Squeak on Palm III (Repeat of my earlier response)

Donald T. Major, II sasdtm at unx.sas.com
Thu Sep 24 14:33:38 UTC 1998

wirth at almaden.ibm.com wrote:

> Markus Kohler said:
> >As far as I know the Pilot processort is not 32 Bit.
> >Therefore porting Squeak could be difficult.


> The issue of porting Squeak to Palm OS keeps coming up, so I'll repeat my
> earlier msg below.  The current update is that there is an undocumented
> system call in Palm OS that can be used to get around the memory write
> protection (MemSemaphoreReserve(), see "really bad news" below), but the
> issues of having to break up the Squeak heap into 32KB "pages" still
> remain.


Actually, there's no design limitation in the 68k series at all concerning this:
the chip has plenty of addressing modes which treat memory as one great big
linear address space (albeit limited to 24 meg). The mac (and apparently the
Palm), simply made heavy used of a particular "near" addressing mode which
incorporated a signed 16-bit quantity into the instruction, to be applied to a
base register value. There are plenty of other addressing modes which aren't so

The only problems I can see concerning memory is that you'd want to allocate
several contiguous blocks for your heap, which
the Squeak VM would memory manage for itself using the less restrictive
instructions (which may or may not be possible, and certainly may require a some
tinkering with the compiler to make sure it uses "far" references as much as
possible), and that you'd want to make sure that any PalmOS register/data
structure reference conventions that the OS saw were resolved back into the
"near" reference format.

 ..  Donald Major           System Developer    677-8000, x6937
dtm  sasdtm @ unx sas com   SAS Institute Inc   http://www.unx.sas.com/~sasdtm/
"Remember those stats that compare the life spans of men vs. women, married vs.
 unmarried men, etc.? Has anyone analyzed Mac vs. Wintel users?"-Stephen Yanusz

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