What makes a good mining card?

[Stoneysilence]

I am new to this so I don't know what I am doing really.

But I was wondering if anybody has figured out exactly what on the video card makes it so good at mining?

For some examples, I was looking at some video cards like the 7950 and others and noticed sometimes the manufacturer (IE MSI, Asus, etc...) would tweak things to differentiate themselves from the rest.

Some of the things I saw different was most cards were 128bit, while one would be tweaked to be 256bit.

Another had more shaders than the others.  Some had more onboard memory.

How do all these things affect the hashrate is my ultimate question.  Would I bet better off buying that special card that has 256bit bandwidth over the 128bit versions?  Would I be better off with more shaders? Or ram?

Is there anyway to look at the specs of a card and kinda figure out what it's hashrate would be? Or is it all wait until some sucker buys it and tries it?

[crazyates]

Read this:

https://en.bitcoin.it/wiki/Why_a_GPU_mines_faster_than_a_CPU

[Stoneysilence]

Read this:

https://en.bitcoin.it/wiki/Why_a_GPU_mines_faster_than_a_CPU

So if I am reading that right then the real key is the number of shaders and the clock speed.  So If I was looking at a card that 128bit memory bandwidth that wouldn't have any bearing on the hashrate being different with it's 256bit cousin if all things are equal?

[Bitsaurus]

For mining bandwidth is irrelevant (not much data moved around).  Shaders and clock rate are key.

But you must consider that GPU mining for BTC is almost at an end (considering it ha a good run for over 2 years).

Almost all GPUminers will switch to Litecoin or some other Alt.

Some cards are better than others for Litecoin, so if you're going to start now focus on picking a good Litecoin card.

[Stoneysilence]

For mining bandwidth is irrelevant (not much data moved around).  Shaders and clock rate are key.

But you must consider that GPU mining for BTC is almost at an end (considering it ha a good run for over 2 years).

Almost all GPUminers will switch to Litecoin or some other Alt.

Some cards are better than others for Litecoin, so if you're going to start now focus on picking a good Litecoin card.

Yeah, I already switched to Litecoin with my junky GTX 460.  But I was hoping to be able to tell by looking at a new AMD card if it was going to be a good miner without having to wait for somebody to buy it and try it and post the hash rate.

I am saving up to buy a 7950 to replace my 460 and then will eventually buy another 7950 to put into my system.

[Gator-hex]

AMD/Ati, thousands of stream processors, a large cooler, and many fans.