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Tell HN: Impact of using 1 or 2 sticks of DDR5 on a 6800HX with 680M IG
56 points by guilamu on Feb 15, 2023 | hide | past | favorite | 34 comments
A few months ago, I ordered a Minisforum UM690 for work.

For less than 500 bucks, this little beast is equipped with the incredibly powerful 8 cores / 16 threads Ryzen 9 6900HX (4.9GHz) and an integrated RDN2 680M graphics card (the single thread performance of this mobile CPU is just 10% lower than my home 5800X desktop PC).

I do some light gaming on my lunch break, and I was pretty impressed by the gaming performance of the 680M.

Because of budget constraints at the time of ordering, I could only afford a single stick of Gskill - RipJaws 16 Go DDR5 4800 MHz CL34.

I made a few benchmarks on multiple games, but most games I play do not come with a proper benchmark loop, so I used Unigine Superposition Benchmark to make a proper benchmark.

Single 16 GB stick, 1080p, medium settings: 3022 (18.85 min fps, 22.61 avg fps, 31.85 max fps)

Those results were good for an IGPU, but I saw a few articles saying that having two sticks instead of one could improve performance (never backed up with benchmarks or hard numbers).

So I bought another stick. Here are the results with two sticks:

Dual 16 GB sticks, 1080p, medium settings: 4969 (31.66 min fps, 37.17 avg fps, 48.96 max fps)

Yep, this is a whopping +65% with two sticks!

So, if you use a CPU with an integrated graphics card, you should use 2 sticks!

Are people these days not generally aware of the difference between single-channel and dual-channel RAM configurations?

Well, the impact is far less noticeable on a configuration with a dedicated GPU.

The diffrence is surely not 65% and in fact barely visible: https://techguided.com/single-channel-vs-dual-channel-vs-qua...

What's interesting here imho, is the staggering difference it makes on an CPU integrated GPU (which makes sense since the GPU is using the comptuer RAM instead of its own RAM).

Also, we've been told DDR5 had built-in dual channel on a single stick so I was not sure this would make any difference at all.

> Also, we've been told DDR5 had built-in dual channel on a single stick so I was not sure this would make any difference at all.

It's really necessary to start thinking in terms of the total width of the memory bus. DIMMs have a 64-bit wide connection. Dual-channel used to only mean half of your DIMM slots were on channel A and half of them were on channel B, for a total of a 128-bit wide memory bus if you populated both channels.

DDR5 splits the DIMM's 64-bit connection into two sub-channels of 32 bits each. But mainstream CPUs still have the same 128-bit total width for their DRAM controllers, so you still need more than one DIMM installed to use all the (sub)channels provided by the CPU's memory controller.

Comparing the 128-bit wide memory bus against the bus widths used by discrete GPUs (and comparing the memory clock speeds) makes it much less surprising that running integrated graphics in a crippled 64-bit wide memory configuration would be problematic. Graphics is a very bandwidth-hungry task.

Thanks for clarifying that, this is some very technical knowledge I did not had!

https://greatpcreview.com/guides/cas-latency-vs-ram-speed/ If you learn about latency and RAM timings, and also how the processor/CPU interacts with memory via the controllers and kernel then you get a much deeper and valuable understanding. Most people confuse “correct configuration” with “more powaaa!”

By analogy: you have now tuned your car and it is running properly. It’s not that it has “more horsepowaaaa!” But rather it can utilize the power it does have effectively.

I get it. So you're saying my car was missing half of the spark plugs, right?

Even if both channels are populated, there can also still be additional benefits from bank interleaving - where you have two memory ranks per channel - particularly on AMDs Zen architecture family (but Intel as well).

Gamers Nexus backed it up with a 27 minute video in late 2020, with plenty of benchmarks to demonstrate that there can be measurable improvement from bank interleaving. https://youtu.be/-UkGu6A-6sQ

Most people will probably think you're talking about rams as in the animal, or maybe the truck.

Computer literacy is on its way down, not that it was particularly high in the first place, so it's foolhardy to just assume some random Joe would know what a computer is, let alone RAM, let alone channels.

Well, I really meant "HN readers" when I said "people". Totally agree with your point though. Kids don't think technology is cool anymore. When I was growing up even the jocks knew how to burn a CD or put a file on a flash drive.

I recall reading some post on a programmer's blog a couple years ago. He lost all his data because he didn't know how to run backups properly; he was the kind of guy who would call over a friend to help him fix something as trivial as badly seated RAM (he wouldn't know it was something trivial, obviously).

Yes. That is a programmer with literally no knowledge of what a computer is or how it works, even at a very rudimentary level.

Ever since I've been careful to never assume anyone knows anything about computers until they demonstrate otherwise, even in a seemingly techy place like HN.

> Computer literacy is on its way down

Perhaps it depends on your definition of "Copmuter literacy", but do you have any evidence to back up that claim? I find it surprising.

