Help me understand GPU specs

[cfcboy77]

These days your thrown a plethora of tech specs when it comes to gpu marketing and im getting somewhat confused

So i had a R9 280x but it was artifcating badly so got it refunded and decided to for the R9 290 Gigabyte 4gb version (lovely card by the way).

Now the 280x to me (well on paper) seems like the better spec:

1100mhz core
1500mhz Memory

Where as my 290 has:

1040mhz
1250mhz

So what makes the 290 card that much better, i see a load of specs but they dont really mean much to me, the 280x has far more memory speed and a little more core speed.... What should i be looking for when it comes to defining the true worth of a card and what do these speeds actually mean?

 

[cfcboy77]

As the others have said, benchmarks and reviews are the best way to compare GPUs rather than specs, as these can be misleading.

To actually answer your question though, you're looking at the speed of the core & memory, but that's not the whole story. The core is actually made up of thousands of little processing units, with an infrastructure built around it. The 290 has 2560 of these cores (known as "stream processors" by AMD) where the 280X has 2048 of them. Feeding these cores with information are 160 texture units on the 290, and 128 on the 280X.

I find it easier to work with an analogy - think of the two cards as car engines. The 280X revs higher (core clock speed), but the 290 has a bigger engine capacity (stream processor count) so makes more power even though it's using less revs. The 290 "engine" also has bigger fuel injectors than the 280X engine (the texture units).

The memory is a similar situation - although the 280X memory runs at a higher frequency, the bandwidth is lower than the 290 because the 280X has a 384-bit bus where the 290 has a 512-bit bus. As the graphics card is trying to get data into and out of the memory as quickly as possible, the bus increase more than makes up for the lower frequency. Again, this is like having a smaller, higher revving engine against a larger, slower revving one - the larger one being more powerful in this case.

Also remember that GPUs get improved over time, so a current generation card with exactly the same stats would be faster than a previous generation one. The only thing to watch out for here is when AMD/Nvidia re-use the same generation chip but rename it to the current gen - so a 280X is a renamed 7970, so is a generation older than a 290, and Nvidia's 770 (used to be 680) is last gen where the 780 is current gen. Again, using the engine analogy, a modern 2 litre car is much more powerful than the 2 litre car my dad had 20 years ago.

I know that's a little simplistic, but that's how I understand this stuff. Hope it helps.

Makes sense after this! Great reply