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#1 2017-06-05 13:40:21

From: Spain
Registered: 2014-11-15
Posts: 1

Mac OS 9.2.2 Memory Limit of 1.5 GB...Broken!

We should inform the other forums about this !  This is pretty crazy... 15 years after the OS 9 funeral it is getting a genetic overhaul,
128MB might not seem like much until you consider that 128MB is what many users had in the Classic Mac OS era to run OS 9 and all their applications.

In the big scheme of things, this is quite remarkable smile

Done. … n.2048385/


#2 2017-06-05 14:51:14

MacOS Plus
Registered: 2015-12-09
Posts: 110

Re: Mac OS 9.2.2 Memory Limit of 1.5 GB...Broken!

Just for clarity I'll note that this benefit applies primarily to the PowerMac G4 Mirrored Drive Door Firewire 400, as this is the only model right now with full support for booting OS 9 and the 'official' physical capability to accept more than 1.5GB of RAM.  I've read that 'Unofficial' support for 2GB of RAM is supposed to be possible on the G4 Sawtooth and Gigabit Ethernet models also.  I will attempt to verify that on one of my Sawtooths.  If anyone here can test those models, please post results.

  The earlier work to extend OS 9 boot support to other models has been incorporated into the replacement Mac OS ROM file which allows the access to the increased RAM.  I have personally tested this on the 'unsupported' machines I've already been successfully running OS 9 on with nearly complete hardware support - MDD FW800 and Xserve Rev.1.  At the moment I believe the next best candidate for functionality is one version of the eMac.  Work continues on extending/patching driver issues in order to expand the line-up.

<update>  After much fighting with my Sawtooth I managed to get the system to recognize 1.75GB of RAM with the DIMMs I had available.  The free RAM with the altered Mac OS ROM is reported the same as the other systems tested so far - about 1.57GB.  A physical 2GB of RAM should be possible to install given DIMMs the Sawtooth motherboard won't reject, but for the purposes of the test 1.75GB was sufficient to prove the current 128MB gain works.

Last edited by MacOS Plus (2017-06-05 16:28:38)


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ThinkClassic specialises in the use, maintenance, repair, restoration and modification of vintage computers and peripherals.