Apparently, university students nowadays don't know what files and folders are.[1]

[1]: https://news.slashdot.org/story/21/09/27/2032200/students-do...

People seem generally unaware of the difference between number of channels, width of channels, and number of dimms.

In fact this question is wrong, or at least misleading. The OP went from one DDR5 dimm (with two 32 bit channels) to 2 DDR5 dimms with a total of 4 32 bit channels. Thus doubled the bandwidth, but also doubled the number of memory quests you can have in flight.

Given that GPUs in general are quite bandwidth intensive, not surprising that graphics performance significant increased. This is the main reason why the M1 pro -> M1 max doubles the memory bandwidth, it doubles the iGPU performance in many cases.

I heard of that but never had a chance to do some testing. Is dual-channel good for gaming only or for everything?

It increases RAM bandwidth for everything, but RAM bandwidth isn't the bottleneck in a lot of applications, so you might not see a benefit.

Everything. Dual-channel RAM has essentially double the memory bandwidth of single-channel.

I've noticed the same with my Asus TUF laptops. I've had 2 generations of the 15" models with Ryzen processors and adding a second stick seemed to "wake" them up in a noticeable way. They Ryzen memory controller really seems to benefit from memory running in DDR mode (2 sticks).

> benefit from memory running in DDR mode (2 sticks).

That's not what DDR means. DDR means transferring data on both the rising edge and falling edge of the clock signal. That's true no matter how many chips or modules are involved.

You're thinking of running memory in a dual-channel configuration, which requires two modules but is not synonymous with using two memory sticks, because using both channels also requires putting your two memory modules in the correct slots so that you don't have two modules sharing one channel.

This is fine to post, but not as a Show HN - see https://news.ycombinator.com/showhn.html.

I've done a s/Show/Tell/ on the title so it's fine now.

All right, my bad.

Going from 2 sticks to 4 sticks on my threadripper drastically improved thoughput so yes, always a good idea to max out the channels. I'm just happy I still have 4 more to fill but I probably won't need that much extra memory for years to come.

Same thing with intel. 11th gen (and 12th gen) laptops with integrated graphics come with this disclaimer [1]

> Intel Iris Xe Graphics capability requires system to be configured with dual-channel memory. On the system with single-channel memory, Intel Iris Xe Graphics will function as Intel UHD Graphics.

[1] https://psref.lenovo.com/syspool/Sys/PDF/ThinkPad/ThinkPad_E...

I considered buying one because of this post, but https://store.minisforum.com/ unfortunately seems to be down right now.

It's working fine right now. If you have any pre-buy questions, shoot.

How are the thermals under load? I would like to buy one of these for gaming and I am reading some horror stories on reddit about high temperatures and throttling of RAM and SSD. It seems the QA is all over the place (liquid metal not applied correctly, running all over the motherboard). I would get the preassembled version, not the barebone, but I am still a bit reluctant.

Thermals are what you choose them to be, pretty much. The whole thing is capped at 80°C. It will throttle after that.

In the bios you can select the CPU wattage from 28 to 58 I think (I won't be at work for the next two weeks so I can't say for sure). So If you select 28 watts you'll never hit the temperature limit, if you select 58, you will for sure.

Considering the power I'm getting out of it, I think the liquid metal was properly applied, but I can't know for sure without taking it appart.

Has little to do with the ram and much more to do with your processor and how it handles caching and memory channels, especially considering you were using integrated graphics. (Which would be cached where?)

You replaced a single 16GB RAM stick with 2 8GB ones, right?

Nope, I just added another 16 GB RAM (32 GB total), but the UNIGINE testing I'm doing here is using 1.5GB of VRAM and basically no RAM at all, the results would be the same with 2x8GB or 2x32GB (but I see your point, it's not very "scientific" to replace 16GB by 32GB).

When you say

> Dual 16 GB sticks, 1080p, medium settings: 4969 (31.66 min fps, 37.17 avg fps, 48.96 max fps)

Do you mean 32 GB in total?

Yes, I do, and as I said in another reply: I just added another 16 GB RAM (32 GB total), but the UNIGINE testing I'm doing here is using 1.5GB of VRAM and basically no RAM at all, the results would be the same with 2x8GB or 2x32GB (but I see your point, it's not very "scientific" to replace 16GB by 32GB).

Did you clock the RAM correctly? Enable XMP/EXPO? What timings and clocks is it running on?

Yeah, no, the UM690 BIOS is pretty basic.

4800 is the slowest possible clock speed for DDR5.

You can "overclock" RAM in the BIOS but just by changing 4800 to anything up to 6000. You can't setup timings or voltage so this is pretty useless imho (I tried 5000/5200/5400 all resulting in instability after a while).

Thanks for posting this. These new systems that can expose a PCIe slot are extremely impressive.

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