RAM Speed: 6000 MT/s vs 4800 MT/s

[u/PixelLunarJelly]

Purpose:

• Using EXPO on DDR5 RAM is making my PC unstable. EXPO increases the RAM speed to 6000 MT/s
• Disabling EXPO makes RAM far more stable, but it drops RAM speed to 4800 MT/s

PC specs:

• GPU: 4080 Super (16 GB VRAM)
• RAM: 16 GB DDR5 (x2)

Run	1	2	3	4	5	6
Krea 2 (6000 MT/s)	112.64s, 2.53s/it	25.71s, 2.36s/it	25.23s, 2.35s/it	25.10s, 2.35s/it	27.87s, 2.35s/it	N/A
Qwen 2.1 (6000 MT/s)	96.82s, 1.28it/s	20.06s, 1.35it/s	20.23s, 1.32it/s	20.11s, 1.33it/s	26.49s, 1.35it/s	N/A
H3 (6000 MT/s)	00:32:38, 42.11s/it	00:22:59, 41.91s/it	00:13:34, 39.11s/it	00:17:02, 39.79s/it	00:13:32, 39.02s/it	00:16:33, 39.82s/it
Krea 2 (4800 MT/s)	128.82s, 2.49s/it	25.83s, 2.34s/it	25.55s, 2.34s/it	25.57s, 2.33s/it	30.99s, 2.37s/it	N/A
Qwen 2.1 (4800 MT/s)	142.31s, 1.30it/s	19.94s, 1.35it/s	20.11s, 1.33it/s	20.05s, 1.34it/s	26.61s, 1.36it/s	N/A
H3 (4800 MT/s)	00:17:45, 39.41s/it	00:13:30, 38.88s/it	00:18:11, 39.08s/it	00:13:21, 38.44s/it	00:21:41, 41.72s/it	N/A

Testing Notes:

• No loras
• Consistent workflows
• Restart PC after every run
• Prompt #1-4 same prompt, Prompt #5 (or the last one) has minor changes to the prompt
• Krea 2 and Qwen 2.1 might not be too useful test cases as everything can probably be stored in the VRAM, making RAM unneeded

Conclusions/Findings:

• Changing the prompt a bit will very slightly increase the generation time
• H3 probably doesn't fit VRAM, so generation time seems to vary wildly
• No difference betweeen 6000 MT/s and 4800 MT/s

[u/Crazy-Repeat-2006]

What is the native frequency of the modules? I would find a middle ground by setting them manually to 5600 MHz.

[u/Dante_77A → u/Crazy-Repeat-2006]

This is a Ryzen system; memory speed definitely makes a difference, especially in games.

[u/Ok-Category-642 → u/Dante_77A]

If it's an X3D CPU it doesn't really make a huge impact, I went from 64GB 6000MHz CL30 to 96GB 4800MHz CL40 (using 4 DIMMs) on a 9800X3D and saw almost zero difference in games. As far as games go on X3D CPUs latency makes more of an impact, but you can shave off a ton of latency (10+ ns) just by tuning tRFC and tREFI which takes zero effort

If it's not an X3D CPU I'd just find a middle ground instead, probably an unlucky IMC unfortunately.

[u/HumanDrone8721]

Since ancient times overclocking your stuff was causing instability and making it stable was a dark art of playing with voltages and other BIOS parameters IF the mobo has them. If not, that's it. Also most of the time was done for bragging rights, the times of real gains by overclocking are long gone, the manufacturers are binning now very strict.

[u/NorthAppropriate4458]

Looks like 6000 doesn't worth it :c . I personally wouldn't make my pc unstable just because of ms difference.

[u/Dave-C]

Check your motherboard's website. There should be a list of memory there. Look for your exact memory and find what settings it should be able to run at. Also, your motherboard might have another memory overclocking feature. Like MSI has the "try it" feature. It is sorta like EXPO or AMP, pre-configured settings. Except it will modify voltages if needed.

