An easy way to tell what type of memory you have without removing the heatspreaders are by looking at the manufacturer's default speed/timings. In this case the Patriot eXtreme PC4800 DDR memory is rated to run at 600 MHz with 2.5-4-4-8 timings which indicate that they use Samsung TCCD memory. Only Samsung memory can run at such high speeds and to achieve that, timings have to be loosened.
Virtually no Winbond memory (at least not in large quantities without 3.6V+) can run 300 MHz and most do not react very well to such lax timings, I have a set of older BH5 which won't even boot if I tried those timings. Winbond based memory usually come in at the lower end of the speed scale and never have a rating than PC4000.
Psyleck seeing as how you use Samsung memory I wouldn't push the voltage past 2.8V, it doesn't like it in general.
I checked for you, assuming its the same stuff, Patriot extreme performance 4800xbl is warranted up to 2.9v
Manufacturers can't tell how much voltage has gone through the memory if you RMA them.