Re: IIgs

[dempson@atlantis.actrix.gen.nz (David Empson)]

In article <441bcb$5iv@styx.uwa.edu.au>,
Joseph Turner <jturner@tartarus.uwa.edu.au> wrote:
>   Hi, I have just got myself a IIgs and I am pretty excited but at the 
> moment have a few questions.
>  The System I am using is an old one ....system 4. And the IIgs I am 
> using is a ROM 1 512k IIgs. 

I'll second what Clay said: you need at least 1 MB to be able to use
current versions of the IIgs system software, and most current
applications.  I would recommend at least 2 MB to allow you to run
most software, or better still 4 MB, which gives you enough to do
anything.

Get a larger memory expansion card!

>   Firstly, when I get into the chooser I cannot seem to make a ram disk 
> because when I continue and try and load the system, the system says I do 
> not have enough memory to make the ramdrive, although it lets me get to 
> that point.

System 4.0 requires 512K to run, so you cannot set up a reasonable RAM
disk, as there will not be enough memory left to load the operating
system.

Note that there are two settings for the RAM disk size on the ROM 1
IIgs: the "Minimum" and "Maximum" size.  These should always be set to
the same value, to ensure you don't get compatibility problems or
strange errors.  The ROM 3 only offers a single setting for the RAM
disk size.

The two different sizes seemed like a good idea when the IIgs came out
in 1986, but it turned out to have too many problems.  The worst one is
that if the RAM disk needs to grow after startup time, the additional
memory may be allocated some distance from the existing area, leaving
a "hole" in the memory that cannot be merged with adjacent free areas.
(This is called "memory fragmentation".)  The net result is that you
might have less memory available than you should, because it is not
all in one area.

To avoid this sort of problem, always set the minimum and maximum size
to the same value.

Note: if you change the RAM disk size, you have to force a cold start
to have the change take effect (except when first creating the RAM
disk).  To do this, start a self-test (Ctrl-Apple-Option-Reset) then
reboot (Ctrl-Apple-Reset).

> One thing I have noticed is that ticks appear next to the left column
> when I put in 0k. 

Read the section on the control panel in the user manual.  The tick
indicates that the selected value is the default.

>   Also another query I have is to do with the disk cache. When I set the 
> cache to 256k

... you will have no memory left, as the operating system uses 512k.
It will not actually be able to use 256K for the cache (it might be
able to use about 32K).  This setting specifies the maximum size of
the cache, and the memory will be released for other uses if necessary.

> one would expect the disk swapping to be very minimal but I sware I
> have done about 15 disk swaps and the end of copying is nowhere  
> in sight. The file that I am coping is onlt about 20k!

The GS/OS disk cache is not used for caching all data: it usually only
caches directory information, and then only for drives for which the
drivers make use of the cache (a 5.25" drive is never cached, and
neither is the RAMFast SCSI card, but it has its own on-card data
cache).  There isn't much point caching data as it just wastes memory
that could be used for something else.  Programs can specify whether
to cache data on each read or write call, but this isn't used much.

The basic problem is that you don't have enough memory.  If you go
into the text mode Control Panel while you've in Finder, and look at
the "Total Free RAM" indication on the RAM Disk screen, you will
probably find that you have very little memory left, which is why
Finder is having to do so many disk swaps.

If you get rid of the RAM disk, you will probably find that you have
enough memory to do a small file copy in a reasonable number of
passes.  (The RAM disk always uses at least 32K if it is enabled.)

You should also set the cache back to 32K, but it probably won't be
used anyway.
-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand