Storm in a Pi Cup

If you want a rollercoaster ride, take a look at the graph of “Amiga Accelerator prices over time”. What was once in stock in every magazine advert at RRP, then became so cheap you’d be literally giving them away. But for whatever reason prices started to grow and grow until you’d be paying far more than the original price. And that’s where we find ourselves now, with even a simple upgrade often costing more than the Amiga it sits in; as an example a Blizzard 1230 board which had an RRP of £279 in 1993 will now set you back over £400 and the price is climbing. For an A500 owner, a GVP A530 sidecar for an A500 is well over the 1990s RRP of £299 and likely still features a vintage SCSI drive, probably close to failure.

Vintage GVP A530 expansion; SCSI hard drive plus 68030 processor for the A500

So is it all out of reach? Well not if you think a bit laterally and that’s exactly what Claude Schwarz has done with the PiStorm project. Whilst the Motorola 680×0 processors used in Amigas have long been out of production and are getting rare in the quantities you’d need to build a new accelerator, there are many more powerful processors available for a fraction of the cost, in numbers that an Amiga project would barely make a dent in. The best example is the ARM processor in the ubiquitous Raspberry Pi, and it’s Claude’s genius that joins this low power, fast, affordable single board computer to an Amiga and gets it running 680×0 code to the point that the Amiga doesn’t know any different. That’s correct; the PiStorm is a Pi-powered, Amiga accelerator that swaps the rare 680×0 chip for an ARM chip in a 680×0 disguise.

That’s correct; the PiStorm is a Pi-powered, Amiga accelerator that swaps the rare 680×0 chip for an ARM chip in a 680×0 disguise.

It’s a simple concept when you think about it. The processor in a computer responds to combinations of signals on input pins, and outputs the “result”. A Raspberry Pi has a bunch of IO pins and can compute a result from the input it receives. At that point, they’re identical! Claude’s hard work went towards translating the 68k instruction set and emulating it on the Pi so it responds in exactly the same way as a 68000 CPU would and to accomplish this there’s a software emulator on the Pi which takes the 68k instructions, runs code on the ARM processor on the Pi, and then spits out the 68k result as though a real Motorola chip had done it. There’s also a translator board, as there are fewer IO pins on a Pi as you’d have on the real CPU, but what you don’t have is a huge expanse of logic, memory, connectors and components like you’d see on a traditional accelerator. All that uses the famous Raspberry Pi miniaturisation; it was after all the first mass-market tiny computer.

So the end result of this is a plug-in module that replaces the 68000 accelerator in an A500 and provides a speed equivalent to around a 60MHz 68030, for around £50 including the Pi. That’s less than a third of the price of a modern A500 accelerator like the Terriblefire TF536, but there’s some more surprises in store that can make it a truely unbeatable proposition.

  • Firstly, the Pi has a whole chunk of memory just sitting around doing nothing and this is passed through to the Amiga as 128MB of Zorro3 FastRAM. Imagine in 1990 being able to afford that much, even if you had a board that supported it. In a world where we’re used to 8MB expansions being good enough to get by on, it’s an almost unbelievable amount.
  • Most popular cards like the TerribleFire, Matze TK and so on include an IDE port to add some sort of storage; CompactFlash, SD or even a real hard drive if your ears long for the continuous drone of spinning rust. Whilst that could possibly be done here, what Claude has done is just use files on the SD card the Pi stores its operating system on. Drop a HDF (Hard Drive File) on it straight out of WinUAE, and your Amiga boots off it after some simple configuration. No need for an adaptor, cables, finding somewhere to poke the card through the case, or even cutting holes. You know who you are! If you’re thinking that might not be the best idea as you may want to swap the image for a new one, absolutely, but that’s fine because the next point is…
  • It’s all controlled remotely from WiFi. There’s no jumpers, no flashing or uploading. There’s a config file with the options in, and you can edit that over SSH from a PC or a phone. You can even upload a new HDF file if you wish, without opening the case. Make a change, reboot, the change is applied.
  • It can load your choice of kickstart from the SD card, so if you’ve just bought AmigaOS3.2 and haven’t got a programmer, just load the ROM files onto the MicroSD card and set them in the configuration file. And as it loads from the first boot, there’s no rebooting like you’d get with a MapROM type program.
  • That’s about it. Oh wait, no there was one more. Retargetable Graphics (RTG). Yeah, sorry – nearly forgot, it’s got a graphics system using the HDMI output that will blow any traditional Amiga card into the weeds. If you want 24 bit high definition Workbench on that A500 your brother gave you back in 1993, this will make it happen.

