Amiga Emulation 101

Hey everyone! I mentioned I've been working on an Amiga article. Sadly I got sidetracked: I had to upgrade to Windows 10, and found myself thwarted when moving my existing Amiga setup from the Linux laptop. I could have worked out the culprit (smart money's on memory corruption on the USB stick) but troubleshooting bores me to tears. I decided to make a new installation instead, with all the usual programs necessary for coding on the Amiga. At which point I realized, hey, someone other than me might find this useful.

So, in short, here's how to set up an easy-to-use Amiga 1200 desktop environment on either Linux or Windows.

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Setting up the A1200

Ah, the trusty Amiga 1200. In my opinion, the 1200 sits closest to the sweet spot of the Amiga experience: faster than the 500, reasonably inexpensive to purchase, with four times the chip memory, gobs of expansion options and of course the AGA graphics. Back then, it was as if someone had taken the 500 and improved it across the board.

Of course, in hindsight, it wasn't a perfect machine. Blitter fill rates, sound quality, number of hardware sprites and floppy drive capacity hadn't kept pace with the other improvements. The AGA architecture, while more capable in certain areas, lacked the elegant, Swiss-watch interconnectedness of the OCS and ECS machines. Mostly, the 1200 was too little and too late, debuting half a decade after the point of being able to replicate the revolution that the original Amiga 1000 had been.

Nevertheless, the 1200 remains the easiest way to achieve a reasonable desktop experience on a low-end Amiga. Therefore, while the A500 or A2000 may be a "purer" way of experiencing the Amiga, this is not what we'll do in this instance. Instead, we'll emulate an Amiga 1200.

This tutorial has the following prerequisites:

• a modern desktop, preferably running Windows 7/8/10 or Linux,
• an internet connection, and
• a ROM file of the A1200's kickstart chip (see below),
• a full set of Workbench 3.1 floppy disks (or images thereof), and
• snacks (optional).

The kick-rom (that is the kickstart file) is an image of the physical ROM chip that sits on the Amiga 1200 motherboard. The 1200 was originally released with version 3.0 of kickstart; the difference to 3.1 is fairly marginal and should not matter much for this tutorial. What does matter is that the emulation software we're going to use requires the kick-rom file to operate. Without that ROM file, the emulator will not run, and the ROM file is not free to distribute.

How to get a kick-rom file? Well, if you own a physical Amiga 1200 with access to Internet, you can download a program called GrabKick from Aminet. That will extract a file which you can then transfer to the PC.

The alternative is to buy the ROM from Cloanto, the current distributors. Their Amiga Forever package is a very good purchase; they offer various software and ROM packages as well as a complete easy to use Amiga environment at a very reasonable price. We're going to try a different approach to theirs for this tutorial, however, so if you buy their CD, don't bother installing the whole package.

FS-UAE

We're going to use an emulator, and when it comes to the Amiga, there's really only one: UAE. The acronym is commonly interpreted to mean Universal Amiga Emulator, but it originally stood for the Unusable Amiga Emulator, due to its inability to even boot. Further refinement provided the features theretofore missing. With the introduction of just-in-time compiling it got a hefty speed boost, and UAE today is fast enough to emulate Amigas with PowerPC accelerators and GPUs while still remaining cycle-exact.

UAE comes in different flavors, one of which is called FS-UAE. The FS part is the GUI built on top of UAE, and for my money it's a far more uncluttered and usable experience than WinUAE. As a bonus, it is available for major Linux flavors as well as Windows, and behaves identically between platforms. Download FS-UAE and install it according to these instructions (with the current version, you no longer need to edit the config files).

The first thing you need to do is to import the kickstarts. By clicking the top left icon, you will see a menu. Here, you either select Import Kickstarts... (if you extracted a free-standing kick-rom file) or Amiga Forever Import... if using Amiga Forever. Next, under Amiga Model, select A1200 and the appropriate ROM configuration (either 3.0 or 3.1/020 will do fine). Under Joystick & Mouse Port, select No Host Device for the joystick -- this will allow you to use the arrow keys when coding. Finally, register and save this as your configuration (left-hand list box).

Next, in the tab list, click on the tab icon that looks like a black chip. This takes you to the Kickstart ROM tab. Here, select Custom and choose your kick-rom file. You may also tick "Zorro II Fast RAM" - select the largest amount. Save configuration.

Now, click on the floppy icon in the tab list. This allows you to uncheck (and thus activate) all four potential floppy drives, which we will do for the sake of convenience. More important is the Media Swap List; FS-UAE requires you to add all floppies you can use beforehand. Click the plus sign, then select all the Workbench 3.x disks.

So far, we've set up a fairly standardized Amiga 1200 with some extra peripherals. However, there's one thing missing that we really need: a hard disk. Click the main menu (top left tab icon). From the menu, select HDF Creator... and create a non-partitioned HD file which you call System (a size of 60 MB should be enough). This creates a file that acts as a hard drive. Select the Hard Drives tab, and pick the file you just created.

Now, start FS-UAE with the Workbench disk in you primary floppy drive. Boot it up. You'll see your hard drive as an unformatted non-Dos disk. Click on it, select Format from the menu, using FFS (Fast File System) with no trash can. Format. Now, load the Install disk into DF1:, and Locale and Extras in the other two. Double-click on the Install disk, then on the Install Workbench icon. In the installer, select intermediate level, and when it comes to installation directory, select your System hard drive (for some stupid reason, the default is DF0:!). Installation should prompt you for disks as they are needed. Once you're done, Workbench 3.x will have been installed.

