MiniMig + PowerPC = OS4 Hardware for all

[Jethro_Tull]

Having read in the news how the lucky few with an accelerated Amiga will be finally enjoying OS4, a crazy idea came to mind.  Maybe I'm just stating the obvious, and just dreaming up something which is technically impossible, but wouldn't a Minimig with a PowerPC processor offer an an affordable and readily available platform for OS4 classic?  

Hyperion apparently cannot port OS4 to any other platform (be it SAM440, Effika or a PPC MacMini) due to the current court litigations, which won't be resolved anytime soon. But selling OS4 for Classic Amigas is seemingly not a problem.  So why not emulate the existing Classic Amigas with a powerPC accelerator and run OS4 for classics unmodified?  Obviously the Minimig would need to be revised with the addition of AGA emulation, an additional PowerPC CPU, additional RAM and addtional logic in the FPGA to emulate a Blizzard or CyberStorm accelerator.  

Not a trivial task by any means, but thanks to Dennis and his forward looking generosity, we already have the building blocks.  And if Dennis managed to create from scratch an Amiga emulator in about a year, I beleive other talented individuals in this community might be able to pull off a PowerPC based AGA emulator in a similar timeframe.  

In my opinion, having the community actively work on such a solution is always better then simply sitting still waiting for the current quagmire to settle.  If PowerPC MiniMig is indeed possible, it would offer a win-win solution both for Hyperion (who would obviously sell many more copies of OS4) and to Amiga hobbyists (who will be able to run OS4 without spending a fortune while relying on old hardware)

Jethro Tull

[AndrewBell]

Interesting idea. Probably wouldn't count as a classic Amiga as far as the license goes.

Here's a prediction: I bet Piru will say it's impossible, pointless, too much effort, or all 3.
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Raptor 700r

[downix]

The MiniMig's nowhere near that capability at this time.  You could, at best, use an A500's accelerator, and I don't think anyone has made a PPC card for the A500.

[Jethro_Tull]

Hi Downix.  My idea was first upgrade the MiniMig to the  capabilities of an A1200, by adding AGA emulation.  Just as Dennis replicated all the internal busses in the FPGA, the same could be done for the PPC Accelerator. The A1200's expansion bus and the Blizzard's PPC interfaces should all be implemented inside the FPGA.  I didn't mean to plug a real PPC into the Minimig but merely to emulate one.  Using an FPGA with an integrated PPC (such as the Xilinx Virtex) might be one possible solution.  

Having read your various posts on the Minimig, you're obviously pretty qualified to judge whether such a solution is viable, what kind of development work it involves and what components would be best for the job!  Your feedback might indeed show us how in practice this might be possible!

[Jethro_Tull]

Whether it counts as a classic dosen't really matter, as long as it can run an off the shelf, original copy of OS4!  The PowerPC-Minimig can be sold without OS4 and Kickstart, which the buyer would then obtain from Hyperion and Cloanto respectively.  In time, it might even be possible to emulate other machines or use it as a general small form factor board!

[AndrewBell]

Jethro_Tull wrote:
Whether it counts as a classic dosen't really matter, as long as it can run an off the shelf, original copy of OS4!  The PowerPC-Minimig can be sold without OS4 and Kickstart, which the buyer would then obtain from Hyperion and Cloanto respectively.  In time, it might even be possible to emulate other machines or use it as a general small form factor board!

So your idea is to make this address and register compatible with an A1200/BPPC or A4000/CSPPC. I didn't pick up on that. That would probably bring up other problems though, such as sourcing 603/604 processors.
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Ford Granada (North America) Picture

[Jethro_Tull]

I beleive we need to source processors which are merely PPC compatible, not perfect copies of the 603 or 604e.  Also, we probably don't need to emulate the Blizzard PPC accelerator perfectly, but just enough to run OS4, which at face value seems easier then emulating an entire Amiga, down the the chipset timing and all other nuisances.

While Dennis had to emulate an OCS Amiga perfectly in order to run the vast reportoire of Amiga games, this time we simply need to emulate a Blizzard just enough to run OS4 reliably.  Since OS4 runs on various other platfroms with a wide variety of processors (A1, MicroA1, CybertSorm, Blizzard etc) it is probably a lot more forgiving as regards emulation then many Amiga games and hardware hitting programs.  Indeed, emulating the general setup of the Blizzard PPC might be enough to get OS4 going!  

Anyone here who has intimate knowledge of how the Blizzard PPC works may help! Maybe explain how the GAL which interfaces the processors with the Amiga and RAM can be reverse engineered if need be?  Remember, the 68K series processors is not used by OS4, so it's just neeeded to boot the Minimig and pass control to the PPC.  

When Dennis announced his Minimig project on this site, I was one of the many sceptics who thought it was impossible to recreate such a complex machine as the Amiga, but I was gladly proven wrong, as increadible as this looked.  By comparison, the task of emulating a Blizzard PPC just enough to run OS4 seems definitly possible!

[AndrewBell]

We need to source processors which are merely compatible, not perfect copies. Also, we just need to emulate the Blizzard PPC accelerator just enough to run OS4, which at face value seems easier then emulating perfectly an entire Amiga, down the the chipset timing.

I read something recently about G5 processors not being suitable for BlizzardPPC emulation, something to do with it being 64 bit maybe. I don't know if the same applies to G3/G4/Freescale CPUs.

