I think I’ve identified a reproducible behavior difference between the internal drive of the C64 Ultimate (I have a Starlight) with latest factory firmware version 3.14, and an external 1541 Ultimate II+L.
Using the same C64 Ultimate system, same DOS ROM, same disk images, and same titles, the software loads correctly with the 1541 Ultimate II+L but fails with the internal drive.
This suggests a timing or IEC behavior discrepancy in the internal drive emulation, independent of the DOS implementation used.
Titles affected include, for example, Steel Ranger.
This is not a request for third-party software support, but a technical observation that may be relevant for firmware accuracy.
C64 Ultimate internal drive vs 1541 Ultimate II+L – reproducible behavior difference (also compared to real C64 hardware)
I would like to report a reproducible behavior difference involving the internal drive of the C64 Ultimate, confirmed through multiple comparison setups.
Test configurations used:
- C64 Ultimate
Internal drive enabled
JiffyDOS KERNAL enabled
JiffyDOS drive ROM enabled
- C64 Ultimate + external 1541 Ultimate II+L
Same C64 Ultimate system
Same JiffyDOS configuration
Same disk images
- Real C64 hardware
Original C64
Internal JiffyDOS KERNAL installed via EEPROM
External 1541 Ultimate II+L
Same disk images
Software tested:
Steel Ranger
Ghosts’n Goblins Arcade was only used to test if JiffyDOS was detected. This game also loads on a C64U with JiffyDOS enabled.
Observed results:
C64 Ultimate – internal drive
Titles fail to load
C64 Ultimate + 1541 Ultimate II+L
Titles load correctly
Ghosts’n Goblins Arcade explicitly reports “JiffyDOS 5.0” during loading
Real C64 + 1541 Ultimate II+L
Titles load correctly
Behavior matches the external-drive configuration on C64 Ultimate
This indicates that:
JiffyDOS itself is functioning correctly
The same drive emulation works as expected on:
real hardware
external 1541 Ultimate II+L
The failure appears specific to the internal drive emulation of the C64 Ultimate
This strongly suggests a timing or IEC behavior discrepancy in the C64 Ultimate’s internal drive, rather than a third-party software issue.
This is not a request for third-party support, but a technical observation intended to help identify a possible firmware-level inconsistency.
I would be interested to know if other users can reproduce this behavior.
I continued to do some testing and discovered something incredible but true! With an IEC cable connected to the C64U's serial port with nothing plugged into the other end, and JiffyDOS running on both the kernel and the emulated 1541 drive A, the Steelranger game loads correctly. Without the IEC cable connected, it doesn't load.
I think I’ve identified a reproducible behavior difference between the internal drive of the C64 Ultimate (I have a Starlight) with latest factory firmware version 3.14, and an external 1541 Ultimate II+L.
Using the same C64 Ultimate system, same DOS ROM, same disk images, and same titles, the software loads correctly with the 1541 Ultimate II+L but fails with the internal drive.
This suggests a timing or IEC behavior discrepancy in the internal drive emulation, independent of the DOS implementation used.
Titles affected include, for example, Steel Ranger.
This is not a request for third-party software support, but a technical observation that may be relevant for firmware accuracy.
C64 Ultimate internal drive vs 1541 Ultimate II+L – reproducible behavior difference (also compared to real C64 hardware)
I would like to report a reproducible behavior difference involving the internal drive of the C64 Ultimate, confirmed through multiple comparison setups.
Test configurations used:
Internal drive enabled
JiffyDOS KERNAL enabled
JiffyDOS drive ROM enabled
Same C64 Ultimate system
Same JiffyDOS configuration
Same disk images
Original C64
Internal JiffyDOS KERNAL installed via EEPROM
External 1541 Ultimate II+L
Same disk images
Software tested:
Steel Ranger
Ghosts’n Goblins Arcade was only used to test if JiffyDOS was detected. This game also loads on a C64U with JiffyDOS enabled.
Observed results:
C64 Ultimate – internal drive
Titles fail to load
C64 Ultimate + 1541 Ultimate II+L
Titles load correctly
Ghosts’n Goblins Arcade explicitly reports “JiffyDOS 5.0” during loading
Real C64 + 1541 Ultimate II+L
Titles load correctly
Behavior matches the external-drive configuration on C64 Ultimate
This indicates that:
JiffyDOS itself is functioning correctly
The same drive emulation works as expected on:
real hardware
external 1541 Ultimate II+L
The failure appears specific to the internal drive emulation of the C64 Ultimate
This strongly suggests a timing or IEC behavior discrepancy in the C64 Ultimate’s internal drive, rather than a third-party software issue.
This is not a request for third-party support, but a technical observation intended to help identify a possible firmware-level inconsistency.
I would be interested to know if other users can reproduce this behavior.
I continued to do some testing and discovered something incredible but true! With an IEC cable connected to the C64U's serial port with nothing plugged into the other end, and JiffyDOS running on both the kernel and the emulated 1541 drive A, the Steelranger game loads correctly. Without the IEC cable connected, it doesn't load.