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You are here: MacNN Forums > Hardware - Troubleshooting and Discussion > Mac Notebooks > Turning L2 Cache on and off?

Turning L2 Cache on and off?
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hldan
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Oct 30, 2003, 01:14 PM
 
I read in a different forum that when people are installing CHUD the 4th CD with Panther it will show that L2 cache is not activated.
Then they mention about turning it on but not how they were doing it.
I have the 17"PB 1.33Ghz with 512K L2 Cache. I would like to know how (if really possible) to turn the L2 cache on or off?
I want to make sure mine is on for optimal performance.
Any help thanks.
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docholiday
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Oct 30, 2003, 02:18 PM
 
Yea, after reading the article about Panther possibly deactivating L2 cache over at MacBidouille, I am eager to find out how I can check...

I have XCode installed, don't know where to go from there...
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superlarry
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Oct 30, 2003, 02:23 PM
 
when you're installing the developer tools, customize the install and add the CHUD tools. You'll get an extra system preference pane called "Hardware" which will tell you if your L2 cache is on and give you the option to turn it on/off.

mine was already turned on with my powerbook 12" rev A.
     
pysan
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Oct 30, 2003, 03:01 PM
 
If you just check out the system prefs as someone already said, there should be a hardware preference pane at the bottom that gives you the L2 cache option. I have the menu bar status showing on my iBook as well, so it is fairly easy.
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machem
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Oct 30, 2003, 07:00 PM
 
One thing I noticed is that everytime I opened up the "Hardware" pane, the L2 cache was always "off".

I don't know if it was actually off, but I'll run XBench to find out.
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ibook_steve
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Oct 31, 2003, 12:12 AM
 
If Apple shipped their machines with L2 turned off, believe me, you'd know it. Going between L1 (on chip registers) and orders of magnitude slower memory would probably kill performance.

Steve
     
machem
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Oct 31, 2003, 12:30 AM
 
Originally posted by ibook_steve:
If Apple shipped their machines with L2 turned off, believe me, you'd know it. Going between L1 (on chip registers) and orders of magnitude slower memory would probably kill performance.

Steve
Yeah, I understand that. What I was worried about was perhaps with CHUD installed, it was always off somehow. In other words, if I go into CHUD and turn the cache "on", the next time I use that pane, the drop-down should say "on", not "off".

I tested it with XBench, and despite what the pane implies, turning it on keeps it on.
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bigben1024
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Oct 31, 2003, 01:05 AM
 
for what reasons would one elect to dissable their L2?
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markmentovai
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Oct 31, 2003, 01:12 AM
 
CHUD 3.0.0, as supplied on the Xcode CD in the Panther package, doesn't know what to do with the Motorola 7447/7457 CPU. You'll notice that it's got some less-than-production-quality text like "(null)" in the Hardware preference pane if you're using 3.0.0 on a new Aluminum PowerBook.

Since it can't make sense of the CPU, it gives erroneous information for the L2 cache and doesn't let the user control it.

Upgrade to CHUD 3.0.1. Either use the CHUD Updater at /Developer/Applications/Performance Tools/CHUD/CHUD Updater.app if you already have CHUD installed, or download a fresh copy from ftp://ftp.apple.com/developer/Tool_C...ormance_tools/ .

The CHUD 3.0.1 release notes say:

"-_Added support for PPC 7457 processor (Aluminum PowerBooks)"

With CHUD 3.0.1 installed, the Hardware preference pane will accurately identify your CPU, will tell you that your L2 cache is active (unless you've disabled it), and allow you the option of turning it off.

Mark
     
machem
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Oct 31, 2003, 01:31 AM
 
Thanks, Mark!
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11011001
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Oct 31, 2003, 01:31 AM
 
What does the Nap option do?
     
blythe
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Nov 8, 2003, 11:43 AM
 
Originally posted by markmentovai:

With CHUD 3.0.1 installed, the Hardware preference pane will accurately identify your CPU, will tell you that your L2 cache is active (unless you've disabled it), and allow you the option of turning it off.

Mark [/B]
Thanks, Mark, for this information. I was beginning to get paranoid that my new 17" was not performing to it's potential. I too, am curious as to what the Nap option does. My new 17" with it's PowerPC 7457 v1.1 has the Nap option turned on by default. My dual 1.25 with it's PowerPC 7455 v3.2 has it off by default. What exactly does the Nap option do? Does it enable the processor to use reduced power settings? Should I keep it on, even when I use the "Highest" performance settings with my AC power plugged in?
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