1541 Ultimate

I came across this interesting C64 hardware add-on project some time ago and I was so impressed over it that I ordered one for myself right away. I have had it for some time already, so maybe I could write some thoughts about it.


1541 Ultimate with travel speakers

In short, 1541 Ultimate is a floppy drive replacement for Commodore 64, hence the name. It’s a SD card based solution which allows you to store and use disk images on the SD card as if they were floppy disks on a real drive. But it doesn’t end there. 1541 Ultimate offers an impressive list of great features that makes it perhaps the single best peripheral ever made for C64  to date. I’m not going to copy-paste the specifications and feature list here, those can be found from the project site.

When I got my unit, I honestly had an empty feeling for a while. I realized that 1541 Ultimate made just about every C64 peripheral I had obsolete and even offered more. Now that I have grown out of that empty feeling, here’s a little sum-up of my thoughts on the device.

Ultimate floppy drive replacement?

First, 1541U is not the only memory card based solution to replace a real floppy drive. There are other projects such as 1541-III, SD2IEC and the likes that allows the IEC bus of Commodore 8-bit computers to interface with a memory card or some other mass media. Unlike the previously mentioned devices, 1541U emulates the complete 1541 floppy drive which makes it nearly 100% compatible. It even emulates the lovely sound that the floppy drive makes when operating! So if you connect speakers to 1541U you can actually hear what the virtual floppy drive is doing. That’s quite something.

Another interesting and unique approach is that 1541U works like a freezer cartridge, which makes it possible to have an on-screen UI for the device. Press a button and the C64 halts what ever it is doing and the 1541U user interface will pop up on C64’s display. From there you are able to browse the SD card contents, choose disk image to be mounted in the virtual drive, run programs directly (practically without loading times) and configure the settings. Running programs is pretty much like using a C64 emulator. It’s that simple and straight-forward, really.

1541U can also be used in ‘stand-alone mode’ when it is connected only with the ‘floppy cable’ but not into expansion port. When used like this, it needs to be externally powered via mini-USB and you lose the on-screen UI and the rest of the features.

And talking about the rest of the features…

Since 1541U is plugged into the expansion port in the normal operation mode, it makes it up by featuring cartridge and REU emulation. It means that you can simply select between The Final Cartridge III, two versions of Action Replay, Retro Replay, Super Snapshot v5 and Turbo Assembler with Codenet or ‘no cartridge’ from the configuration menu. Wicked.

The same goes with REU. It can be either disabled or enabled and configured to be in a range of 128k to 16M. Now if I just had the slightest idea what to do with 16 megabytes of memory on my 64. The REU and compatible cartridges can be used simultaneously.

And to top it all, the 1541U can be ordered with RR-net compatible Ethernet option.

Use experiences

My 1541U is the Ethernet version from production batch four and came with 1.6+ firmware. My experiences with the device have been very good. The only compatibility issues that I have faced have been with demos that automatically detect disk change. In some cases the disk change is not detected at all or some demos may crash. In some rare cases even the device itself hangs. I’m hoping firmware updates will improve the compatibility to disk change detection. Otherwise the drive emulation works perfect.

The cartridge and REU emulation work just as fine as the drive emulation. It’s worth noting though that for example some demos don’t like cartridges, memory expansions or multiple devices on the IEC bus – were they real or emulated by 1541U. So some stuff will not work if those have not disabled.

The network functionality I haven’t yet tested.

One thing to note is that the size of 1541U board is too big to fit into a standard cartridge case. So if you don’t want the 1541U sit “naked” in the back of your Commodore, you need to consider some sort of DIY case. There are at least two different DIY cases being sold, too.


All in all, the 1541 Ultimate is a wonderful device for C64 hobbyist. Tip: If you’d like to have one, act fast! Probably the last manufacturing patch is about to be made this fall. 1541U’s are sold directly by the manufacturer and are made according to pre-orders. It’s very unlikely that these devices will appear to second-hand market much. Details about the project at the 1541 Ultimate site.


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