Configuring Workbench

The first thing you need to do is close down the Amiga. We need some way to get files onto the machine, and the easiest way is for you to mount a second hard drive under the hard drives tab. Instead of mounting a hard file, you can mount a Windows or Linux directory. I usually find it simplest just to mount the Downloads folder. Now you can freely move files between your main computer and onto the Amiga. Workbench will treat it as if it's a regular hard drive (as long as you select "show hidden files" from the menu).

Workbench is pretty well set up for serious work right off the bat, but there are a few things it lacks. Its greatest Achilles' Heel is arguably the lack of a decent command line interface. While the default CLI is leagues beyond MS-DOS, that's really damning with faint praise. To fix this, we're going to download KingCON (also known as Newshell) off of Aminet. KingCON is unfortunately packed in lha format. You can either use a free utility like 7-zip to open it up on the PC, or download Lha from Aminet. If you do the latter, move Lha.run to RAM:, execute the file there, then copy the archiver (called lha_68020) to the System:C/ folder. The other files are unnecessary.

Next, move KingCON_1.3 to RAM: and unpack it there. Execute the installer, and follow the instructions (basically, you enter the cli, type "ed s:user-startup", change KRAW and KCON to RAW and CON, and add the unmount CON: / unmount RAW: commands as it directs).

Slightly complicated? Perhaps. On balance, I think the new CLI (which lets you use the TAB key to autocomplete or choose files from inside a file requester) is easily worth the small hassle of installation.

Back up the hard-file; we're almost done.

Making it pretty (optional)

Workbench does look a bit drab. Nothing that can't be fixed, however -- all you need is to download Magic User Interface and MagicWB. Copy them to RAM: as usual, and then install.

Conclusion

You should now have an Amiga WB environment up and running. I've tried to keep my tutorial as general as possible, so I've avoided actual programming environments, DirOpus, graphics editors like DPaint, et cetera. There's a ton of useful software to that effect, and I'll mention others when needed.

This has been a primer on how to painlessly set up an emulated Amiga environment. I hope you liked it and will, as always, be grateful for feedback.

On (Recursion (Recursion (Recursion ...

Hello everyone! I had an Amiga article all planned and ready, but since I couldn't make up my mind on the exact restrictions, I kept putting it off. Enough is enough. Now I found myself with a rather stream-of-conscious take on a common programming technique. To wit, it's about the use of recursion, and my struggle to make intuitive sense of it.

So, without further ado, here we go.

On recursion

The effective exploitation of his powers of abstraction must be regarded as one of the most vital activities of a competent programmer.
--Edsger W. Dijkstra

What's the best way to understand recursion? As the old joke has it, you must first learn recursion. Proponents of this technique claim it is an intuitively obvious, far-simpler way of iteration compared to the more popular imperative ones, and that it's only our mindset (maimed as it is by earlier exposure to imperative programming) that has us thinking otherwise.

Personally, I think that's a crock of shit. We all know recursion isn't simple, otherwise the joke would make no sense.

Holding up recursion as some sort of replacement for iteration is also bullshit. Loops are good. For-loops are okay. While-loops are good. All of them work in place of recursion, but that doesn't make them the same. They handle iteration differently. They have different strengths. They are separate idioms. And so, as in all programming, they require separate metaphors to be properly explained.

Now, it's no wonder that imperative programmers are used to while loops: it's built into our metaphor about how programs are supposed to execute. Recursion, though, requires us to revise our expectations. Loops are like a moving watch, with hands (numbers) that increase in proportion to each other, one sometimes triggering an alarm (a specific method call) or clicks over into a new state. So what makes a useful recursion metaphor?

Well... for me, recursion is all about what you see from where you are.

Traditional loops are flat. We see everything as one big field of similar items, or a big mass of numbers. All of these numbers are operated on by the loop, so we need to understand them and their interactions as a gestalt, as a whole. If we don't understand everything about the loop and the data on which it operates, the loop will at some point go off the rails. Those are a lot of factors for a programmer to juggle.

Recursion is different. In a proper recursive algorithm, your data is a structure, a grid. The shape of the grid doesn't really matter: all that matters is what happens on your immediate position on the grid. All you need to remember is that once you step one level up and down in the recursion, you are in effect moving along the grid. That's intrinsic to the structure, to the algorithm's idiom, so you don't need to keep track of it. All you need is to understand what happens at the specific point you occupy.

To me, where the metaphor of regular loop suggests enumeration, the metaphor of recursion suggests traversal. A regular loop chews through items on a level playing field. Recursion moves from node to node, like a spider flitting across a web. That makes recursion a natural fit for things that have tree-like behavior, but less ideal for things like iterating across flat containers. It also means the node is all you need to care about, which means less cognitive work.

Recursion can replace loops in a pinch, yes. By the same token, a wrench can do the work of a hammer. That doesn't make it the best tool for the job.

Perhaps I'm still poisoned by imperative thinking. It may be that Dijkstra, from whatever coder heaven he now resides, is even now shaking his head and muttering something about the irreparable damage of BASIC. Nevertheless, and this may sound paradoxical, I think recursion is even more useful if placed in constraints. And when it comes to coding, perhaps an abundance of metaphors isn't such a bad thing.

That's it for now. If you still have problems wrapping your head around recursion, I refer you to this article.