AMD A-10 6790K memory question

[basslover1]

So I built a new rig not too long ago, and everything went successfully.

I know that AMD APUs are very memory bandwidth sensitive, and of course I disregarded this information. Since my MOBO only has two dimm slots, I figured instead of being maxed out at 2x4 GB sticks, and needing to buy 2x8gb sticks if I ever wanted to expand the system memory it made more sense to go with a single 8GB stick at the time and just upgrade later.

Since then, obviously the single 8gb stick is no longer on sale, but the regular price has increased by $10 bucks to $99 as well.

I acquired some GCs to BB this christmas and I can get a single 4GB stick for 25. The 4GB stick is the same series, same timings and speed but 4GB instead of 8GB.

Question is, with this be detrimental to performance at all? I'm sure it wont be as good as running 2x8GB sticks, but it wouldn't be taking a step back, right? The single 8GB stick is out of my price range right now.

 

[RU482]

what's the speed of teh 1 8GB stick you have?

 

[basslover1]

Sorry thought I mentioned that in my post but its the same stick in my sig; 1866.

 

[Torn Mind]

Running the memory in dual channel mode increases the bandwidth, I believe. The RAM will not run in dual channel mode unless the sticks are the same size, first of all. To guarantee compatibility, you want identical sticks, but sometimes RAM of the same size can be mixed and matched.

 

[mfenn]

Running the memory in dual channel mode increases the bandwidth, I believe. The RAM will not run in dual channel mode unless the sticks are the same size, first of all. To guarantee compatibility, you want identical sticks, but sometimes RAM of the same size can be mixed and matched.

Most boards will actually run in an asymmetric interleaving mode when non-matched DIMMs are inserted. What this means is that the low memory addresses are interleaved between the channels (i.e. dual-channel), but the high memory addresses are just on the large DIMM.

In the OP's case, 8GB of his memory would be "fast" and the other 4GB would be "slow". The catch is that there is no way for the operating system to know about this distinction, so it will allocate memory over both regions. On average, the performance will be about the same because the accesses to slow memory will bottleneck the accesses to fast memory.

At the end of the day, the result is the same, i.e. get another 8GB stick or don't bother.

 

[basslover1]

So what you're saying is that while going with the single 4gb will get me some improvement over my current setup, I'm better off just getting another 8gb whenever it falls back into my price range?

 

[mfenn]

So what you're saying is that while going with the single 4gb will get me some improvement over my current setup, I'm better off just getting another 8gb whenever it falls back into my price range?

Yep, that would be my recommendation.

 

[basslover1]

Thanks!

I'll probably wait a while and hope for a sale. As it stands now, even with the bottleneck on the GPU due to the RAM, this system still outperforms what it replaced so I'm happy as it is.

 

[lehtv]

Well, if you have no need for more than 8GB of RAM capacity-wise, you could try to sell your 8GB stick and replace it with some 2x4GB kit of 2133MHz for minimal cost. 2133 is the fastest your mobo supports. Obviously, if you then needed more RAM later, you'd have to replace them all over again.