TeensyROM cart won't boot to menu when delaying boot through core select menu

[dansanderson]

The TeensyROM utility cartridge can load its menu in GO64 mode with MEGA65 core v0.95, but is not detected with core v0.96.

I confirmed this on an R3 mainboard. v0.95 is not available for the R6 mainboard, and I don't need it to be. I'm noting the difference between the two cores in case it helps identify a reason why TeensyROM is not currently working with the MEGA65 core.

Repro:

1. Power off the MEGA65.
2. Connect TeensyROM to the expansion port.
3. Hold No Scroll, power on. In core menu, select MEGA65 core v0.96.

Expected: Boots to GO64 mode, opens TeensyROM menu.
Actual: Boots to MEGA65 mode.

Repeat with MEGA65 core v0.95. It performs the expected behavior.

Both the working case with core v0.95 and the non-working case with core v0.96 were using ROM 920408, so it's not expected to be a difference in the ROM startup procedure.

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We're interested in TeensyROM working with the MEGA65 core because 1) it's neat that some features already work with GO64 mode, and 2) we'd like to someday have a MEGA65 branch of the menu software, USB MIDI features, etc. Getting this working with the latest core on an R6 board will help us test features that may rely on R6-exclusive bidi I/O.

We're also interested in TeensyROM working with the C64 core. As of C64 core v5.1, TeensyROM is not detected as a cartridge and does not boot to the menu. This is a separate issue and not expected to be related to this one. MJoergen/C64MEGA65#143

[dansanderson]

Thanks to Amok I already have an update, related to a comment on the other C64MEAG65 thread:

If I disable the C64 core auto-boot by updating its properties in the core selection menu, such that no core is the target of C64 cart auto-boot, powering on with TeensyROM connected will boot the MEGA65 core and it correctly detects it, boots to GO64 mode, and runs the menu successfully.

So this is not necessarily a MEGA65 core regression, just an oddity of the boot sequence when booting the MEGA65 core manually from the core selection menu. As per the C64MEGA65 thread, this may be related to reset timing: the core select menu causes too much time to pass for the TeensyROM to boot properly. Maybe the fixes discussed on the other issue are sufficient for this.

[dansanderson]

Actually I'm just going to close this. If we think of a behavior that the MEGA65 core should have to better accommodate TeensyROM I'll file a new issue.