MDEC and FPGA utilization (Patreon)

Hi everyone,

most of you probably have already seen my recent twitter post with the MDEC video some days ago. If you haven't seen it yet, you can find  here: https://twitter.com/AzumFpg/status/1454377353174454280

I want to wrap it up here in short: the MDEC, which is used for movies and compressed images, is feature complete. All color modes are implemented and the handling with both CPU and DMA works. 

The speed is slightly(~10%) too fast, so it may need to be slowed down a bit, but I will wait for the games to really measure it.

I also want to use the chance and present the overall review of the FPGA utilization this time.

57% of the FPGA logic is filled now. It seperates into 40% for the PSX core and 17% for the MiSTer Framework.

For the largest single components, the GPU is filling 12% of the FPGA, GTE about 8%, CPU about 7% and MDEC about 5%.

The DSP(Multiplier) usage is quiet high already with 88% used, but all modules that need large amounts are done and in worst case the GPU can be optimized further to use less.

Internal Memory is nearly unused. I have no plans yet for it, but CD and SPU might take a slice of it. Overall it should be no issue.

I also added the timing result to show that there is currently no timing pressure.  The CPU could run at about 43Mhz, but only needs ~33Mhz and the GPU, GTE, and MDEC could do 78Mhz but only need ~66Mhz.

This leaves us with a very important conclusion:

There is currently nothing from FPGA side preventing any further progress. There is plenty of room left and the timing allows for additional logic(new features or bugfixes) in the already designed parts.

Next on the list is the CD handling and this will be a huge task. Not only is it complex in itself, but also requires communication with the framework for getting data just-in-time, e.g. from SDCard.

This will easily take the rest of the year, but i still hope to have at least 1 game running without sound on MiSTer by the end of this year. 

First intermediate step is to boot one of the working demos from CD instead of the .exe interface that is used currently. Hopefully I have this running end of November.

Have fun!