[Openmcl-devel] OpenMCL Versions

[Gary Byers]

On Tue, 15 Aug 2006, Hamilton Link wrote:

> Raffael Cavallaro wrote:
>
>> It seems like supporting 32 bit intel is  unavoidable unless you never 
>> distribute your software to other mac  users.
>> 
>> Raffael Cavallaro, Ph.D.
>> 
>
> Supporting 32-bit intel is easily avoided by not porting to it ;).
>
> But seriously, the need to deploy their software on OSXintel32 seems like it 
> would be a compelling argument, if there was anyone who needed to do this.  I 
> was just responding to Andrew's question about platform support based on my 
> impression.  If anyone wishes to distribute openmcl-derived software on 
> intel32 they might want to make sure Gary knows, because at the moment I 
> don't think he's planning to support intel32,
>
> but it's easy enough for him to clear that up...  Gary, is that still the 
> case?
>

I think that it'd be better for the short-term future of OpenMCL if there
were a 32-bit Intel port.  (It would have been better for the recent past
if such a port had existed in January.)

We had a customer willing to fund a 64-bit x86 port.  That particular
user was already running into address space limitations on 32 bit
platforms and didn't see that a 32-bit Intel port as being a wise
investment.  I tend to agree with that: if you had to pick one or the
other, I think that it'd be hard to justify investing time and money
on an x86-32 port.

In a perfect world, you wouldn't have to pick one or the other.  It's
not a perfect world.  I would certainly rather not have to say that
OpenMCL doesn't support most current Apple hardware; unless and until
time and/or money appear for a 32-bit Intel port appear, I have to
say that.

The good news is that (if rumor sites can be trusted and if the port
to x86-64/Darwin goes reasonably smoothly) that won't be true
indefinitely and may not be true for very long.  If a 32-bit Intel
port was started now and was done at end of the year, how much (then)
current Apple hardware would it support that the 64-bit port doesn't ?

One of the things to bear in mind is that (unlike the PPC and Sparc
and (AFAIK) MIPS architectures), x86 progams generally benefit from
being compiled in 64-bit mode: 64-bit programs generally burn memory
and cache lines faster, but (unlike their counterparts on saner
architectures) 64-bit x86 programs have twice as many registers
available to them.  C compilers like that at least as much as Lisp
runtime systems do, and the Intel world has additional motivation
for switching to 64 bits beyond the (still fairly esoteric) need
to overcome address space limitations.

I'm not sure how long it'll take for 32-bit Intel systems to turn into
G3s (and however long it takes there will certainly still be many
millions of them out there).






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