I got mine directly from the EVGA forums made by an EVGA employee on his own. It's a BIOS flash that lets you overclock with voltage and allows the card to handle higher core, memory, and shader clocks. You might want to have a back up of your original BIOS because it was created for the EVGA cards and not sure if it works with MSI.
After the flash you can take your card higher in clocks but don't overdue it all at once you may brick your card.
I use EVGA E-Leet Software to do the voltage tweak.
Then I use EVGA Precision Software to tweak the clocks. You can use MSI Afterburner software if you like. Question is will the EVGA BIOS Flash work for the MSI card?
Always start in slow increments when overclocking. Then run an intense game like Crysis in Enthusiast mode AA x4 or any game you have that you can run currently in max settings like Black Ops that you already know works with your GTX 580.
If it works fine without stuttering, video spots, tearing, or freezing then try out a bench mark software like 3D Mark 11 and run it through the benchmarks. IF everything is fine then up your clock setting again like 15Mhz and repeat until you get to a point where things don't work or look right. Once you get to that point back down 15Mhz and you'll know your cards top clock.
One thing I learned is if things freeze up on you the voltage setting and clock settings with go back to factory settings. You have to re-increase your voltage and clocks.
Each card is different in overclocking and it's luck of the draw. Some has to do with cards with better bins like the factory overclocked cards. That's also why you pay a bit more because they've been tested and do better than stock reference cards sold which allows them to be overclocked. Hence why some pay a premium. You can buy the same card cheaper but it doesn't come overclocked and usually doesn't have the same overclock capabilities or limits sometimes, not all the time. I've heard of stock cards doing as well as overclocked cards when overclocking.
I've read people running two of the same exact cards and one getting 950Mhz and another right next to it reaching limits of 875Mhz. Luck of the draw.
Well hope this answers your question. I'd find out before you flash BIOS your MSI card if it works with an EVGA flash BIOS exe made specifically for EVGA cards. It might be universal based on card reference and might not matter.
Let us know what you find out when you do your homework.
I like MSI and EVGA. MSI makes great quality cards. I've owned them before. This a first EVGA card and also the first time I bought the best card on the current market. I'm hooked on EVGA for many reasons now. Great forums, support, warranty, and step up program should a better card come out within 90 days of your purchase anyway. LOL.
Good luck, Happy gaming!