Which software can offer accurate GPU load test

Which tool will be best for finding out a gpu load test. I have a few cards with me. I want to find out which one will be great for making a custom gaming build that I am going to sell. It is a used one but the only thing I have to add is a graphic card. I had attached one by one all three cards and the output looks almost the same. Here I am selling the pc in the name of gaming so I have to put the card that will work fine. I had seen online reviews which are quiet confusing. This are all old cards from Nvidia and ATi. Two among them were never used. So I want to run the load test to find out what will be the best here.

You are talking about the benchmarking thing. Even if you can provide the models of your all three card it will be easier for people to offer you the right answer. But still you can try out using software like FurMark. This one is a nice gpu testing software that can give you a ideal output of your systems performance. Just install this and run the test and checkout. At the end you will get report and you can simply compare that to find out which one is the best here to give you long lasting output. I had used this tool many times to find out the actual output a graphic card. It is worth to use when you are having multiple gpu.

There are very few tools for gpu testing. There are ample of them that can test the cpu and overall pc. But only for gpu there is very less option available. GpuTest is the one that I think can give you proper solution. You can also go with a manual check by installing the latest game and playing it at the maximum resolution.If the game works well then the card is capable of giving you a stable output. But if not then you can keep that card aside. With stress test you will get a score that you can use to compare with other gpu models. I think manual testing will be lot more effective then going to with the tool.