While Dennis had the to emulate an A500 perfectly in order to run the vast reportoire if Amiga games, which depended upon the MiniMig behaving EXACTLY like an A500, this time we simply need to emulate a Blizzard just enough to run OS4 reliably. I beleive, that since OS4 runs on a various platfroms (A1, MicroA1, CybertSorm, Blizzard etc) it is a lot more forgiving then most Amiga games and other hardware hitting programs. Indeed, emulating the general setup of the Blizzard PPC might be enough to get OS4 going!

How precisely you need to emulate depends on OS4. I would expect it to have some checks to prevent it from running on a Mac or PearPC. Remember that the A1 has a licensed ROM that is checked. Also, OS4 for Classic requires a 68K CPU for it's first boot.
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Vapir No2

[downix]

Jethro_Tull wrote:
Hi Downix.  My idea was first upgrade the MiniMig to the  capabilities of an A1200, by adding AGA emulation.  Just as Dennis replicated all the internal busses in the FPGA, the same could be done for the PPC Accelerator. The A1200's expansion bus and the Blizzard's PPC interfaces should all be implemented inside the FPGA.  I didn't mean to plug a real PPC into the Minimig but merely to emulate one.  Using an FPGA with an integrated PPC (such as the Xilinx Virtex) might be one possible solution.  

Having read your various posts on the Minimig, you're obviously pretty qualified to judge whether such a solution is viable, what kind of development work it involves and what components would be best for the job!  Your feedback might indeed show us how in practice this might be possible!

Using a Virtex would work, but be expensive.  Also, I don't think anyone beyond bPlan knows the details of how the accelerators actually worked.  I could theorize, but there's no guarantee that some minor feature won't cause OS4 to crash and burn.

But, it is possible.  Just very expensive for minimal gain.

[Jethro_Tull]

Why is the gain minimal?  Having a relativly inexpensive open platform for OS4 is definitly not a minimal gain!  I'm sure it did not appear a minimal gain for Dennis to replicate the cheapest, most widely available and least powerfull Amiga in an FPGA, but he went ahead and did it.  And as they say, the rest is history!  

Really, the alternative to the PowerPC-Minimig is either shell out a small fortune for old used hardware, buy a used discontinued A1 for a similarly high price or hope the current legal issues are resolved and wait for Hyperion to port OS4 to the SAM440.  None of the options sound better then having an open hardware platform for the existing, unmodified OS4 in my books!

[AndrewBell]

Really, the alternative is either shell out a small fortune for used hardware, buy a fragile and discontinued A1 or hope the current legal issues are resolved and wait for Hyperion to port OS4 to the SAM440. None of the options sound better then having an open hardware platform for existing, unmodified OS4 in my books!

Surely the easiest solution would be a piece of software similiar to Mac-on-Linux. Then you could run it on existing Mac hardware.
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STARCRAFT II REPLAYS

[Jethro_Tull]

Indeed a software emulator which relies on a real CPU would also be an ideal solution!  MacMini Amithlon anyone?  it seems ACube already had some working prototype up and running.  Maybe they could team up with Cloanto (they're both Italian after all) and release AmigaPPC Forever OS4, what a mouthfull!  

Again, I'm asking the technical guys here what are the chances of using open source PPC virtualisation software as the basis to run OS4 on PPC Macs, such as the Mac Mini?  Although in the long run we'd still be stuck to buying second hand hardware to run OS4, at least it's readily available, cheaper and vastly more powefull then either the A1 or PPC Accelerators.  It also runs MacOS X, which must be the best OS known to man, excluding OS4 of course!

[AndrewBell]

Jethro_Tull wrote:
Indeed a software emulator which relies on a real CPU would also be an ideal solution!

Technically speaking, MoL is a "virtual machine", not an emulator.

it seems ACube already had some working prototype up and running.  Maybe they could team up with Cloanto (they're both Italian after all) and release AmigaPPC Forever OS4, what a mouthfull!

I think ACube actually got OS4 running on a Mac mini, which brings us back to the licensing issues. As for Cloanto, I think they just packaged WinUAE and OS3.9 together, as far as I know they haven't done any emulation coding.

MoL is open source, I think that would be the best place to start.
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Xxx Tube

[Jethro_Tull]

Thanks, I stand corrected on calling virtualisation an emulator.  However, if  OS4 Classic and the Amiga virtualisation software are sold seperatly, wouldn't that beat the licensing issues?  After all, OS4 Classic is sold  to run on classic hardware, no harm done from from Hyperion's part!  As for the Amiga virtualisaton software, it could be sold seperatly, without any of Amiga Inc's precious IP included, thus avoiding their wrath and sidestepping any licensing issues.  Cloanto, would simply supply the legal Kickstart files if they're needed to run OS4.

[AndrewBell]

Jethro_Tull wrote:
However, if  OS4 Classic and the Amiga virtualisation software are sold seperatly, wouldn't that beat the licensing issues?

That depends on the contract between Hyperion and AInc.

After all, OS4 is intended to run on classic hardware, no harm done from from Hyperion's part.  As for the Amiga virtualisaton software, it could be sold seperatly, without any of Amiga Inc's precious IP included, thus avoiding their wrath and sidestepping any licensing issues.  Cloanto, would simply supply the legal Kickstart files if they're needed to run OS4.

Again, it depends on the existing contract. I'm 100% certain that AInc wouldn't just accept the situation. An independent, open-source VM would be harder to pursue in the courts though.
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SUZUKI X-90