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Increase cache speed for certain G4 upgrade cards System
New PowerLogix and Sonnet upgrades are available for G4 systems. These upgrades have 1 to 2 MB of L3 cache on them. PowerLogix chips require a special piece of software for the L3 cache to be recognized in OS X (called Cache Control X). Here is a way to overclock your cache using the Terminal:
  1. Install the software provided by PowerLogix

  2. Type in sudo plxcache -off in the Terminal

  3. Type in sudo plxcache -r 3.5 where 3.5 is the ratio controlling the cache speed in regard to the bus speed (3.5 gives you 229 MHz cache in a 100 MHz system bus, etc)

  4. Experiment until you can achieve the highest speed with stability
Check the GUI software that they give you to determine the speed. If you set the speed too high, you will have to restart your machine. There is no damage done at all and it can run very safely at a higher speed. If you want to set the speed to change when your computer boots, make an AppleScript as follows:
 do shell script "plxcache -off" password 
"ADMIN PASSWORD" with administrator privileges
do shell script "plxcache -r 3.5" password
"ADMIN PASSWORD" with administrator privileges
Save it as run-only and put it into your login items. This works for Sonnet and PowerLogix chips alike.

[Editor's note: I don't have a G4 upgrade card to test this with ... insert standard "backup before experimenting" advice here!]
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Authored by: psandiford on Nov 20, '02 12:51:43PM

I have the PowerLogix Cache Control for my Pismo. After installing it my system would lock-up no matter what the cache was set at. I do not recommend its installation.

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Authored by: jimw on Nov 20, '02 04:04:48PM

I have a Sonnet Encore/ST G4 1Gig card. the command pixcache was not recognized, i.e.:

sudo plxcache -off
sudo: plxcache: command not found

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Authored by: jbouklas on Dec 11, '02 03:39:50PM

Did you install the appropriate software (it installs the command line software that way)? Do a search on PowerLogix's site for their software.


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Authored by: Thray on Nov 21, '02 08:59:34AM
Sonnet doesn't require the installation of Cache Control software to my knowledge, and that's where the command comes from. I'm not sure the software will even work with Sonnet hardware although it's entirely possible. You can find it at under Support -> Downloads -> Cache Control (you're looking for 2.1b4). I do not know what kind of risks are involved trying to use Powerlogix software on Sonnet cards. You may want to check out xlr8yourmac forums for info about that beforehand.

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Authored by: Thray on Nov 21, '02 09:19:50AM

I gave this hint a shot on my Powerlogix 1GHz Cube upgrade, and it does work. However not just any ratio will work. So far only 3.5 has functioned for me. 2.5 was valid but crashed my system (it is fine). I have found nothing else valid, even 4 which should be the default ratio. BTW, this is ratio vs. the CPU speed I think, not system bus, i.e. 1000MHz/3.5 = 286MHz cache (as listed in software after mod is done), 1000/4 = 250MHz (default), 1000/2.5 = 400MHz (I wish).

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It should work fine on Sonnet Cards
Authored by: jbouklas on Nov 21, '02 05:10:27PM

I originally heard of this from a guy who has a Sonnet card. I tried it with my PowerLogix card and it works beautifully (3.5 is the best I can do without it crashing). I'd like to see what happens if an owner of a stock Apple G4 CPU with L3 cache used this program. I think it would work for them as well.


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Increase cache speed for certain G4 upgrade cards
Authored by: sucram3 on Nov 21, '02 05:14:09PM

This is old news actually. The Powerlogix software Cache Control X 2.1b4 does work with the Sonnet Crescendo G4 800 daughter card upgrades. I used it to enable the L3 cache on the card in my Power Tower Pro. I played around with different cache speeds but I stopped using it in favor of the SonnetCache.kext extension because it later became apparent that the it was not enabling the onboard L2 cache. There is a work-around for this by using Ryan Rempel's L2CacheConfig to enable the L2 along with Cache Control X. I have not tried this combination yet but it is reportedly stable.

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