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Does the PB make use of DDR2?
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Grizzled Veteran
Join Date: Feb 2006
Location: Northern VA
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I was wondering today when I read my PowerBook box, it said it uses DDR2 but only runs at 333MHz, so does this mean that the PowerBook makes no use of the 2 in ddr2?
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iMac 24" | Core 2 Extreme 2.8GHz | 4GB RAM | 500GB HD
PowerBook G4 15" HR | 1.67GHz | 2GB RAM | 100GB HD
R.I.P 1995 Toyota Supra NA-T
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Posting Junkie
Join Date: Oct 2005
Location: Houston, TX
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The final revision of the 15" and 17" PowerBooks used DDR2 for cost (DDR2 is cheaper than DDR) and power (DDR2 runs at a lower voltage and produces less heat) reasons rather than performance reasons (333Mhz is already twice the frequency of the G4's FSB).
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Mac Elite
Join Date: Sep 2005
Location: Vancouver, BC
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... That can't be right. The MacBook Pro can't possibly be running DDR2-333. That is *hurt*.
Someone please clarify.
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Posting Junkie
Join Date: Oct 2005
Location: Houston, TX
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Originally Posted by Tomchu
... That can't be right. The MacBook Pro can't possibly be running DDR2-333. That is *hurt*.
Someone please clarify.
PowerBook, not MacBook Pro.
The MacBook Pro has DDR2-667 at 667Mhz.
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Addicted to MacNN
Join Date: Jun 1999
Location: Las Vegas, NV, USA
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They are talking about the Powerbook G4, which require DDR2-333 memory. The MacBook Pro uses DDR2-667 memory.
Chris
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Mac Elite
Join Date: Sep 2005
Location: Vancouver, BC
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Oh, oops.
That's still pretty hurt though. :-( DDR2 at 333 MHz is home to some *extreme* latencies.
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Senior User
Join Date: Apr 2002
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Originally Posted by Tomchu
Oh, oops.
That's still pretty hurt though. :-( DDR2 at 333 MHz is home to some *extreme* latencies.
Yeah, but it's more than fast enough for the G4's slow bus.
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Mac Elite
Join Date: Sep 2005
Location: Vancouver, BC
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That doesn't change the latencies from the memory controller to the memory.
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Posting Junkie
Join Date: Oct 2005
Location: Houston, TX
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Originally Posted by Tomchu
That's still pretty hurt though. :-( DDR2 at 333 MHz is home to some *extreme* latencies.
Latency is usually a fixed time period for a given chip. In the case of DDR2, the common chips (not the "extreme leet high performance wow wow chips with lights and heatsinks") have a latency of about 7.5ns; so if it's 5 cycles at 667Mhz, 4 cycles at 533Mhz, 3 cycles at 400Mhz, or 2.5 cycles at 333Mhz (if DDR2 allows half cycle latency... I forget; DDR allowed it). I'm not sure what the impact of the G4's DDR memory controller is; the G5's DDR memory controller is pretty bad compared to AMD and Intel.
(Last edited by mduell; Apr 25, 2006 at 05:40 PM.
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Mac Elite
Join Date: Sep 2005
Location: Vancouver, BC
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Originally Posted by mduell
Latency is usually a fixed time period for a given chip. In the case of DDR2, the common chips (not the "extreme leet high performance wow wow chips with lights and heatsinks") have a latency of about 7.5ns; so if it's 5 cycles at 667Mhz, 4 cycles at 533Mhz, 3 cycles at 400Mhz, or 2.5 cycles at 333Mhz (if DDR2 allows half cycle latency... I forget; DDR allowed it). I'm not sure what the impact of the G4's DDR memory controller is; the G5's DDR memory controller is pretty bad compared to AMD and Intel.
That's if the Powerbook runs its DDR2-333 at CAS 2.5. You're absolutely correct though.
I've avoided doing any RAM reviews at work lately. I haven't been following up with DDR2 at all.
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