Compatibility issues due to the 0.25% system slowdown

[sy2002]

When running in HDMI flicker-fix mode, we are slowing the whole system (not only the CPU, but everything including the whole C64 system (CIA, SID, VIC, ...) and the C1541) down by 0.25%, so we are only running at 99.75% of the official speed. This leads to a great silky smooth scrolling experience on HDMI, but also leads to some software not working.

The tapemag / diskmap Input 64 Issue 1/1985 is known to have this problem: It works fine without the HDMI flicker-fix but it does not work with the HDMI flicker-fix: iput0185.d64.zip

[sy2002]

Current status: There is a menu item called "HDMI: Flicker-free". If you switch it off, then the system runs at 100% and for example above-mentioned Input 64 Issue 1/1985 works like a charm.

We leave this issue open, because the root-cause of this behavior is completely in the dark. "Theoretically" no software should ever notice, that it runs on a slightly slower machine...

[sy2002]

Commit 313c468 fixes this issue. We decided it is too "dangerous" to go into Release 4 at this time, since we would need to do a lot of regression testing, including all the demos. If you need this fix before Release 5, here is an experimental, unreleased core that fixes the issue. It is based on "Release Candidate 2 for Release 4":
C64MEGA65-313c468.zip

[sy2002]

As described above: We consider this issue as fixed. But the fix will not be released before Version 5 of the core. So we leave the issue open so that people who run into the issue can download this Alpha version of Version 5 that fixes the issue.