Author Topic: slight RAM issue  (Read 6594 times)

SiMuLaCrUm

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slight RAM issue
« on: 20 December 2008, 04:08 »
I have PC-6400 RAM that is supposed to be 800mhz. I set my mainboard to run it at 800mhz, but when I look at the ram speed using CPUID, it says is running at 400mhz. Any way to fix this?
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davidnix71

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Re: slight RAM issue
« Reply #1 on: 20 December 2008, 05:36 »
Maybe it is running at 800 Mhz. Is it dual channel? You got this as a matched pair, right?

worker201

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Re: slight RAM issue
« Reply #2 on: 20 December 2008, 06:28 »
At least it's only a slight RAM problem...

SiMuLaCrUm

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Re: slight RAM issue
« Reply #3 on: 20 December 2008, 20:42 »
Yes, it is a matched pair running dual channel. The BIOS and the startup tests read it as 800mhz. I'm guessing that the program I used just doesn't read 800mhz, so it reads it as 400mhz.
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Lead Head

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Re: slight RAM issue
« Reply #4 on: 22 December 2008, 02:22 »
DDR is double data rate. Which means the effective frequency is twice the actual speed. In this case the effective frequency is 800Mhz, while the actual clock speed is 400. Programs such as CPU-Z, CPUID often read the actual clock speed. Nothing to worry about at all :)
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SiMuLaCrUm

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Re: slight RAM issue
« Reply #5 on: 22 December 2008, 16:24 »
Yeah, I figured that out when i realized it was dual channel  (Y)
Thanks, it had me and my dad a bit confused when we installed it >.<
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Lead Head

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Re: slight RAM issue
« Reply #6 on: 24 December 2008, 18:35 »
Yeah, I figured that out when i realized it was dual channel  (Y)
Thanks, it had me and my dad a bit confused when we installed it >.<

Dual channel has nothing to do with it. Dual channel just means the sticks of ram are paralleled to double the bandwidth.
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SiMuLaCrUm

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Re: slight RAM issue
« Reply #7 on: 30 December 2008, 16:43 »
Ah, ok. It makes sense now, each of the sticks are 400mhz, but they combine bandwidth.
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Lead Head

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Re: slight RAM issue
« Reply #8 on: 31 December 2008, 21:09 »
Ah, ok. It makes sense now, each of the sticks are 400mhz, but they combine bandwidth.

Nooooo...

MHz means how many clock cycles, in terms of millions of clock cycles per second. So 400Mhz is 400 Mllion On/Off cycles per second. On every clock cycle you have whats called a rising and a falling edge. Rising is during switch on, and falling is during switch off.



Normal non-ddr ram can only transmit dad on the rising edge, but DDR ram can transmit data on both the rising AND falling edges. It effectively doubles the speed. Dual channel means your two ram sticks are in parallel. So each one of your "800 Mhz" sticks is actually running at 400. In dual channel mode you effectively have a single "1600 Mhz" ram stick, or actually for a combine 800Mhz


Think of those push button grill ignitors, or those large push button lighter. Those are like Non-DDR ram, they only spark when you push the button down. If it were a "DDR" lighter, it would spark again when you let go of the button. You are still doing the samething as before, but you able to now get two sparks out of it. In dual channel you would have two grill lighters. Now a "Dual Channel DDR" grill lighter now lets you get  4 sparks per each press and release
« Last Edit: 1 January 2009, 20:14 by Lead Head »
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worker201

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Re: slight RAM issue
« Reply #9 on: 31 December 2008, 22:06 »
Nice metaphor.  Brilliant graphics too :P

SiMuLaCrUm

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Re: slight RAM issue
« Reply #10 on: 5 January 2009, 00:52 »
Ah, ok. It makes sense now, each of the sticks are 400mhz, but they combine bandwidth.

Nooooo...

MHz means how many clock cycles, in terms of millions of clock cycles per second. So 400Mhz is 400 Mllion On/Off cycles per second. On every clock cycle you have whats called a rising and a falling edge. Rising is during switch on, and falling is during switch off.



Normal non-ddr ram can only transmit dad on the rising edge, but DDR ram can transmit data on both the rising AND falling edges. It effectively doubles the speed. Dual channel means your two ram sticks are in parallel. So each one of your "800 Mhz" sticks is actually running at 400. In dual channel mode you effectively have a single "1600 Mhz" ram stick, or actually for a combine 800Mhz


Think of those push button grill ignitors, or those large push button lighter. Those are like Non-DDR ram, they only spark when you push the button down. If it were a "DDR" lighter, it would spark again when you let go of the button. You are still doing the samething as before, but you able to now get two sparks out of it. In dual channel you would have two grill lighters. Now a "Dual Channel DDR" grill lighter now lets you get  4 sparks per each press and release

Ah, it makes sense. And I like the metaphor :)
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