Originally Posted by snoop234
My mainboard is the "Gigabyte GA-MA790FXT-UD5P"
CPU is : AMD Phenom II x4 955BE
before I buy the ram, i wanna be sure that my machine can actually handle the 32gig and that i can use it with a programm running on an 64bit jvm.
I think you are ignoring the big difference between physical memory and virtual memory.
You want to know how much physical ram your motherboard can use. But asking how much physical ram a 64bit jvm can use is pretty much meaningless.
A process uses virtual memory. It does not directly use physical memory. The kernel uses physical memory as a resource in implementing the virtual memory.
You might reasonably want to know how much virtual memory a 64bit jvm can use. I think that is controlled by parameters you can set, but I don't recall the details. An ordinary 64 bit process can use a nearly unlimited amount of virtual memory, but I think the jvm has limits designed into it.
Before buying more ram, you could increase your swap space and then try whatever jvm based operation you think should use more ram and distinguish between four likely results.
1) The JVM refuses to allocate enough virtual memory and the operation fails. So you need to identify and adjust jvm parameters before more ram would be usable.
2) The large operation works correctly with acceptable performance using swap space. Even if much more than 12GB of virtual memory is used, the access pattern might be localized enough that paging overhead is insignificant and swap space is almost as good as ram.
3) The large operation works correctly using swap space, but is unacceptably slow, but you look at swap in stats and see that paging is a not a significant component of the slow down. Then you know you need to improve the algorithm of whatever big jvm based operation you are running before more ram would be useful.
4) The large operation works correctly using swap space, but is unacceptably slow, and you look at swap in stats to verify that paging is a significant component of the slow down. Then you know that more ram would actually be useful.
As for how much ram a Gigabyte GA-MA790FXT-UD5P can support, I haven't a clue. I was burned years ago by a Gigabyte motherboard which was advertised with many misrepresentations of its actual capabilities, including overstating the amount of physical ram it supported. I haven't bought any Gigabyte products since then and so know nothing about the capabilities of their current products.