memory bandwidth and gpu core question

[chaosmassive]

hi all,

i have this on my mind for awhile

why the manufacturer of gpu always put low bus interface for low end graphic card?
for example HD 6450 got only 64 bit, meanwhile HD 6670 is 128 bit

what happen if HD 6450 got 128 bit or even 256 bit?(assuming it will using exact memory type) will it perform much better?

please explain..
thanks

 

[cars12345]

The higher the bit rate is, the faster the memory and GPU can work together.

Mathematically, I believe that this is 2^64, or 2^1280, or 2^256. This determines the memory bandwidth for one clock cycle.

 

[chaosmassive]

The higher the bit rate is, the faster the memory and GPU can work together.

Mathematically, I believe that this is 2^64, or 2^1280, or 2^256. This determines the memory bandwidth for one clock cycle.

im dont quite understand above number, mind to elaborate more?

 

[cars12345]

The higher the bit rate is, the faster the memory and GPU can work together.

Mathematically, I believe that this is 2^64, or 2^1280, or 2^256. This determines the memory bandwidth for one clock cycle.

im dont quite understand above number, mind to elaborate more?

I believe I am wrong with those exponents, anybody car to shed some light?

The bit rate is the number of actual pins on the GPU's processor. Having double the amount of pins leads to double the bandwidth if the memory clock rate is the same.
To find bandwidth, divide bit rate by memory speed.

 

[chaosmassive]

The higher the bit rate is, the faster the memory and GPU can work together.

Mathematically, I believe that this is 2^64, or 2^1280, or 2^256. This determines the memory bandwidth for one clock cycle.

im dont quite understand above number, mind to elaborate more?

I believe I am wrong with those exponents, anybody car to shed some light?

The bit rate is the number of actual pins on the GPU's processor. Having double the amount of pins leads to double the bandwidth if the memory clock rate is the same.
To find bandwidth, divide bit rate by memory speed.

isnt there a thing called 'memory controller'?
that determined the bus width, my point is of above question is,
what happen if low end gpu has more bus width?

 

[cars12345]

If it has a higher bit rate, but a lower memory speed, the effective bandwidth is the same.

For example 256-bit and 3000 MHz will have the same effective bandwidth as 128-bit and 6000 MHz.

 

[chaosmassive]

If it has a higher bit rate, but a lower memory speed, the effective bandwidth is the same.

For example 256-bit and 3000 MHz will have the same effective bandwidth as 128-bit and 6000 MHz.

i simply didnt get your point,
pls read carefully above question,
i will repeat once again.
for example
6450 64 bit gddr5 @ 800 mhz was 25.6 GB/s
however if it was gddr5 @ 800 mhz on 128 bit interface it will be 51.2GB/s
now my question is= will it get performance increase on 128 bit one?
and why the GPU maker wont make it to 128 bit one for low end GPU???

 

[cars12345]

will it get performance increase on 128 bit one?
and why the GPU maker wont make it to 128 bit one for low end GPU???

To answer your question, yes, you will get better performance on the 128 bit card.
The reason the cheaper one is not 128 bit, is because it is cheaper to make, and is therefore having a cheaper price.