse Ratio: 0.5
Direction: West
----------------
Congested clusters found at Level 0
Effective congestion level: 1 Aspect Ratio: 0.5 Sparse Ratio: 0.5

Phase 8 Route finalize | Checksum: 25d11b3b5

Time (s): cpu = 04:52:31 ; elapsed = 01:21:04 . Memory (MB): peak = 5799.547 ; gain = 1015.875 ; free physical = 114270 ; free virtual = 139186

Phase 9 Verifying routed nets

Verification completed successfully
Phase 9 Verifying routed nets | Checksum: 25d11b3b5

-Sampath
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Xilinx Employee
Xilinx Employee
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Registered: ‎05-14-2008

Re: why vivado tool showing intermediate routing summary better than timing after routing ?

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It is reasonable that the post-route timing summary is worse than the interemediate timing.

In your case, in your first screenshot there is a warrning message that is telling you have both setup-critical and hold-critical paths. Router will try to fix the hold violations at the expense of setup slacks. However finally Router failed to improve the hold violations and quit. 

-vivian

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Voyager
Voyager
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Registered: ‎10-12-2016

Re: why vivado tool showing intermediate routing summary better than timing after routing ?

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HI @viviany ,

Thank You. 

You are correct but when intermediate timing is better than final one, then why tool can not point the best one ? Is it tool limitation or something else ? 

 

-sam

-Sampath
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Xilinx Employee
Xilinx Employee
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Registered: ‎05-14-2008

Re: why vivado tool showing intermediate routing summary better than timing after routing ?

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At some point, the router is going to continue optimizing the routing to improve timing. Although the attempts fail to find a good solution finally, it is not necessary to go back to the "better" intermediate result as it was failing timing anyway. At this point, user should report timing and use other various reports to analyze if there is any way that user can do to resolve the both setup- and hold-critical paths. Or start over to try other strategies. Having a better but still failing result does not make things better.

Just my two cents.

-vivian

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Don’t forget to reply, kudo, and accept as solution.
-------------------------------------------------------------------------------------------------
如果提供的信息能解决您的问题,请标记为“接受为解决方案”。
如果您认为帖子有帮助,请点击“奖励”。谢谢!
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Teacher
Teacher
359 Views
Registered: ‎07-09-2009

Re: why vivado tool showing intermediate routing summary better than timing after routing ?

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Your results had some numbers better, and others not ,

    so the tools carried on,

Out of interest, have a thought as to what algorithum would you suggest the tools to do in this case,

   

   

<== If this was helpful, please feel free to give Kudos, and close if it answers your question ==>

View solution in original post