Emulation, or Replication?
Is there any essential difference between an emulator and a hardware clone? What should it mean to “clone” a computer system? These questions have been on my mind a lot recently, as I work on my Mac Plus clone, somewhat calling into question the whole point of the project.
The retrocomputing world is full of emulators for popular computers of the past. These emulators are software programs that run on a modern PC, providing the user with the same experience they’d get on the real computer. While some emulators may require a ROM data file from the original machine, they are still pure software solutions, requiring no special hardware. In the Mac world, programs like Mini vMac, Basilisk II, and Sheepshaver fall into this category.
Less common are hardware replicas or clones of classic computers. These are physical pieces of hardware that you need to build or buy, and that function just like the classic computer they’re based on. This category can be broken down further into what I’ll call physical replicas and functional replicas. A physical replica uses most or all of the same hardware as the original machine, and provides all the same I/O options, allowing for the attachment of vintage peripherals. The Replica 1 copy of the Apple I is a good example. A functional replica, on the other hand, works like the original machine but is not built like one. It probably contains an FPGA or microcontroller, and uses modern I/O devices like USB or PS/2 mice/keyboards, VGA monitors, and memory cards. Plus Too falls into this category, as does the Minimig Amiga replica.
Traditionally it wasn’t possible to emulate another computer at full speed, because the overhead imposed by emulation demanded a host computer that was several times faster than the computer being emulated. However, given the tremendous power of modern computers compared to 1980’s vintage machines, full speed emulation of classic computers is now common. Physical replicas still have their place too, where you want to work with real vintage peripherals.
What then is the place for functional replicas? I’m not sure there is a good one. If I finish Plus Too and put it in a nice box, it will look like a Mac Plus on a VGA monitor, with a PS/2 keyboard and mouse. But if I put a small form-factor Windows machine in a nice box and run Mini vMac on it in full-screen mode, it will look identical. So what if one is a “hardware clone” and one is an emulator– from outside the box, there will be no way to tell the difference. Is the hardware clone cheaper? Doubtful. More compatible? Possibly, but Mini vMac is compatible with virtually all classic Mac software. More portable? More hackable? Perhaps.
It’s all a little discouraging to think about. I don’t think it’ll stop me from working on the project, because it’s been a fascinating learning experience so far. But it does make me wish for some ways I could distinguish Plus Too from a pure software emulator. Maybe I need to reconsider the use of vintage Mac peripherals, although that would certainly make the project a lot more challenging. Or maybe there’s another interesting way to emphasize the hardware aspect. If you’ve got a good idea, please post it in the comments. Thanks!
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One difference between a functional replica and a software emulator is bootup times.
If you turn on a functional replica, you will start the bootup sequence of the replicated device immediately.
If you turn on a PC running a software emulator, you will first need to complete the host OS bootup, before you start the bootup sequence of the emulated device .
I’m really enjoying your posts about the whole Plus Too design and your thoughts on the whole process. I really hope that you won’t talk yourself out of it…
One significant advantage of the functional replica over the software emulator is the whole learning process, both for you and for us. I built Vince’s Replica 1 and learned a lot in the process. I’m looking forward to learning about the Mac Plus through your efforts on building the clone. I would happily contribute, and would definitely attempt to build one.
Building a dedicated modern machine to run the emulator may look the same on the outside, but we won’t have learned much in the process and we will know that it’s boring inside.
I’m all for creating emulators, they are a great learning process in themselves. I just don’t think that it’s in the same category, and the hardware route is significantly more interesting. An emulator feels like step 1 to me. Now you understand the target, you’ve got to build it.
As for the relative merits of a physical replica and a functional replica, that’s a tougher question. Choosing one over the other is a question of what motivates you for this particular project. A modern, functional solution feels more approachable to me, at least in terms of trying to build it from the design into a product I can actually use in the end. Needing an original Mac Plus keyboard, say, could be a significant hurdle. Having the option to use either the vintage peripherals or modern replacements would be ideal.
Let me paraphrase: “To hardware or not to hardware ?” 🙂
The real question is: What makes you more happy ? Writing software or making real hardware.
You can drive car replica on the road or drive it with the perfect software simulator with panoramic 3-D screens. What is better ? There is no simple answer.
Personally, I feel like the end result of building hardware is more tangible. I can show it to friends and, even if they don’t understand it, they can see that I made something that not many people can. Writing software can be just as much work, but the end result is another file on the computer that’s hard to tell at a glance if it’s any more or less complex than any other file.
If you’re looking for something to make the hardware distinctive over software only emulation, go ahead and implement a compatible floppy disk drive. Variable data rate with constant rotational speed should give the same results as constant data rate with variable rotational speed, if you want to use a modern floppy drive.
None of this has any use. Nobody needs either an emulated ancient apple computer or a rebuilt hardware one. So forget about what’s the easiest solution and make what is _fun_.
This project looks a great deal of fun, and I imagine there will be lots of satisfaction when you see something working that wouldn’t be there from an emulator. Emulators were cool when they were new, or few a new machine, but few people can make replacement hardware like this, and it’s a much more exciting project.
I think it would be cool if you could replace the innards of an old Macintosh with the newer, more readily available hardware. Especially if you have the best of both worlds, old connectors for peripherals from back in the day, new connectors for modern peripherals (ethernet, serial, USB keyboards/mice, SD card for storage). You could still read old floppies and get on the internet with it, and it could have the option to run faster or have more memory.
The DIY vacuum forming method the guys at Ben Heck’s forum use would give the project a lot of possibilities for new form factors, like a laptop or palmtop with a low resolution LCD display.
I’ve had to get rid of old broken Macintoshes, I can’t get parts for them anymore. You hear the chime of death, then what?
Besides playing games, I still like to use my remaining working SE as a word processor, it’s a great distraction free place to just write. Maybe there’s still a place in the world for just a simpler work environment I can’t switch out of (like an emulator would allow).
One word that will haunt all software for all time: obsolence! Ditto for the original hardware.
An open hardware project like this is bound to have a much longer lifespan than any software emulator will. (Mini) vMac has already been ported from classic MacOS to Mac OS X to Intel Mac OS X.
I don’t regret getting rid of old Macs or having zero classic Macs because of the hassle–upkeep, swapping files between old and new machines, and so on. A project like this checks off a whole bunch of boxes for me… if you end up producing a kit, sign me up for two. 🙂