Michael Sokolov <[EMAIL PROTECTED]> wrote:
> Why does PalmOS have the notion of memory "cards"? AFAIK because the
Dragonball does.
Um, no, I don't think so...
The Pilot, PalmPilot, and Palm III all had RAM and ROM on a removable card. The
concept of memory cards was an architectural thing to allow us to eventually
support more than 1 of these removable cards. It is currently used a little bit
in the Macintosh simulator, and really taken advantage of in the HandSpring
Visor.
Michael Sokolov <[EMAIL PROTECTED]> wrote:
> Why is everything in PalmOS (chunks, records, resources, you name it) designed
around
> the 64 KB limit? Probably because of the -32 KB to +32 KB locality of
reference limit in the 68000.
Actually, no. Most of this stuff _isn't_ designed around 64k. The initial
implementation was limited to 64k because the natural word size of the processor
was a 16 bits, and every byte counts on a 128k device. So, many (private) size
fields & whatnot were 16 bit integers. 64k was actually the maximum size of a
memory heap, and we had multiple heaps. Most of that was fixed long ago,
however. The only remaining 64k limit that I'm aware of is for HotSync. All
chunks (dynamic memory, resources, records, etc...) in RAM or ROM on the device
can be bigger than 64k... the high level allocation routines still artificially
limit some allocations to 64k because we do not want a chunk >64k to be attached
to a database. Once its part of a database, then hotsync might try to transfer
it, and Bad things would happen. Engineering has been pushing to get this last
piece fixed for a while now. When that happens, then all of the allocation
routines will allow >64k requests. Note that the size parameters in these
routines have always been 32 bits long.
Hope you found the history bits interesting...
Jesse
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