64bit: "This interpreter (vers. 68000) cannot read image file (vers. 274877913446)."

64 bit images are rare, unappreciated, and poorly supported (all Squeak
images of practical interest are 32 bit images with 32 bit object memory
word size). However, 64 bit VMs are commonplace and work quite well on
hardware and operating systems such as yours. You may need to load the
changes on Mantis bug report 5688, and check Mantis for other issues in
the "Squeak 64 bit" category if you run into problems, but other than
that a 64 bit VM built on your system should work fine and should run
normal 32 bit images without problems.

Andrew Gaylard wrote:
>
> - For which hardware/OS combinations is there a 64-bit VM?
> - Does this VM run both 32-bit and 64-bit images?
> - How do I convert a 32-bit image to a 64-bit one?
> - My OS allows a single process to grow to 3.75GB ; if I need a lot of
>   objects can I use a 32-bit image / VM, or must I use a 64-bit one?
> - What are the advantages/disadvantages to using 64-bits?
> - Why isn't there an officially-released 64-bit image?

This is great information. Feel like writing it up? I'm sure Ian can be
convinced to put it into the right place.

On Oct 16, 2007, at 10:36 , Andrew Gaylard wrote:

> 5. What are the advantages/disadvantages to using 64-bits?
> - The first advantage is that your image size can be enormous.
> If you need the size of your VM code + in-memory image to exceed
> 4 GB, then 64-bits is for you.  Note that it will take ages to
> write out
> an image that's this big to disk.  The sort of applications that need
> this are those which load a small(ish) image, and run code that
> creates millions of objects, but don't save them back to disk in the
> image.

However, the garbage collector really is not up to the task of
collecting multiple gigabytes of garbage.

> - Another advantage is that when the 64-bit-VM is built, the C
> compiler
> knows the ABI is different from the 32-bit ABI.  The x86-64 case is
> an important example: the old i386 ABI offered few registers, used
> i387 floating-point,  and passed parameters on the stack.  The x86-64
> ABI has may more registers, has SSE, SSE2, etc for FP, and
> passes parameters in registers where possible.  It also has additional
> instructions (MMX et al).  All of this makes for a VM that runs faster
> if the compiler is able to make use of it (and is told to at
> compile-time).

I doubt that, you need to profile. I have not heard anyone reporting
the 64 bit VM to be faster than the 32 bit version, on any machine.

> 6. Why isn't there an officially-released 64-bit image?
> Watch this space!

Because nobody needs it (yet), and therefore nobody feels an urge to
provide and maintain one.

Anyway, writing this up for future reference is needed, thanks for
doing this. One thing you should watch out for though is to
distinguish between a 64 bit VM and a 64 bit image, which are
independent.

- What is a 64 bit VM?
A 64 bit image is an image in which the object memory uses 64 bit word
size for object pointers. Squeak now supports a 64 bit image format that
is sufficient to produce a working system, but which is intentionally
simple, and is expected to be modified and extended to take advantage of
additional 64 bit capabilities in the future.

- Can I run a 32 bit image on my 64 bit computer?
Yes. A 32 bit image can be run on either a 32 bit VM or a 64 bit VM. Some
computer platforms (e.g. 64 bit Linux) can run both the 32 bit VM and
64 bit VM on the same system.

- Can I run a 64 bit image on my 32 bit computer?
Yes. If you build a VM with the "64 bit VM?" check box selected, you will
create a VM that runs 64 bit images. This will work on 32 bit host systems
as well as on 64 bit host systems.