6GB dual channel vs. 7GB

[deadken]

I recently purchased a refurbished HP DX 7400 PC (http://www8.hp.com/h20195/v2/GetDocument.aspx?docname=c04282603). It came with:
Core 2 Duo 2.66Ghz, 2GB RAM, 250GB HDD, DVDRW, Windows 7 Professional 64 Bit

I'm interested in trying a new bicycle training program and it needed at least Win7. Rather than bring my PC to my trainer, or bring my trainer to my PC I spent a whopping $99 shipped and got a PC that mostly met the specs:
Minimum Specs
OS Windows 7, or OS X 10.9
Processor Intel Core 2 Duo
Memory 4GB
Graphics 1GB dedicated GPU, or embedded Intel HD 4000/AMD R5
Hard Drive 4GB of free space

Recommended Specs
OS Windows 7 or higher,
OS X 10.9 or higher
Processor Dual Core i5 or AMD
Memory 8GB
Graphics 2GB Radeon R9 200 series, or NVidia GTX 650
Hard Drive 4GB of free space

Extreme Specs
OS Windows 7 or higher,
OS X 10.9 or higher
Processor Quad core Intel i7 or AMD
Memory 8GB
Graphics 2GB Radeon R9 290 series, or NVidia GTX 970
Hard Drive 4GB of free space

I knew that I had an additional 2x2GB of Corsair DDR2 laying around. Once I got the PC, I opened the case and added the RAM so that I had 2gb, 1gb & 2gb, 1gb in the four slots (as you moved away from the CPU). I also added a 2GB GDDR5 GT 730 video card.

When I looked around I saw that I had another 2GB stick of ram. So, I started wondering if I'd be better off with 7GB (2gb, 2gb & 2gb, 1gb) over the 6GB. But, I think I'll be losing the benefit of running dual channel. From what I remember, dual channel gave a 3%-5% benefit, but I could be very wrong about that. Also, since I haven't gotten the program (http://zwift.com/index) installed and connected yet, I can't really test it out myself. I did notice how the minimum spec suggest 4GB, but the recommended and extreme specs suggested 8GB. Which suggests to me that the RAM usage tops out below 8GB.

Any opinions on what would be better? Any suggestions on how I should go about testing one configuration over the other?

FWIW: I'm considering buying a Core 2 Quad (Q6700) CPU. I'm also thinking of upgrading the PSU and video card, but I haven't decided how much money I want to dump into this 'trainer PC'.

 

[VirtualLarry]

I would probably go with 6GB dual-channel to start with, and if you find your "Commit Charge" rising above your physical RAM size, then throw the extra in.

 

[Topweasel]

Its typically a terrible idea to mismatch memory, let alone capacities between channels. what i Don't know is if the last gig or the last 3 gigs will only be accessed in single channel mode.

 

[cyclohexane]

why worry so much? If it's for a bike trainer, I doubt 6GB vs 7GB would make any difference.

 

[Insert_Nickname]

I knew that I had an additional 2x2GB of Corsair DDR2 laying around. Once I got the PC, I opened the case and added the RAM so that I had 2gb, 1gb & 2gb, 1gb in the four slots (as you moved away from the CPU). I also added a 2GB GDDR5 GT 730 video card.

When I looked around I saw that I had another 2GB stick of ram. So, I started wondering if I'd be better off with 7GB (2gb, 2gb & 2gb, 1gb) over the 6GB. But, I think I'll be losing the benefit of running dual channel. From what I remember, dual channel gave a 3%-5% benefit, but I could be very wrong about that.

This is were Intel Flex-memory comes into play. Its quite simple really. Your memory controller has two channels. If you populate them with mismatched capacities, the controller will map the capacity of smallest channel to run in dual channel mode, with the reminder in single channel mode.

Hope that makes sense. In this case the 6GB will run dual channel with the last GB in single channel mode.

 

[deadken]

Thanks to everyone who offered a helpful comment / suggestion.

I would probably go with 6GB dual-channel to start with, and if you find your "Commit Charge" rising above your physical RAM size, then throw the extra in.

Sorry that I don't know this but: I'm thinking that in order to do that, I'd hit Ctrl-Alt-Del and then click on Task Manager and look at the 'physical memory usage' graph to see if it ever exceeds 6GB?

why worry so much? If it's for a bike trainer, I doubt 6GB vs 7GB would make any difference.

I'm not sure it has anything to do with worrying. The bike trainer program is still in beta testing and more like a bike game. Since the recommended spec and extreme spec suggested 8GB, I'm thinking that having more than 6 could make a difference. Since I happen to have enough ram to make 7GB, I figured I would ask opinions as to whether the larger amount would trump the loss of dual channel (the way I understood dual channel (not knowing about 'Flex Memory')). I guess the bottom line is: I have extra parts laying around. Why not make the most of them and possibly have a better experience while using this PC / Program?

 

[myocardia]

Or you could spend $25.99, including shipping, and have 4x2GB sticks: http://www.newegg.com/Product/Product.aspx?Item=N82E16820231203

 

[deadken]

Or you could spend $25.99, including shipping, and have 4x2GB sticks: http://www.newegg.com/Product/Product.aspx?Item=N82E16820231203

I could. But, I really think I'd likely be way better off spending $30 on a used Q6700 Quad core CPU from Ebay instead of spending $26 to get 1GB more RAM.

My question was because I already have the RAM needed to do 7GB (free upgrade). I wasn't sure if going from 6GB to 7GB would be an 'upgrade' since I thought I'd be losing the benefits of dual channel.

 

[myocardia]

I could. But, I really think I'd likely be way better off spending $30 on a used Q6700 Quad core CPU from Ebay instead of spending $26 to get 1GB more RAM.

You're probably right about that, since it seems that the software is written to be able to benefit from up to 8 threads.

My question was because I already have the RAM needed to do 7GB (free upgrade). I wasn't sure if going from 6GB to 7GB would be an 'upgrade' since I thought I'd be losing the benefits of dual channel.

Well, it wouldn't be an upgrade, unless you are actually using more than 6.00 GB. You do lose out on having synchronous dual channel, by not having matching-sized sticks. Thing is, going from 6GB of synchronous dual channel to 6GB of non-synchronous dual channel costs you almost zero performance. Like maybe 1% or so.

Running out of RAM, and having the entire game/simulation grind to a halt for 1½ seconds, while it uses your hard drive as if it were RAM, is considerably worse, I'm sure you would agree. Thing is, that won't happen until you run out of RAM, and the second you do, you'll know about it. If it were me, I'd buy both the $30 Q6700 and the $25 stick of RAM, but if you're only going to do one, buy the quad core, and run 7GB of system RAM in it. With 7GB, only 1GB will run in single channel.

 

[tweakboy]

I dont think you can do this OC.