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Seattle, WA, USA

Posted Tue Jun 29, 2021 8:43 am

What an amazing time to be a part of the Amiga scene.

Thirty-five years after the release of the Amiga and over 27 years since Commodore went bankrupt and ceased operations, its devoted fanbase continues to support and innovate for the classic hardware.

The last version of AmigaOS shipped by Commodore was version 3.1, which was delivered across various machines between 1992 and 1994. Since that time several Amiga Oses, either inspired by or built directly off of 3.1, have been created - the most recent being OS 3.2 in May of 2021!

Ever since 1990 with the release of the Amiga 3000 and AmigaOS 2.0, the Amiga’s original OS was often forgotten by many developers, and understandably so for the times.

AmigaOS 2.0 was created to be both more widely accepted by the mainstream public and easier to develop on for programmers. As such “Old Blue” was mainly left behind with one key exception: games. If a Game Dev wanted to hit the largest possible market, they’d want to include the millions of people around the world rocking A1000s, 2000s and in particular the most popular Amiga of all time - the A500. All of these machines shipped with 1.3 at some stage. In fact, even some early A3000’s shipped with it as well. So most Devs made sure their games were backwards compatible to 1.3 up until the day Commodore died. It just made financial sense.

It’s not that AmigaOS 1.3 couldn’t have provided everything the later versions did via Public Domain software enhancements, it was often more a matter of Commodore keeping up with design trends while trying to push AmigaOS as far into the future as possible to stay relevant and fresh when the company was still alive and trying to scratch out any marketshare they could.

Well, we know how that wound up.

It doesn’t mean the core 1.3 experience wasn’t absolutely brilliant. (Note: you can make the 1.3 User Interface totally gray if that makes you feel better.) And to that end, some folks are keen to still making 1.3 a dynamic and evolving user experience even today in 2021.

Chris Brenner, the Californian who reverse engineered the Microbotics StarDrive for the Amiga 1000 earlier this year, has been busy creating software to make his life easier when using his original Amiga. He likes to use the machine the way it was in the era in which he bought it. And being a talented engineer, he’s decided to design and develop some very cool software specifically for OS 1.3.


One of the key ways people have shared Amiga software over the years is through the use of ADF files.

The ADF file format is an image of an original floppy disk; it is a track-by-track dump of a disk’s data as read by the Amiga operating system. If one wants to “share” a disk with a friend, all he needs to do is create an ADF version of that disk and send his buddy the digital file.

That file can then be written to a fresh floppy or read by an emulator as if it were a physical floppy disk. It could also be read via emulation either on a modern PC or even a floppy drive emulator like the GoTek. They’ll see the ADF as a floppy disk and mount it as if it were loaded on classic hardware.

For many years this type of solution has been possible on Amigas running 2.0+. With the right hardware, Amigans could copy large batches of ADF files of their favorite games and software over to their classic hardware to mount and run them from their desktop.

OS 1.3 users, however, didn’t have quite the same flexibility because the software simply wasn’t there. It wasn’t an OS deficiency, it was a lack of software support.

Brenner decided to fix that problem.

Introducing diskmimic.device and Disk Mimic.

The diskmimic.device allows you to mount disk image files that are stored on your hard drive. This software was written primarily for use with ADF images, but there's really no reason that it can't work with other types of disk images as long as you have a suitable file system, and in the case of ISO images, enough space on your hard drive.

The diskmimic.device is based on Matt Dillon's fmsdisk.device, and is very lightweight; it accesses the disk image file directly from the hard drive instead of loading it into memory. Mounting a diskmimic.device drive uses only 192 bytes, and after inserting a disk image it uses about 15 KB.

- An Amiga running OS 1.3
- ReqTools 1.0d or later
- den.font 6 point font
- A hard drive or other form of mass storage

All of the necessary software and tools are in the package provided by Brenner. You can install it manually or use his custom installer program.

Using this software requires updating one’s mountlist file to add however many drives you want your machine to support. You also need to update your Startup Sequence if you want those drives to mount automatically on bootup. Finally, depending on your setup choices the program’s icon Tool Types might need some very minor adjustments. But the installer script handles all of that for you if you don’t want to do it yourself.

