Screen (playfield) shaking with certain DPC+ ARM driver

[sa666666]

It seems we may have another ARM driver that should use the 'old' behaviour (as defined in CartDPCPlus c'tor). Relevant link is https://atariage.com/forums/topic/302951-text-adventure.

text_adventure.bas.zip

I can confirm that using the old myFractionalLowMask in CartDPCPlus fixes this issue, but I want to be sure that is actually the issue, and not a bug in the code. The same ARM driver works on Harmony, so I'm thinking it's not a bug in the ROM, but that we need to handle another ARM version in the c'tor.

[thrust26]

The ROM seems to work without problems on my hardware too.

[SpiceWare]

I did a preliminary investigation in this blog post:

https://atariage.com/forums/blogs/entry/16565-dpc-jitter

I plan to look into it some more to see if I can figure out which driver versions should exhibit the DPC+ jitter issue with the Fractional Data Fetchers.

[SpiceWare]

I've written a script to automate the discovery of DPC+ versions and creation of the test ROMs with each driver version. I posted it in the comments of the above blog post.

To help find other driver versions I've put out a request on AtariAge for DPC+ game ROMs.
https://atariage.com/forums/topic/303575-need-help-with-stella-and-the-dpc-jitter-issue/

[sa666666]

Some fixes are already in, thanks to SpiceWare: 9ff00c3.

I'll leave this issue open until we take care of this for good. I think we're pretty close now.

[sa666666]

I haven't heard anything else from @SpiceWare, so I guess we can close this one.