8 Mb CHIP RAM on All Amigas

[xeron]

But I believe it is possible.

Then you are wrong.

Ok then, it is time to create UAE for Amiga....to emulate the 32 bit needed for the chipRAM and have the rest of the emulation for everything else run natively

The problem is this: The chipset requires that any bitmap that is displayed or blitted, and any sound samples must be in physical chip ram. The chips that create the display and output the sound have a physical limitation on the amount of memory they can actually read. They have no memory mapping unit, they just have a memory bus that is limited to 512Kb, 1Mb or 2Mb depending on which revision. This limitation is to do with physical pins on physical chips and wires between them. To increase the amount of chip memory, you'd have to make a new revision of the Amiga chipset with extra chip ram address pins, and make a new motherboard to use them.

To emulate 8Mb chip ram on the Amiga, you have to emulate the whole Amiga chipset, and the 68k just isn't fast enough to do that, especially emulating AGA on AGA would be really slow, and actually really crap since you'd be limited to 256 colours (or possibly you could use HAM-8, but you're talking minutes per frame here now, rather than frames per second). You can't emulate 8Mb chip ram and expect the real chipset to use the emulated chip ram, because they physically cannot address that much ram. To them there isn't that much ram in the whole world.

since it is a real Amiga.............keeping everything still running smooth :-)

No. Its not possible.

Then if it is not possible without a gfx card....it is possible with one as we already know

No. An A1200 with a 32Mb gfx card still only has 2Mb chip ram. The Amiga chipset can't directly access any RAM on the gfx card at all. The graphics chipset on the graphics card can't access the amigas chip ram usually either.

Well then....one will have to be created to take care of that :-)

What? A piece of code that physically adds pins to chips and tracks to motherboards?

 If you had an MMU I guess you could use the Fast ram as "virtual" chip ram in the same way it would normally use HD

Ah......now we are getting somewhere :-)  thanks for open mindedness :-)

Nope, you're not getting anywhere. It is simply not possible to get the chipset to see outside of chip ram, it is physically directly attached to chip ram and not through any kind of memory management unit. No amount of software can fix this.

[xeron]

At the end of the day, an 8Mb Alice would only be able to see 8Mb in an A4000, since its the only Amiga motherboard in existance with enough address pins wired to the Alice chip.

Leirbag, just face it. The only things that would get you 8Mb of chip ram in any way compatible to existing amiga os & apps are:

1) Run UAE

2) Make an 8Mb Alice (and possibly revised other chips), and put them in an A4000

3) Emulate the whole chipset on the 68k (which is basically 1)

And thats it. All of the "so-called" impossible things you mentioned (memory cards, USB etc.) were feasible if someone came up with the hardware and drivers to do it. 8Mb chip ram is something different.

With appropriate glue hardware you can interface pretty much any peripheral to an Amiga (or C64, or anything with some IO ports). You could add a firewire port to a ZX81, but it wouldn't actually be useful ;-) ). But 8Mb chip ram just isn't possible in the way you want it to be done. It just isn't.

In fact, i'll say this. If you don't want to run AmigaOS, or any Amiga apps on it, you can add terabytes of chip ram to an Amiga. Its easy, you just put a PCB on the motherboard over the chip ram chips that has address decode logic that includes banking. Lets say, for example, writing a number between 0 and 4294967295 to address $C banks in a different 1Mb bank into the upper 1Mb of chip ram address space, and you actually had that much RAM on the board. Thats more than 4000 terabytes of chip ram.

Great. Except that AmigaOS and its apps simply would not be able to use it. You'd have to patch amiga os, and pretty much rewrite all of your software. It just wouldn't work. So get over it.

Edit: And before you say "Great! We've just got to fix the problem with software compatibility and its solved!", don't. Fixing it is more work than it gains you.

You'd have to change exec to remember the upper memory bank number for every task. That parts easy and has almost no speed penalty.

The problem is that AmigaOS and its apps expect to be able to pass memory pointers to each other. Now, you could pass 64bit pointers instead of 32 (32bit address, 32bit chip bank), but now you have to patch _every_ single Amiga application individually that you want to run, because every single amiga app and API uses 32 bit addresses, and you wouldn't be able to run a single existing binary natively without modification.

[xeron]

Workbench believes whatever exec tells it. If AvailMem( MEMF_CHIP ) returned 128Mb, workbench would say you had that much chip memory. I could write a patch right now that did that. You'd still not have more than 2mb chip ram, though.

[xeron]

Any suggestions of using MiniMig to create a replacement chipset for an existing Amiga motherboard won't come to anything, either. The schematics are not available for the chipset, and the MiniMig doesn't aim to emulate the chipset at a hardware level. It really only emulates the chipset at a register level so AmigaOS can run on it.

[xeron]

@Tricky

Basically, for your "4 banks of chipram" approach to work, you'd have to have 4 completely independant instances of AmigaOS running, 3 of which are suspended.

The problem I see with this, is DOS. Imagine if you swapped instances while someone was accessing the disk. In the new instance, you delete some files, maybe even files that were open on the other instance.

Whoops! You've just corrupted your hard disk.