Question How does gpu memory bus width work?

Jimboss99

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Jun 2, 2016
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Hi all,
I have a few hd 5450s, and I was testing the performance of each one with a different vram size,

Firstly,
The 512mb card has two 256mb chips, 64 bit (10.8gb/s bandwidth gpuz)
The 256mb card has one 256mb chip, 32 bit (5.4gb/s bandwidth gpuz)
They both run at the same memory speed.

Shouldn't the memory bandwidth be the same? wouldn't each chip have 32 bit each?


Secondly,
The 2 gb model has four 512mb chips 64 bit bus
The 1gb model has two 512mb chips 64 bit bus

Wouldn't the 2gb version be slower as more chips are sharing the same 64 bit bus?

Thanks
 

Jimboss99

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Jun 2, 2016
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Bandwidth is solely measured by interface size (how many bits there are) multiplied by the clock speed. It has nothing to do with the number of chips.

EDIT: RAM type may also play a factor. See https://www.gamersnexus.net/dictionary/5-memory-bandwidth-gpu
Thank-you very much, I just have one more thing to ask:
It seems that the 256mb version has the chip missing - there's a space where the chip should have gone - I know you said it's nothing to do with chips but would it be possible that the single chip could be connected to only half of the available memory bus lanes on the gpu? Or am I just overthinking it?
I have pictures of both:


Thanks again
 
Thank-you very much, I just have one more thing to ask:
It seems that the 256mb version has the chip missing - there's a space where the chip should have gone - I know you said it's nothing to do with chips but would it be possible that the single chip could be connected to only half of the available memory bus lanes on the gpu? Or am I just overthinking it?
I have pictures of both:


Thanks again
There's probably more on the other side of the card.
 
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