Hyperion Entertainment: Clarification of Current Situation

[guest11527]

The 68k architecture supports an address speace that is up to 32bit bit wide, meaning up to 4GB. AmigaOS also supports 32bit memory addressing, however many of those addresses are reserved (chipram, various I/O) and cannot be used as FastRAM for the CPU, which practically reduces the ammount of possible FastRAM to 2GB.

Well, not quite. The address space taken up by motherboard resources is much less than 2GB. The lower 16MB are pretty much everything, and you may add some parts of Zorro-III space if you like, but that neither fills 2GB.  

The problem is rather the exec function AllocEntry(), which reserves bit 31 as error indicator and hence cannot handle more than 2GB RAM.

Or rather: Almost. Everything beyond this function is pretty much 2GB-safe, so in principle one could even add memory beyond the 2GB limit as long as AllocEntry() has never a chance to access it - it wouldn't be hard to modify the function accordingly. With this small adjustment in mind, the limit is more like 3.5GB. Not that anything on AmigaOs would actually require this amount of memory in first place.

[kolla]

@ Kolla Have you tried one of the smaller Linux distros? You can get Xfce desktop which is lot like you asked for.

Of course I have. Just to be clear, I have worked professionally with linux in various incarnations for more than a decade, I have maintained my own patch set for the linux kernel for a long time, I have buildt from scratch and maintained two Linux distributions, one for m68k and one for bigendian ARM, I was maintaining and patching KDE3 and Qt3 on my own before TDE showed up... I pretty much know Linux in and out at this point, though the entire systemd hoople may throw me back to BSD.

And look at the points I wrote, Linux do not offer any of them, not even close, I really do not understand how you guys can suggest Linux. Xfce does not offer one single thing of what I listed up (and besides I cannot stand GTK, and prefer LxQt over Xfce any day).

[kolla]

Iggy, are you reading what Thomas is writing? OS4 suffers from the exact same limitations, which was my entire point. Now, of course you can do funny tricks to support more RAM on OS4, but same tricks also can work for OS3, and who knows, maybe Gunnar will decide to make Phoenix with 64bit memory addressing and someone with skills and resources updates exec and whatever else in OS3 to support this. But noone seems willing to deal with the real issues of AmigaOS, which all boils down to memory management, protection, security and networking.

[ElPolloDiabl]

@kolla
AROS makes a clean break from legacy. Someone just needs to modify it to how you like it.

[psxphill]

How much RAM can a modern 68SEC000 (which is the one produced still) address?

The 68SEC000 can address 16 megabytes. It's not modern, it's a static version of the 68000.
 
 It would probably be safest to add 2gb of ram and map it from $00000000-$7fffffff, but knock holes in it for chip ram, custom chips, zorro ii/iii cards etc. So you wouldn't actually have 2gb of ram (a lot of PC's suffer with this problem when adding 4gb, especially if you run a 32 bit os).
 
 It wouldn't surprise me if there were more problems than AllocEntry (which would have to completely skip ram above 2gb). There were enough problems with info and installer once you added a 2gb drive for instance.

[kolla]

@kolla
AROS makes a clean break from legacy. Someone just needs to modify it to how you like it.

No, AROS makes no clear break from legacy, on contrary, its main focus and goal is being legacy compatible.

[Rob]

No, AROS makes no clear break from legacy, on contrary, its main focus and goal is being legacy compatible.

AROS is only legacy compatible on 68k.  Elsewhere it is only API compatible so no reason not to fork it with any break from compatibility.

[OlafS3]

AROS is only legacy compatible on 68k.  Elsewhere it is only API compatible so no reason not to fork it with any break from compatibility.

He wants a completely new OS that breaks compatibility but has modern features. But which sense makes a OS without software? :confused:

It is a kind "showing what is possible" but for me the practical value would be limited

[kolla]

I didn't say there would be no software, by providing a functional and compliant posix layer, you already have plenty of software ready. By offering a platform rich with tools to develop with, a solid foundation to develop on, and very few strings attached, software will emerge.

[guest11527]

It wouldn't surprise me if there were more problems than AllocEntry (which would have to completely skip ram above 2gb). There were enough problems with info and installer once you added a 2gb drive for instance.

Well, what individual programs do about it is of course another issue. I'm only talking about the Os. AllocEntry() has a problem, and the kicktag list for resident modules has the same issue (it uses bit 31 as a flag). While not identical, the issue is related. The kickmemptr structure follows the same convention than that of AllocEntry() (it is in reality not allocated through AllocEntry(), even though it looks as if it is.)  Individual programs can fail because they erraneously read the memory size as signed integer rather than unsigned integer. Even though AvailMem() and friends clearly return an ULONG and not a LONG, but who reads documentation anyhow...

[guest11527]

My understanding of things...

The 68k architecture supports an address speace that is up to 32bit bit wide, meaning up to 4GB. AmigaOS also supports 32bit memory addressing, however many of those addresses are reserved (chipram, various I/O) and cannot be used as FastRAM for the CPU, which practically reduces the ammount of possible FastRAM to 2GB. And this is the same limitation, whether you are running OS3 or OS4.

I am not sure what you are asking, but someone could make 68k processor card with 2GB (gigabyte - Gb is gigabit, 2Gb would be 256MB) and AmigaOS should run fine, yes. I don't have access to WinUAE here, but how much system RAM is it possible to add to a system config in WinUAE?

Well, in reality I don't agree that the physical limitation is really the problem. It isn't hard to create a CPU with 32 bit logical address space but a physical address space that is much wider. After all, intel did the same, called it PAE... It requires a bit of MMU trickery to do that, and of course a CPU with more physical address lines than logical address lines is possible.

The problem lies elsewere: The problem is that, on such a machine, programs would be required to distinguish between logical and physical addresses, and would be required to use Os interfaces properly. Or interfaces that are close to the Os. Or whatever you all them. Apparently, this is not "en vouge" in the Amiga community, i.e. to use other's interfaces. I already hear people screaming "dictatorship!" if I come up with such ideas. So one way or another, it wouldn't happen. The wall is in the head, not in the hardware.

[Rob]

He wants a completely new OS that breaks compatibility but has modern features. But which sense makes a OS without software? :confused:

It is a kind "showing what is possible" but for me the practical value would be limited

That was AROS x86 once.  Most AROS software is open source so if you branch AROS to support SMP, memory prrotection and so on you can probably adapt most of the software in a much shorter than it took to port to AROS in the first place.

[itix]

The problem lies elsewere: The problem is that, on such a machine, programs would be required to distinguish between logical and physical addresses, and would be required to use Os interfaces properly. Or interfaces that are close to the Os. Or whatever you all them.

What OS interfaces you use when there is none? AmigaOS is a low level operating system with very little abstraction.

[kolla]

Now, if only it was possible to get anywhere near the max RAM limits with the Vampire boards, haha. Oh well, so many conflicting ideas and interests.

[guest11527]

What OS interfaces you use when there is none? AmigaOS is a low level operating system with very little abstraction.

There are.... at least as far as memory remapping is concerned.

[itix]

There are.... at least as far as memory remapping is concerned.

Uhm. .. like what?