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Information about the Apollo CPU and FPU.

The 64 Bit K Questions?

Thierry Atheist

Posts 644
15 Oct 2016 07:47


I'm an inventor. I'm an AMIGA fanatic.... You can tell that by reading any 5 or 6 random posts I've made here (or anywhere else).

So, I'm still obsessed by this.

The Vampire 2 (Apollo cored AMIGA) has 64 bit instructions now. So, does it mean that somehow we could break the 2 Gigabyte ram address space barrier?

I was thinking something like;

First 2^31 addresses used as normal
2^31+1 to 2^32 never referenced
2^32+1 to 2^64 accessible by the fact that 64 bit capable instructions can be executed now!!!!

So, using that method, we would be able to use 2^64-2^31 RAM addresses.... How COOL would THAT be????


Samuel Crow

Posts 424
15 Oct 2016 10:04


Maybe someday.  We currently do not have enough pins on the FPGA for that amount of addressing, nor do we have space for 64 bit immediate values in the current instruction set, nor do we have room in the instructions for a huge register size.
 
  Maybe we will get there someday but it is more important to get ported to AROS now so that we can create a 64-bit enhanced mode for the 68090 since AmigaOS 3 doesn't support 64-bit addressing modes.

Lastly, the negative 32-bit address space is used by some PCI bus boards for I/O.


Thierry Atheist

Posts 644
15 Oct 2016 10:21


Hi Samuel Crow.

Thanks for replying (to my probably bizarre requests).... The more I read about CPUs.... the less I understand them!

So, I guess that the Arria 10 would have that same problem too, then?

What about the custom graphics chipset? For instance, I've only found out about 2 to 3 years ago that they were 16 bit, and was even way more shocked to find out that OCS, ECS AND AGA ran at a mere pathetic 3.5 MHz!!!!

Except for Agnus, could the other chips, OCS or ECS or AGA be converted to 64 bits? Or would that destroy backwards compatibility? I ask, because the graphics cards on intel motherboards, they've made those 64 bit, then 128, and they're using 256 now.... Totally don't understand that, but it works, doesn't it?

Also, could AMIGA's graphic custom chip be used for GP and CUDA like people are doing with nVidia graphics cards?


Gunnar von Boehn
(Apollo Team Member)
Posts 6207
15 Oct 2016 12:34


The FPGA or CPU are not the limit. The limit is the AMIGA OS.

AMIGA OS does simply not support 4 GB or more memory.
But frankly, this is not a problem.

For typical AMIGA applications 512 MB or 1 GB is pretty close to "infinite" amount of memory.



Thierry Atheist

Posts 644
15 Oct 2016 12:54


Thanks Gunnar.

I just thought that it could be circumvented (the barrier) at the assembler coding level.

I am getting one standalone FOR CERTAIN, and hope that I can get 2 more after that.

Thank you VERY MUCH for this project you're working on....

That is the ENTIRE TEAM working on it, as well.


Ian Parsons

Posts 230
15 Oct 2016 18:07


The Motorola design team were very forward thinking in using 32 bit address registers at a time when the norm was usually only 16 bits.  When it came to packaging the design in the 68000 a 24 bit address range for the external bus was considered plenty (RAM was still so expensive that 128k was considered for the first Amigas like used on the first Apple Macs). Over 30 years on and most devices still have 32 or less bits worth of addressing RAM installed.


Samuel Crow

Posts 424
17 Oct 2016 04:58


AROS has a 64-bit version but only for AMD64 at this point.  The problem is that it won't be backward compatible with the 32-bit version even if it would be rewritten.

posts 7