Sprite talk…

I did some more tests. Made a test rom even for the real system (as no emulator handles this yet). I got full sprite bandwidth, but it required clipping the display on the right 3 cell (24 pixels). Not bad. Not baaaadd at all. For those unfamiliar with what I’m talking about, on the PCE if you set the display too wide – there’s not enough time during ‘hblank’ (hblank on the system side, not just the actual signal) to process and fetch all the sprite pixels for the scanline. So the VDC starts to drop two sprites at a time. I was a little worried that too much clipping would be required for all sprites to be processed on a scanline. But this wasn’t the case, thankfully.

Right now, I have HSW=2, HDS=1, HDE=4, HDW=$1C, VDW=$1E1, VDS= $1f. I still have to setup an RCR routine to see if there’s double h-sync INT calls. But if so, not a problem as you just use even numbers (zero out the last bit of the scanline number). This is pretty exciting. I need to sharpen up the demo with some fresh graphics and release it to the pce community for people to test out different systems. This should be the same on all systems since there are no ‘A’ revisions to any 6270’s that are known (only 6260’s and 6280’s). But better to be safe. For all my tests currently, have been on the original white PCE. I’ll test out on a US Duo and SGX tomorrow (well later today, but I need to sleep still).

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