Powerbooks... why no L3 cache?

Demon Hunter

macrumors 68020
Original poster
Mar 30, 2004
2,284
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So I was playing with my friend's TiBook the other day, and noticed he has 1MB of L3 cache.

I'm curious... I know that L2 cache is faster than L3 cache, and that the L2 currently stands at 512k... but why does the current design not include L3 like the TiBooks of yore? Anyone know?
 

Mord

macrumors G4
Aug 24, 2003
10,090
21
UK
motorola stoped developing the 7457 the last ship to support L3 cache, that chip only went to 1.3GHz.
 
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Chaszmyr

macrumors 601
Aug 9, 2002
4,264
76
L3 caches aren't really so great, it's too bad the PowerBooks don't have a 1mb L2 though.
 
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Mord

macrumors G4
Aug 24, 2003
10,090
21
UK
the g4 tends to get a quite decent kick out of L3 cache it compensates for the slow ass MPX bus 2MB L3 can add 10-25% performence
 
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w00tmaster

macrumors regular
Jun 21, 2004
165
0
Chaszmyr said:
L3 caches aren't really so great, it's too bad the PowerBooks don't have a 1mb L2 though.
Heh, actually even the g5 powermacs only have 512k l2 cache, until recently it has pretty much been the standard, though some of intel's newest offerings have 2mb l2 cache(though still nowhere near what the sun workstations at school have, 8mb :p )
 
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Mord

macrumors G4
Aug 24, 2003
10,090
21
UK
the g5 dose not need L3 cache as the bus is so hyper fast the ram acts like a giant.

same go's for AMD.
 
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auxplage

macrumors 6502
Nov 11, 2004
331
1
Virginia Beach
Hector said:
motorola stoped developing the 7457 the last ship to support L3 cache, that chip only went to 1.3GHz.
What chip was the put in the 1.42 ghz G4 PowerMacs produced because they had 2MB L3 cache and 256KB L2? Was it the 1.3 ghz chip you speak of simply overclocked by Apple?
 
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Bear

macrumors G3
Jul 23, 2002
8,089
4
Sol III - Terra
auxplage said:
What chip was the put in the 1.42 ghz G4 PowerMacs produced because they had 2MB L3 cache and 256KB L2? Was it the 1.3 ghz chip you speak of simply overclocked by Apple?
The processors in the MDD dual 1.42GHz are not overclocked. They were rated for 1.42GHz by Motorola. It's just tha they never made more than enough for Apple to ship in the MDD PowerMacs.
 
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Bear

macrumors G3
Jul 23, 2002
8,089
4
Sol III - Terra
dferrara said:
So I was playing with my friend's TiBook the other day, and noticed he has 1MB of L3 cache.

I'm curious... I know that L2 cache is faster than L3 cache, and that the L2 currently stands at 512k... but why does the current design not include L3 like the TiBooks of yore? Anyone know?
Having the 512M L2 cache compensates for around 2MB of L3 cache with a 256M L2 cache.
 
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Sun Baked

macrumors G5
May 19, 2002
14,874
57
Motorola hasn't updated the L3 cache bus in a long time, thus the L3 cache would be operating at about the same speed they were with the last PowerMac G4s.

The L2 cache is on the CPU and operating much faster, thus it was a better and less expensive option at the time. Apple dumped it at the right time, when the 7447 was faster than the 3rd generation 7455 with L3 cache.

Anyway L3 caches are falling to better options like integrated memory controllers and larger on-chip caches.
 
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AstroManLuca

macrumors member
Mar 18, 2005
86
0
Minnesota
And the reason that L3 cache was dropped from the 7447 in the first place is because when overclocking, the L3 cache is the first thing to fail. I had a 1.25-1.33 GHz G4 upgrade with 2 MB of L3 about a year ago, and if I disabled the L3 I was able to get it stable at 1.467 GHz. With the L3 enabled, even 1.40 GHz was slightly unstable.

It's cheaper to ditch the L3 and let the clock speed rise to 1.5-1.87 GHz without problems. A friend of mine has a dual 7447 upgrade in his PowerMac running at 1.87 GHz.
 
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Mord

macrumors G4
Aug 24, 2003
10,090
21
UK
there is allot of misinformation here so i'll set everything straight, if you disagree do the research and you will find i am right.

the MDD G4 used a 1400MHz (some say overclocked 20MHz but seriously who cares) 7455 G4 chip from motorola it's written on the die in gold ink.
Motorola from the introduction of the G4+ made two versions of the G4+ one with the extra pins for L3 cache another without the 7450 and the 7440, this carried on to be the same with the 7455 and the 7445 and again with the 7447 and the 7457, they are other than the extra pins exactly the same and pin compatible the 745x chips can be used without L3 cache as they were in some emacs, the last apple computer to support L3 cache was the mdd g4, now after that apple either used 7455's with no L3 cache or 7445's and latter on 7447's 7447A's and in the mac mini and current powerbooks the 7447B, apple has never and will never used the 7457, only a few upgrade manufactures did and they alone are not push enough for motorola to develop the chip so motorola dropped the 745x chips and now only develops the 744x chips in use by apple today.

oh and dude above use the powerlogix cache ratio utility to push the cache ratio up so the cache stays at the same speed but the cpu speed can increase, it's on a multiple much like the cpu is on the fsb.
 
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Demon Hunter

macrumors 68020
Original poster
Mar 30, 2004
2,284
39
So are you saying the current Powerbooks are using 7447B? I thought it was still 7447A.
 
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maya

macrumors 68040
Oct 7, 2004
3,225
0
somewhere between here and there.
Chaszmyr said:
L3 caches aren't really so great, it's too bad the PowerBooks don't have a 1mb L2 though.
I agree a 1MB L2 cache would have helped the G4 and PowerBook line quite a bit.

I was about to order a PB for some extra mobile screen real-estate since I will be in one location for a few months and said why not, then I compared all the NEW offerings and it was not compelling at all. An outdate Video card, slow PCI 8x, and the rest just was depressing for that kind of money. Decided to hold off till Tiger was released or some other better updated hardware.

Hope Apple implements PCI-e into the lineup since it targets the pre-press, video, audio, etc....industry. :)
 
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