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What is the difference between 64bit and 128bit?

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September 21, 2004 1:51:55 AM

I was looking at both versions for the Radeon 9550 on the Newegg site and they have the same core speeds (250MHz), and effective memory speeds (400MHz). So what is the difference? The reason I ask is on Ebay some people list the card as 64bit but in the description it says 128bit. Can this number refer to something else on the graphics card?

Always remember, you are unique...just like everyone else. :wink:
September 21, 2004 2:29:42 AM

Well think of it as in terms of sand.. Which would be quicker? Moving sand 32 whell barrels at a time, or 128 wheel barrels?
I'm not sure if this applies here, but thats how you would think of it for cpus..

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September 21, 2004 2:52:58 AM

So if I understand correctly, if the person or vendor doesn't specify whether the card is 64bit or 128bit then the only way to tell is to ask? I wonder how many people even know?

Always remember, you are unique...just like everyone else. :wink:
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a b U Graphics card
September 21, 2004 2:57:41 AM

It is the memory interface, and on a radeon 9550, you want a 128-bit memory interface, not a 64-bit one. Just like on a radeon 9800 Pro, you want the 256-bit and not the 128-bit.


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a b U Graphics card
September 21, 2004 4:09:51 AM

64-bit has half the memory bandwidth of 128-bit. It's the same reason the 9600SE suck so badly compared to the 9600 standards, the same reason the GeForce2 MX200 sucked so badly compared to the GeForce2 MX400, etc.

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September 21, 2004 4:10:00 PM

If memory serves me correctly....

doesnt 64 bit mean 2^64 and 128 bit mean 2^128?

Thats 18446744073709551616 vs 3.40e38

hardly twice the bandwidth, more like a factor of 1.8e19!

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September 21, 2004 5:54:05 PM

Radeon 9550 w/128 bit memory:
Basically a 9600. Can be overclocked to be competitive with the 9600PRO or even XT if you're luck out with good memory.

Radeon 9550 w/64 bit memory:
Basically as fast as a Radeon 9200 or 9600SE. A piece of shite.


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a b U Graphics card
September 21, 2004 7:08:53 PM

No, you're thinking of something else.

For pathways, 64-bit means 64 data traces, and 128-bit means 128 data traces. Or you could just think of them as lanes on a highway. But if you start thinking of them as pipes, you might get confused with the core specs.

Remember that 1 bit is transfered per pathway per transfer cycle. So a 64-bit wide bus transfers 64 bits per transfer cycle. Since the RAM is DDR, that's 128 bits per clock cycle. Using the same concept, a 128-bit bus would transfer 256 bits per clock cycle to DDR RAM.

256 is 2*128. Because 128 is 2*64.

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September 21, 2004 8:44:55 PM

Wow

Always remember, you are unique...just like everyone else. :wink:
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