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Apr 05

Of Simulation and Synthesis

I’ve made significant progress on my 6502 FPGA Emulation, and even have a mostly complete layout of the NES Picture Processing Unit.  I set up a test-bench that included RAM and cartridge simulation and logged the processor output to a text file that could be compared to the “golden” nestest log.  I was able to debug all of the documented instructions and had begun to implement some of the undocumented instructions when I decided to try and load the processor into my FPGA. Unfortunately, this is where I learned that just because something can be simulated doesn’t mean it can be synthesized.

Log Comparison

The synthesizer choked on my design, and it may have given me some feedback if a let it churn for a while I decided to cut my losses and redesign my core.  My original code was admittedly inefficient, and generally terrible, so I was expecting to make a second version anyway.  I was able to perform numerous simulations and learned a lot along the way, so I’m satisfied with what was accomplished.  I’d say I’m about 50% complete on my second attempt and should have much more success in the synthesis department.

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