[Openmcl-devel] 64-bit

Daniel McShan dan at syzygyx.com
Fri Dec 5 11:24:04 PST 2003

Well believe it or not, that is a far better answer than I've gotten 
from Franz or Xanalys.  Okay so it's not THAT hard to believe.


On Dec 5, 2003, at 12:13 PM, Gary Byers wrote:

> On Fri, 5 Dec 2003, Daniel McShan wrote:
>> Hi.
>> What kind of support does OpenMCL have for the 64bit architecture of
>> the G5?  For instance, could I conceivable have a lisp image with 8GB
>> of memory?  I'm interested in both linux and darwin, though I
>> understand that the current implementations may not exactly support
>> 64bit memory...
>> Thanks,
>> Dan
> OSX doesn't (yet) (fully) support the execution of 64-bit programs;
> you can sort of get the processor to run in 64-bit mode, but you're
> limited to a 32-bit address space (and aside from a little bit of
> C compiler support for arithmetic on "long long" integers, foreign
> code still passes 32-bit values around.)  It's reasonable to assume
> that these limitations will be removed in the future (though I don't
> lnow whether Apple's formally announced that), and it -is- possible
> to get a mostly-64-bit lisp running in this environment (running in
> a 32-bit address space and doing 32-bit foreign function calls.)
> Even if that weird hybrid environment's kind of short-lived, a lot
> of the work that needs to be done to get OpenMCL running in a "true"
> 64-bit environment could be done now.
> Things are a little further along on the Linux side: it's possible
> to build a 64-bit kernel, development toolchain, and libraries (see
> <http://www.penguinppc64.org>.)  I actually have a sort of hand-rolled
> 64-bit LinuxPPC environment running on an old Power3 system and
> commercial Linux distributions are available for 64-bit IBM servers
> and workstations.  The G5's a bit different from those systems 
> (different
> bus, different peripherals), and Linux distributions for the G5 are
> on the near horizon but aren't quite available yet.
> Getting a 64-bit OpenMCL running on either platform's a fair amount
> of work, and I've been doing some of that work for a while now.  Let's
> say that I'm not very confident that it'll happen by the end of 2003,
> I'm very confident that it'll happen before the end of 2004, and would
> have to do a bit more work than I have to be comfortable predicting
> how early in 2004 it'll be ready.  Is that answer evasive enough ?
> In 64-bit LinuxPPC, the address space available to a process is limited
> to something around 42 or 43 bits; I'm not sure how much of this is a
> software limitation and have no idea what the situation will eventually
> be like on OSX.  I imagine that a lot of people would settle for a
> 1000X increase in available address space (at least until they started
> GCing ...), at least for the time being.
> Gary Byers
> gb at clozure.com

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