Then, as the old adage says, … “don’t do that.” Periodically, we get a complaint from someone who is becoming concerned about the time it takes to stream out GDSII from their P&R tool in order to run Calibre. We keep making Calibre faster and faster, so eventually the stream-out time starts to look big and hairy. In the typical final verification loop, you may have to do this whole stream, verify, fix, stream, verify, fix, a few times. If the verification time is 2 hrs and it takes more than 20 minutes to stream out, you start to get concerned about the stream time.
The root of the problem is that, if you are doing final verification, you need to merge the top-level from the P&R tool with the cells that contain the base layers. In some modern design flows, this can mean merging literally 100’s of files with the top level and streaming it out. P&R tools are famous for being slow at doing just this.
Luckily, there are several cures for this ill. First, instead of doing the merging in the P&R tool, you can stream out only the top level from the P&R tool and use Calibre to merge the libraries on input. This is very easy and can be implemented very quickly. If you want to got even further, you can introduce another step in the middle where you use Calibre DRV’s filemerge utility to merge the 100’s of input files and then push it into Calibre DRC.
The table below shows the results from just such an example with a real customer test case.
- merge in P&R and stream out : 120 min
- merge on input to Calibre : 60min
- merge with calibredrv filemerge : 8min
So, just using the right tool for the job gives a 15x improvement in the time to do the merging that you have to do before you even get to running verification.