Re: MCL 2.0.1

[reti@cambridge.apple.com (Kalman Reti)]

At  5:54 PM 12/28/93 -0600, Sheldon S. Ball wrote:
>In the *README* file in MCL 2.0 -> 2.0.1, it says
>
>"The file "ptable" that was copied to your "ccl:" folder is a new ptable init.
>If you use the ephemeral garbage collector, have an MMU on your Mac, and
>are not using virtual memory, drag "ptable" to your system folder."
>
>How do I know if I am using the ephemeral garbage collector?

This is all documented in the reference manual.  You won't be using EGC unless
you turn it on with (egc t).  Using EGC results in shorter GC outages (pauses)
at the expense of using a greater total amount of CPU time to collect the same
amount of garbage.

>How do I know if I have MMU? (IIfx or Quadra 950?)

All machines using 68030's (e.g. your IIfx) or 68040's (e.g. your Quadra) have MMU
built into the chip.  It was an optional extra part on 68020 machines and not available
at all for 680000 machines.

>I do not use virtual memory.
>
>So far it seems to work without ptable in the System Folder?

The ptable init sets up the hardware so that EGC is more efficient.  It does this by
setting up the address space of your machine to have 4K pages.  However, this makes
the average memory reference take a bit longer (because by being on a different page
it might not be in the cache).

So the only reason to use it is if you want to use EGC and want the EGC to run as efficiently
(e.g. quickly) as possible.  This is usually the case for an interactive application where the
pauses due to GC need to be as unobtrusive as possible.

>
>My apologies for these dumb questions!

No problem, better to ask than not use MCL!!  ;->

>
>Thanks, Sheldon


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