Thursday, 25 May 2017

1541 Ultimate II Guide 6 : D71 and D81 images

When you want to use your 1571 or 1581 drive with your C64 or C128 it's nice to be able to use the hardware to the fullest. That means using double sided floppies and enormous 800k disk images!

Later 1541 Ultimate 2 (1541U2) firmware levels support reading D71 and D81 images in the cartridge interface, but it cannot mount the images as it emulates a 1541. Duh!

It would be neat though if you could use the 1541U2 cartridge to write the D71 and D81 images to physical floppies.

I've written a program to do just that:

D71 and D81 images can be written using this C64 program, which is available on CSDB:

You can find the source here:

The latest version is 1.1. This program works with 1541U2 firmware 2.6 and up.

You need to prepare some things on the 1541U2 before you can use it though:

1) Enable the REU in the 1541U2 cartridge, with at least a size of 1MB.
2) Enable the command interface in the 1541U2
3) Disable any cartridge in the 1541U2 as it can interfere with the REU functionality and the command interface
4) Format the floppy before using this program
Optional) When running the program on a C128 (in C64 mode) you need to modify the 1541U2 option CPU addr valid after PHI2 to 100ns

Place your D71 or D81 file somewhere on the USB or SD card and run the program. Follow the instructions, it is self explanatory. Writing a disk takes quite some time (11 to 20 minutes) so make sure you have a cup of coffee nearby.

Now this version is released, I am concentrating on creating a C128 native version which will use the burst commands for faster writing.

Until then, have fun!

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