ISE5.2i strange behavior in PAR (command-line)

Hi all,

I have a 4-FPGA design with nearly identical VHDL source code, so in order to speed development, I started using the command-line tools instead of the Xilinx IDE (which basically also runs the cmd line tools from the shell). I've encountered strange behavior since:

  1. MPPR and PAR with the same cost table generate different results on my PC (w2k, sp3, running 5.2i sp3). This is not such a big issue, as I wrote my own batch to do an MPPR by calling PAR with different cost tables values.

  1. PAR run from the ISE and PAR from the command line generate different results, with identical options and input files (I actually used the .cmd_log file to write my own batch file). More specifically, ISE returns result A, cmd line returns B. Strangely enough, I ran the cmdline tools on another PC, with identical settings, and this returned result A as well.

I browsed through the Xilinx answer database for clues, and I found no.

17134, describing a similar problem. A workaround is presented, but when I implement it (it involves settings the PL_NODIROPT env. variable to 1), I get yet another result, C.

Has anyone encountered this problem before and was able to solve it?

Thanks in advance,

Jo Pletinckx ___________________________________________________________________________

ir. Jo Pletinckx

Ghent University Department of Information technology / INTEC-design

Sint-Pietersnieuwstraat 41 B-9000 GENT Belgium, Europe ___________________________________________________________________________

Reply to
Jo Pletinckx
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I've seen plenty of cases in which different PCs with supposedly identical installations of Xilinx software produce different FPGA images from identical source with identical options.

I've also seen examples of MPPR and SPPR producing different results with the same cost table.

It sounds like you have just one PC, so there must be some difference in the input to PAR (for your point #2), perhaps an environment variable or command line option.

In most cases, the difference doesn't seem to matter. We did find some examples of routes from one PC working while supposedly identical routes from another PC didn't work.

The solution was to test everything in the lab, and avoid reusing the PC configurations that are known to produce bad results.

(IIRC this was all reported to Xilinx some time ago. I think it was happening with 4.x software.)

Regards, Allan.

Reply to
Allan Herriman

I suspect the GUI will pass other unknown settings to the PAR tool, as I use identical options and identical input files for both the GUI based and cmd line based PAR run. I've opened a case with Xilinx to discuss this further.

UPDATE: I set the environment variable PL_NODIROPT=1 on all PCs and now the cmdline PAR on PC_A, PC_B as well as the GUI on PC_A return identical results. Strangely enough, this result is different from the previous ones. (i.e. I now have 3 different end results)

Best regards,

Jo

Reply to
Jo Pletinckx

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