Most people will probably want to customize their setup, so the installer script sets up two drives as a starting point.

The diskmimic.device supports up to wacky 32 drives, while the Disk Mimic GUI can “only” handle 8.

Following Brenner’s concise and easy to understand instructions, I manually added four drives: 3 “normal” floppy drives and one FFS drive for the rare occasion I might need one.

To use the software using the GUI, simply click the floppy icon next to the drive you want to “insert” an ADF file.
Click the disk icon to "insert" an ADF. Click the little eject icon on the right side of the GUI to eject it. Or, insert another ADF into the same drive and it will automatically eject what is in there already.

Browse to an ADF on your machine and it will instantly load it onto the desktop. It will even tell you how much space is being used on that “disk”.

If you have a game or program that uses more than one disk, feel free to load up as many ADFs as you want assuming you updated your mountlist to support it.

If you need to swap a disk, Disk Mimic will automatically eject the disk in the drive before inserting the new one. You can also manually eject any disk.

Since DiskMimic drives behave just like real drives, you can use Diskcopy to write and read ADFs to and from floppy disks!

You can even create a blank ADF by making a copy of an ADF image,  inserting that image into a DiskMimic drive, and then formatting it.

The program window can me resized as needed, and you can modify the ToolTypes to open the program at whatever size and location you prefer on launch.

At the end of the day it all seems so simple. And yet it took us all these years to get here. All I can say is: hats off to Chris Brenner for giving us OS 1.3 folks something the other guy’s might finally want, too. Besides early classic games, that is.

Download Disk Mimic here.

It has also been submitted to Aminet. UPDATE: it is on Aminet.

I know for a fact that Disk Mimic will become a part of my core software titles that get installed to all of my machines. It's that helpful and that well-made. Enjoy! And let Chris know what you think.

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Posted Tue Jun 29, 2021 11:55 am


I love software for 1.3.

That was the OS that made Amiga so special for me. Including the color choice.

Once/when (if?) I get my physical Amiga up and running again, tinkering with OS 1.3 is definitely on my list.

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Dallas, TX

Posted Tue Jun 29, 2021 2:37 pm

Very, very cool! Can't wait to try this out, and many thanks to Chris for the dedication and hard work!

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Posted Wed Jun 30, 2021 2:52 am

Awesome video and article! Your videos are always filled with such love, care and devotion for old blue, it really comes through. Feels so wholesome to watch!

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Posted Wed Jun 30, 2021 3:41 am

Nice! Small footprint and well styled too with the smaller font.

Where do we find Chris on the interwebs? I googled but couldn't find anything. I'm curious what else he has done!

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Seattle, WA, USA

Posted Wed Jun 30, 2021 9:00 am


Crispy also invented the incredible MMDC Retro Player in 2016.

He's not a social media guy, however, if that's what you're looking for.

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Posted Wed Jul 07, 2021 2:28 pm

Finally tested it tonight and it's awesome ! Thx Mr Brenner ! You're a boss <3

And the installer is also unbelievable ! I've got AmigaBootSelector installed, so the installer couldn't find the startup-sequence but I've not got an error... 'cause it added lines in my custom "user-startup" ! Amazing !

I added 2 more units in my "Disk Mimic". It's a very useful application for 1.3 ! I already made an icon for AmiDock an putted Disk Mimic in it <3

Just the perfect app ! Thx !

The only thing which could improve it : put the name of the disk near DI0: in the UI.

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Seattle, WA, USA

Posted Wed Jul 07, 2021 4:12 pm

The only thing which could improve it : put the name of the disk near DI0: in the UI.
I like that idea, Batteman. Did you know if you hold the ALT key it will show the disk name? Regardless, having it appear next to the DIX: would be pretty cool.

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Posted Wed Jul 07, 2021 4:24 pm

During development, I tried a build with the disk volume name next to the DIx: device name, and I didn't like it. I felt that it made the interface too busy and cluttered. I opted instead to put in a hotkey (LEFT-ALT) that could be used to display the volume name where the disk stats normally are.

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Posted Wed Jul 07, 2021 9:45 pm

Alt key!
I knew I saw it somewhere! I should have read the manual one more time...

So, I must say it, Disk Mimic is perfect! <3

Thx for this wonderful piece of work!

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