IT REALLY DEPENDS ON THE RATED SPEEDS OF YOUR MEM!
I have the same card as you but my mem is rated for 715MHz, no more. With the slackest (5950) latencies it did go up to 830, but MSI puts no cooling on the memory chips. With default 5900 timings, it never got above 800, with default 5900xt timings it never got above 740MHz.
Read this thread: http://www.nvnews.net/vbulletin/show...0&page=1&pp=15
before doing something stupid.
BTW, voltages on 5950 and 5900-5900XT are not the same! You will not achieve the same core clocks.
You should edit your bios with simple overclocks on core and memory, the 5900XT has far superior latencies than any other 59XX. There is no real-life gain to slacking latencies (xcept maybe 07 00 0F 40), you would do better to tighten latencies even more as shown in the above thread.
If all you want is higher clocks and more 3dmarks, fine, but I preferred game benches. And Jimmor got the thruth about 59XX.
Also, the 5900xt is not memory bound, it is core bound. You'll achieve impressive results by overclocking the core and tightening memory latencies. The bandwidth of a 5900xt is in excess of 20GB /s. It's the four pipes that f* its performance. That's why an overclock on the core is what's needed.
Again, the Guide to Modding 59XX bios is a complete thread where ALL IMAGINABLE info is and has been verified and confirmed.