RAM REQUIREMENTS ON-MOTHERBOARD
The equivalent amount of system RAM as for the sum of all the vRAM used by the GPUs is required when mining with reaper. For instance, 3x 5970s mining with thread_concurrency values of 8000 each would require 3x 500MB = 1500MB system ram (plus additional RAM for the OS). The memory requirements for 7xxx cards are also higher because of larger thread_concurrency values, for instance a thread_concurrency of 24000 means 1.5GB system RAM per card is required.
You shouldn't need a lot of RAM for cgminer, it offloads it to the GPU unlike reaper which for some odd reason keeps it in the system RAM. reaper is coded really sloppily while cgminer is pretty immaculate.
So I am trying to figure out how much memory will I need for two rigs, mining
only with cgminer:
First rig: 4 x 5870 and 1 x 6990 with 2GB RAM already on the motherboard
Second rig: 4 x 7970 ......................with 2GB RAM already on the motherboard
Can you give me an estimation?
Thanks.
2GB for the first rig is fine as long as you are only using cgminer.
With the 7970s, you're going to want to use reaper to achieve the highest hash rates at the lowest possible power consumption. You will need ~1.5 GB * 4 = 6 GB + 1 GB system = 7 GB RAM minimum. Although, you can use 2 GB and cgminer if you want, I just overall much prefer reaper for 7xxx series. 8 GB of RAM is only $40 now, so.