So a quick recap. For the cost of a good meal out for two, you’ve got an expansion that lifts almost all the restrictions of the A500 in its stock form – speed, memory, storage and graphics all sorted in one affordable package. If you felt that you couldn’t use the A500 for productivity and it was just a games machine, the PiStorm will change your mind.

Is it the perfect solution? No, there are some downsides. Firstly you’re waiting for your “processor” to “boot” (and it’s literally doing just that; if you connect a monitor to the Pi’s HDMI connector you’ll see the familiar Pi startup process) so there’s a delay between turning your Amiga on and it starting up. In this respect there’s some work happening to tweak the configuration, but it’s really not a massive issue. Secondly, it’s not plug and play. You’ll need some level of Linux knowhow to set up the Pi, and follow the instructions to download, build, configure and run the emulator. Thirdly, and perhaps importantly, it’s not an Amiga accelerator in the true sense of the word to some people. If you’re a collector, if you love finding original hardware, then you may have a bit of a sour taste in your mouth when reading about a Pi “faking it”. This is not a boxed GVP A530 or Mega Midget Racer and it may not have the same appeal to an enthusiast, or someone trying to relive their past. But it definitely does what it sets out to do, which is to give an Amiga 500 a decent turn of speed and some important expansions, and it does it at a great price. And it’s interesting to note that a PiStorm could be considered impure as it’s not a 680×0 chip, but the Phase5 PPC cards of the 1990s with a similarly alien processor are now attracting a phenomenal price (admittedly accomplishing their task in a different way).

It’s certianly worth a look; the Pi is reusable for other tasks if you don’t get on with the PiStorm so really you’re only down the cost of the PiStorm board itself. At the time of writing that is a slight issue, since the release coincided with a worldwide shortage of the programmable logic chips it uses so whilst it has a low typical cost, you could be paying a lot more right now as ebay scalpers hike the price up. The PiStorm site has a few choice words about that particular practice, and the prices are already relaxing a little.

What lies in store? Well as you’ve probably guessed, this fits into the 68000 socket which is only found on A500 models. The A2000 has one too, but there’s no clearance under the drives so you’ll need an adaptor to fit into the CPU slot – something that’s currently in the works. In theory it could also work on the A600, but that uses a surface mount 68000 so will need another solution again to attach the Pi to the board. It’s entirely possible that an A1200 board will be produced to put the Pi in the trapdoor slot, but further than that there’s not much point until the Pi gets a faster variant since the circa 60MHz 030 it pretends to be isn’t a huge upgrade over the 25MHz 68030 the A3000 and A4000 came with and uptake would be low given the smaller target audience, and the fact many A4000s were well equipped with 68040s from the factory.

If you fancy giving this a bash, you’ll need a Raspberry Pi Model 3A+. This is the model that fits without modification, and offers the best speed. You also need the PiStorm board, a MicroSD card with space for whatever size hard drive you want on top of the Pi operating system, and you’ll need an A500 or A500+. Then you just need to head over to https://github.com/captain-amygdala/pistorm and scroll down to the Quickstart guide.

We’re really excited about where this is going; whilst it’s not for everyone it does mean you don’t need deep pockets if you want to play with a faster machine and RTG. There’s hints of networking becoming possible via the Pi WiFi too, ticking yet another expensive expansion off the list.

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