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Old 2015-03-11, 12:09   #1
Jul 2014

3·149 Posts
Default amount of memory when P-1 factoring

  1. 4 x 1.5V DDR3 DIMM sockets supporting up to 32 GB of system memory (Note 1)
  2. Dual channel memory architecture
  3. Support for DDR3 2000(O.C.)/1866/1600/1333/1066 MHz memory modules (Note 2)

Hi, I'm thinking about making my
AMD FX9350 do purely P-1 tests.

Above are the details for the memory the motherboard I've got can use. It's a Gigabyte FX990A-UD3 motherboard.

The best situation seems to be to have 32GB of 2000MHz memory on the board.

I'm posting because I'm wondering if there's any point having that much and that fast memory. Will it be used efficiently?
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Old 2015-03-11, 13:43   #2
VictordeHolland's Avatar
"Victor de Hollander"
Aug 2011
the Netherlands

23×3×72 Posts

Stage 1 uses very little memory, stage 2 uses lots of memory, but can be split in parts at a small speed penalty.
You can also use MaxHighMemWorkers=<number> in local.txt to allow only a few workers in stage 2 at the same time. It's nice to have 32GB, but you don't necessary need it for P-1.
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Old 2015-03-11, 14:17   #3
lycorn's Avatar
Sep 2002
Oeiras, Portugal

145210 Posts

As you have 8 cores on your CPU, you may run up to 8 P-1 tests at the same time, and then it ´s nice to have a great amount of memory available, so you don´t need to limit the memory used by each worker, nor the number of workers using lots of memory (i.e. doing Stage 2) simultaneously.
If you plan to run 8 simultaneous P-1 tests, 32 GB is not too much...

Don´t forget to allocate the desired amount of memory in the Prime95 dialog box (Options -> CPU)

Last fiddled with by lycorn on 2015-03-11 at 14:18
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Old 2015-03-11, 16:41   #4
TheMawn's Avatar
May 2013
East. Always East.

172710 Posts

With 8 P-1 tests, you will definitely be wanting 32 GB over the alternative which is 16 GB. Memory overclocking with AMD has not been a very pretty scene lately, so you might want to throttle that back to 1866 MHz. If a 2000 MHz kit isn't too much more expensive than a 1866 MHz kit, you can buy the 2000 MHz kit but there's a chance you won't be able to run it. You'll probably be fine, though.

If you do decide to upgrade to 32 GB, try to buy it as a single kit (4 x 8 GB) instead of two kits of 16 (2 x 8 GB). Something like this:
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