XPS 8950, adding Crucial ram, slot order?

Well, I just checked the 8950 specs and saw that only 2x16GB is supported in the 8950.  Never figured that 4x8GB would not be.

Well, I posted first - researched second.  Bad form.  I know. 

Turns out there are a bunch of previous posts on this forum on this subject.  After reading, it appears that 4x8GB will likely work, although it's not officially supported, and it may run at 4000MHz.

When mixing two pairs of ram (AA+BB), try do dual channel config.  This means pair of identical ram in same color DIMM slots.  the order does not matter.

https://www.intel.com/content/www/us/en/support/articles/000005657/boards-and-kits.html

@billyjk  - If the RAM speed is slow when the 2 pairs are installed as indicated above (use CPU-z, free), try mixing the pairs.

In other words, put the two OEM modules in 1st and 2nd slot from CPU (mismatched retention clips) and install the Crucial modules in 3rd and 4th slots from CPU.  Check speed again...

@redxps630 @RoHe 

Great advice, thanks guys!

If the speed drops lower than 4000MHz b/c I have a mix, or b/c I have a 4x8GB config, I may just return the new Crucial, sell my 2x8GB Dell stock DIMMs (if selling pre-owned DIMMs is a thing), and just get 2x16GB.  I don't think 400MHz is significant, but dropping much more than that may be defeating the notion of having DDR5.

I don't think you'll have any problems using the Crucial RAM along with the OEM RAM, even if you have to mix the pairs.

FWIW, RAM that Dell installs will be from a major manufacturer, eg, Hynix, Samsung, Micron (owns Crucial brand). So I don't think you'd have any problems selling it as "new", and at a good price too, if it comes to that.

Post back and let us know how the upgrade goes.

@RoHe 

I will report back!

Reporting back!

Adding 2x8GB Crucial DIMMs to my stock Dell 2x8GB works fine, just adding the new DIMMs to the 2 available slots.  All 32GB is accounted for and it's all running at 4000MHz.  Got a new question regarding that, if I may...

What is the likely loss in performance that I am now getting between 4400 and 4000MHz, with the addition of the 2 new DIMMs?

My use case is image processing (using AI), audio processing and plenty of typical MS Office and browsing.  I am thinking about trying some gaming, now that I have a machine that is capable.

I would *guess* that there are a number of other significant variables that affect overall performance experienced by a user, and that a 400MHz drop in RAM speed might be down in the noise.  But I am not sure - looking for advice here.

As I mentioned above, I am open to returning the Crucial DIMMs, selling the Dell DIMMs and buying 2x32GB DIMMs that will run at 4400MHz, but I don't want to be wasting time and money if it's not going to have a decent return on the performance front.

I look forward to your thoughts on this.  Thanks!

Memory operating at lower frequency is normally working on better latency as a trade-off (frequency in this sense {+/-20%} is barely performance indicator for the same type of memory).
Or short answer - generally total speed of data exchange wouldn't be noticeable (synthetic tests normally identify between two to five percent difference), therefore it's rather marketing than real 1:1 correlation with frequency vs performance (there's almost no real benefit).
Another indicator worth checking if it is operating in:
(a) true "Double Data Rate",
(b) Command Rate (CR=1)
and
(c) Gear1 (preferable), but depends on CPU (although I guess it's already in Gear2 mode since frequency is lower.

There's free trial of AIDA, it has various benchmarks built-in for measuring memory performance in GB/s (Read, Write, Copy, Latency).


In my experience - I've bought seemingly the same modules ( 2x16GB ) to existing ones (even made sure those are same rank and chip density) which unfortunately went down on frequency too.
Ended up selling original modules (PC was shipped with) and buying another pair of 2x16GB of the same brand (and after replacing it immediately has switched into correct higher frequency operating mode).

@billyjk  Glad the upgrade went smoothy!

While there may be a small decrease in performance at 4000 MHz vs 4400 MHz, (a) I doubt you'll notice, (b) the increase in total RAM installed can likely make up for the slightly lower speed...

@sam55todd 

Thanks for that great insight.  So, you come down on the side of viewing RAM frequency (specifically the 400MHz delta we're talking about here) as not significant to end-user performance.

Not sure yet exactly what I'll do.  My OCD drives me to want the spec I paid for, the more rational side of me says just stay the course.

Well, I can tell you that my OCD already won out.  I have 2x16GB on order from Crucial.  Just don't want to think about it, so I pulled the trigger.

I'll return my Crucial 16GB and put the Dell 16GB up for sale on eBay.  If anyone here is interested in the Dell RAM, just hit me up.  Otherwise, I'll post it on eBay.

Thanks again everyone for your advice!

I don't think you would notice a speed difference between 4000 and 4400 mhz (because both are really fast). It's more about what works and is 100% stable on your motherboard.

The one thing that might make a difference is the ram dimms not running in Dual-Channel as intended. You need an exactly-matched dimm-pair (in a memory bank) for that. CPUID's CPU-Z will report whether it is Dual-Channel or not.

Hard to go wrong with (perfectly matched) Crucial 16gb x2 = 32gb. However, I suggest you don't sell anything until you are sure they are working 100% perfectly for a while. 

@billyjk  - For  the XPS 8950, CPU-Z will likely report on its Memory tab that Channel # is: 2x64 bit, rather than "dual", or 1x64 bit, rather than "single" channel mode.

Chances are good it's running in 2x64 bit (dual) mode, which is exactly what you want....

EDIT: Just saw your last post.  IMO, you're overdoing the OCD, and you're not likely to get any noticeably better performance with 2x 16 GB...

Your PC, your $$, your time...

@billyjk 

I don't know how significant the RAM speed is? I have an 8940, 2930 Mhz speed. I run MS Flight Simulator on a 32 inch monitor @ 3840x2160 resolution which the game run on at 2560x1440. I get great frame rate and other features at full. I recently upped my XPS for 16GB Single Rank DIMMs to 32GB Dual Rank DIMMS. I never saw a DIFFERENCE in any Performance test app I ran that was even more than probably a testing error. MS Flight Sim. did change some settings but more due to the RAM change than anything else. I did NOT notice an VISUAL difference.

I do suspect that if you found an 8940 with similar spec's to what you have the difference might not be much in the day to day tasks you do, but a performance test app might show some differences.

As you said, there are many things that come into play for performance. I'm sure you'll not be able to type faster I suspect for instance it is my video card that is holding back MS Flight Sim more than RAM size or RAM speed.