Classic Mac OS Software (Discussions on Applications) > Hacking the System, Mac OS 9.3, and Beyond !

Mac OS 9.2.2 Maximum RAM and Real world observations

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DieHard:
In the past... it was noted that certain applications get buggy when system has more than 1 gigabyte of physical RAM under OS 9.

Also, Web and print references will vary... some will state that Mac OS 9 can address to 2 GB of RAM, while others say the 1.5 GB limit is the maximum. 

I decided to create this thread to gather user experiences with Mac OS 9 applications and RAM limits; also to wipe the slate clean and try some real world testing and the explore Mac OS 9 system limits.

So let's begin...


--- Quote ---We will use an Powermac G4 MDD as the test unit since it has 4 slots and we will start with 3 out of 4 filled (512MB X 3) for a total of 1.5GB

--- End quote ---


No Shocker here... Built-in Memory (or Physical Memory) is 1.5 GB and finder shows Memory used per application and the System itself using 68.1MB, Also the largest unused Block (of available memory) is 1.41GB

Now for test 1: We create the maximum RAM disk allowed (and tell it to re-create on Boot up) of 256 MB and re-start



Hmmm... pretty interesting, but expected... Built-in Memory (or Physical Memory) is 1.5 GB and finder shows Memory used per application and the System itself using 314.8MB instead of 68.1MB (this is obviously the overhead of the RAM disk itself and shows an increase of 246.7MB (not 256MB), But now the largest unused Block (of available memory) decreases down to 1.17 GB (a .24 GB Difference.... off by .1 since a 256 MB RAM Disk should be .25 GB)
We can conclude that although the numbers are not 100%, the small deviation is acceptable and that a RAM disk will decrease the available memory and proportionately add itself into the Mac OS category as far as Memory used.


--- Quote ---OK so let's go for broke... now we have 4 out of 4 filled (512MB X 4) for a total of 2 GB, we expect from all printed material that the system cannot go past 1.5 GB
--- End quote ---


OMG the system sees it ! (or does it)... Built-in Memory (or Physical Memory) is 1.99 GB !!

Finder shows Memory used per application and the System itself using 564.9 MB (What the F%$k), Also the largest unused Block (of available memory) is 1.42 GB.... wait a minute we add 512MB and we only get .01 GB more in available memory (from 1.41 to 1.42) and the OS itself is now bloated from 68.1MB to 564.9 MB (496.8 MB increase) ??!!

We can theorize that the ceiling is actually 1.5 GB (or maybe 1.6 GB since we now have 1.42 GB unused) and we can assume that it does not know what to do with the extra 512MB so it adds it to the Mac OS category as used by the system itself and it like a dead fish or more like a wasted layer of resources that we cannot get to :(


--- Quote ---Wait... Maybe we can use it as a RAM Disk ? at least grab back 256 MB...
--- End quote ---

Now for test 2: We create the maximum RAM disk allowed (and tell it to re-create on Boot up) of 256 MB and re-start



Hmmm... this sucks, just as bad as before... yet kinda interesting... Built-in Memory (or Physical Memory) is 1.99 GB and finder shows Memory used per application and the System itself using 811.9 MB instead of 68.1MB !!! (this is obviously the overhead of the RAM disk and the wasted 512MB); Mactron would have a nervous breakdown if he saw his System use 811.9 MB (he gets upset if he wastes 1 MB), Now the largest unused Block (of available memory) decreases down to 1.18 GB (the worst number yet).

Again, we can conclude that although the numbers are not 100%, a RAM disk will decrease the available memory and proportionately add itself into the Mac OS category as far as Memory used. Also, the idea of trying to load the RAM disk into the unused area between (1.5 GB to 2 GB) and reclaiming some of the wasted RAM above 1.5 GB was a bust. Until,  the Mac OS 9.4 Update is released (that may take a while), we are stuck with a 1.5GB physical memory limit in OS 9.2.2 as far as the OS is concerned.

NEXT... Please post your experiences of application limits/issues here...



Protools5LEGuy:

--- Quote from: DieHard on December 09, 2014, 10:26:36 PM ---
We will use an Powermac G4 MDD as the test unit since it has 4 slots and we will start with 3 out of 4 filled (512MB X 3) for a total of 1.5GB


--- End quote ---
You are pro Mono vs Duals. I have a MDD Dual 866 with 2 gigs installed of Kingstom DDR-400, Asus Gforce 2MX Twin (Only VGA output) with an Audiomedia III.

I will try to mimic your install and make your tests on my machine if that could help anyway. It could also compare CPU, Dual vs Mono and bandwith as my bus will run 133 and my mem 266.

IIO:
Wait... Maybe we can use it as a RAM Disk ?

lol^^

DieHard:

--- Quote from: IIO on December 10, 2014, 12:17:23 AM ---Wait... Maybe we can use it as a RAM Disk ?

lol^^

--- End quote ---

Guess you been there :)

MacTron:
The Mac Os 9 can address up to 4GB of memory. But due to memory map structure, up to 1.5 GB can be RAM, the remaining can be ROM or what ever. This 1.5 GB limit could be enough at its time ... but now a days...
If More than 1.5 GB of RAM is present in the machine, only 1.5 is usable as RAM, the remaining appears as used by the Mac Os, who knows in which way ... LOL

So we only have to change the memory map where it puts 1.5 we shall put 2 o 3 GB... LOL

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