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Seattle, WA, USA

Posted Thu Feb 29, 2024 9:57 am

Sharing this fun news via my friend Kentsu in regards of a recent update for Ozmoo, a Z-machine interpreter for the Commodore 64 and similar computers.

Reposted from Commodore 128 Enthusiasts group on Facebook (post by Fredrik Ramsberg):
We just updated Z-code interpreter Ozmoo, adding support for building games for computers with dual 1571 drives. This means you can play games up to 512 KB in size on a C128. Have you played Infocom's biggest game, Trinity? Trinity weighs in at 256 KB, and that's a large game. But there are larger games out there, released after Infocom closed up shop. To play a game built for dual 1571 drives, you need either:
  • Two 1571 drives
  • *or*
  • One 1571 drive + an REU (512 KB or bigger).

For the most convenient gameplay, you want an extra drive (1541, 1571 or 1581) for game saves. If you ever thought you'd never have any real use for three drives, you were wrong! ;)
If you have an REU, Ozmoo can also use it for Undo, as well as for a scrollback buffer.
You can upload Z-code files and build disk images at
Just to demonstrate this new feature, I built three awesome, large Inform 6 games, which should play pretty well on a C128, espescially on the 80 column screen, as this means the CPU can run faster. These games are between 490 and 512 KB in size. You can download this little collection at ...

It was asked if there was device number and/or CMD partition support possible.

Fredrik Ramsberg:
As for device number, you can insert the boot disk/story disk 1 in drive 8,9,10 or 11. The game will then tell you to insert the second disk in the lowest device (8 or 9) which isn't occupied by the boot disk/story disk 1. As for a save drive, the game lets you pick a device number 8-11. If there's a game disk in that drive, you will be instructed to change it when saving.
The low-level format of the save disk isn't important, so long as it's possible to save and load files, and read a directory from the drive.

The story disks must be on drives which have the low-level format Ozmoo expects, as story data is not stored in files, but in raw sectors. I don't know how CMD partitions work. If they support virtual 1571 disk images, where sector read-commands are supported, Ozmoo can probably use them.

I look forward to trying this out soon with both dual drives and REU to compare experiences. The problem I've always run into, however, is trying to write D71 images to real disks. So maybe I start with a (sigh) Ultimate1541+ and an REU...?

Update: Any REU should work that has sufficient space, including 3rd-party options (e.g. CMD 1750XL).

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