Re: IIGS Ram Doubler?

[GUDATH@EZINFO.VMSMAIL.ETHZ.CH (GUDAT,HENRIK MICHAEL)]

In <1995Jul11.234105.1354@news.etc.bc.ca> rprest@cln.etc.bc.ca writes:

> 
> 	I've recently read about a program called a Ram Doubler for the 
> Mac.  It's supposed to use some sort of virtual memory arrangement to 
> double your memory.  Is there such a thing for the IIGS, or could 
> something like that be made? 

Nope, simply because the IIGS doesn't need such a thingy. RamDoubler exists
because the Mac allocates memory blocks of a fixed size (customizable) to each
application. Except for reserving memory ioutside the application heap
(introduced with System 7 and called "temporary memory"), there is no way for
an aplication to increase its heap.
Because applications often do not use all of their memory, this scheme wastes
LOTS of unused memory. If you could somehow paste the unused bytes of the
various applications in memory together, you could possibly launch another app.
But the Mac isn't that flexible.
That's why RamDoubler exists. It steals the unused memory blocks and "recycles"
them. The system thinks they are free.
There is a lot more to RamDoubler (memory compaction and virtual memory) than
just the dynamic reallocation of reserved but free memory, but it gives you a
vague idea.
As for memory compaction and virtual memory, I guess the IIGS is not fast
enough to handle this kind of stuff. And virtual memory only makes sense if the
computer got a MMU. I'm not a techie, so please correct me if I'm wrong...

On the IIGS, memory is always taken from a common memory pool. That's why a
crashing applicvation can easily ruin the rest of the system. On the Mac, the
application usually (take that with a bit of salt..) kills itself only (and a
bit of the system...maybe...:-)) ). On the peecee and system 9 (Gershwin),
memory protection avoids nasty interactions to some degree. But that's another
story..

- henrik