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Happy New Year to all Commodore 64 enthusiasts as we step into 2023. C64 OS continues to enjoy strong sales, much to my satisfaction. Currently, I am preparing for the fourth stock run and expect to resume accepting orders by the end of January. Meanwhile, beta testing is underway for updates v1.02 and v1.03 to ensure smooth functionality before their release on the Software Updates page. The v1.02 update is minor but important, addressing a bug in the Installer Utility that affects subsequent update installations. The v1.03 update includes multiple new features, which I will detail in a future weblog post.
I’d like to share a glimpse into the assembly process at OpCoders Inc., where C64 OS bundles are prepared for shipment. Many users have inquired about the compatibility of C64 OS with devices like the 1541 Ultimate II+ and Ultimate64. These devices are complex and multifunctional. The Ultimate64 serves as a full modern C64 replacement, and I have successfully demonstrated C64 OS on it at recent Commodore events. The 1541 Ultimate II+ offers numerous features, acting as a REU, GEORAM, multi-SID emulator, KERNAL ROM replacement, speed loader cartridge, real-time clock source, and digital audio module, among others.
While C64 OS works well with these devices when connected to a C64, the question often arises whether C64 OS can be installed on and boot directly from the 1541 Ultimate II+ or Ultimate64. The simple answer is no. This limitation stems from the fact that these devices emulate 1541, 1571, or 1581 disk drives using disk image files rather than physical floppy media. Traditional disks have insufficient capacity and lack support for subdirectories, both essential for C64 OS installation. This explanation, detailed in the User's Guide, clarifies why installation on these drives isn’t feasible.
Users also ask about Software IEC compatibility. Software IEC supports subdirectories and native USB file system access, theoretically making it suitable. However, it currently lacks sufficient compatibility with other supported device families such as CMD HD, RamLink, IDE64, and SD2IEC, all of which maintain high DOS compatibility with one another. Through detailed correspondence with a C64 OS user and potential software developer, I outlined the compatibility gaps between Software IEC and these devices. While developers of 1541 Ultimate II+ and Ultimate64 firmware have shown interest in improving Software IEC compatibility, progress and timelines remain uncertain.
Using an Ultimate64 running version 1.41 - 3.10a for testing, I attempted to catalog the incompatibilities. The differences are extensive, so a top-down explanation of expected behaviors is more effective. Developers must decide whether to maintain their own unique implementations or seek high compatibility with established mass-storage devices. Given that C64 OS version 1.0 supports DOS commands and path structures common to multiple devices, I advocate for the latter approach.
Historically, Creative Micro Designs (CMD) enhanced the CBM DOS to support multiple partitions, subdirectories, and advanced file operations including date/time stamps and RTC commands. This extended DOS was introduced with the CMD HD in 1990 and later adapted for CMD FD-2000 and RamLink, all sharing near-identical DOS functionality despite hardware differences. The IDE64 followed in the late 90s and 2000s, copying CMD’s DOS commands and syntax to preserve compatibility, adding some unique commands. The SD2IEC arrived in the mid to late 2000s, continuing this tradition, though my knowledge on its early history is limited due to a hiatus from the Commodore scene during that time.