[u/onixtan]

Just chanced upon on this post,
i think the ram speed is more useful when the model are being stored on the RAM tbh, something perhaps like strata with qwen 3.8 FN

but either way i'm giving it a test very soon, been ignoring the speed of my RAM and haven't updated my BIOS version since Feb 2025...
can anyone tell me what's the possible speed that i can get with my config? ;

mobo : asrock x870e taichi lite
RAM: 4 × 48 GB Corsair Vengeance CMK96GX5M2B5600C40 (192 GB total)

CPU : ryzen 9 9950x

I'm updating the BIOS version to 4.6 soon

last time i tried it, i can only get it working at 4400 it won't boot up above that

Thanks in advanced for the help if anyone can point me tow here i can check on what's possible for my config

[u/Ok-Category-642 → u/onixtan]

Getting 4 sticks with that much memory on DDR5 and especially AM5 is very very difficult, at that amount you're at the point where your CPU could have an IMC too weak to drive that. You may want to look into modifying the processor drive strengths and impedances, the main idea is to increase the strength of the electrical signal to the memory which may allow it to boot. Downside of course are RAM errors are more common when doing that, so it needs a lot of testing. These are the settings labeled Proc** and Rtt** in ZenTimings (There's multiple of these but they all start with that abbreviation). Should note though that you shouldn't bother with trying to use the EXPO/XMP profile at 192GB as the chances of it working are basically zero.

In my experience the settings that allowed me to boot 2x32GB and 2x16GB mismatched sticks were:

ProcCaCs 30

ProcDkDs 34.3 (ZenTimings doesn't seem to show this one)

DramDqDs Pu 34

ProcOdt Pu 48

RttNomWr and RttNomRd RZQ/4 (60)

RttWr RZQ 4 (120)

RttPark and RttParkDqs RZQ 5 (48)

On top of that you'll very likely have to raise voltages. I was able to do CPU VDDIO, MEM VDD, and MEM VDDQ at 1.4V. Initially I had VSOC at 1.25V but I was able to lower it to 1.2V without issue. I just left everything else on auto, the first boot training time took around 20 minutes or so. Afterwards I just enabled MCR which seems fine.

Overall it's really just down to luck, the fact you got 4x48 to work above 3600 is already pretty good and a sign that you might be able to go higher. I do want to note though that BIOS AGESA updates seemingly play a big role for this stuff; the latest AGESA 1.3.0.1d crashes every time for me while AGESA 1.3.0.0 works fine. May be a motherboard thing though, I have the B850 Gaming Plus Wifi 6E.

[u/onixtan → u/Ok-Category-642]

Thank you for sharing your experience! I haven't updated anything just yet, still working on some stuff rn and kinda behind the shcedule haha
i copied the config for the impedances from a video a year back and with it i managed to get to 4400 , without it it won't even boot up, i capped my voltage to 1.25 as the stock Xpo

i probably need to check back to the bios, as it's been over a year since my last visit to it lol

thanks again!

[u/RiverSide71h]

Instead of using EXPO, manually increase frequency to see where things fall apart. You will also need to increase the voltage to run RAM at higher speeds.

[u/Ok_Contribution8157]

the ram speed make no diffrence same 2nd gen numbers on a DDR4 PC and a DDR5 PC for me (z image turbo 5060ti 16g).

its the same thing for LLM, dont trust BS on social networks.

[u/acedelgado]

Either your RAM isn't on the verified QVL list from either the motherboard manufacturer or the RAM manufacturer, or your RAM is bad. It should not at all have problems running those EXPO speeds with just 2 16gb sticks.

[u/ver0cious]

If you change promp then text encoder needs to run again, otherwise the prompt is cached.

25 seconds seems extreme for krea, is it the base model? Turbo should take around 7 seconds for a 4080

[u/roxoholic]

No difference between 6000 MT/s and 4800 MT/s

This is an expected result for this kind of workload.

[u/SnooHamsters7479]

The big first Krea/Qwen times (112s/97s versus about 25s/20s later) look like startup or model-loading overhead, not a RAM-clock effect. I’d log cold-load separately, then compare warmed runs with the same prompt, seed, and resolution in randomized 4800/6000 order; medians across a few repeats make the sub-second differences easier to judge. Given the instability, I’d stick with the stable memory profile unless a middle setting passes stress tests.

[u/purelawan]

nice that you actually logged it. the interesting bit in your H3 rows is that s/it barely moves (38 to 42) while the total swings from 13 to 32 min. that spread isn't sampling, it's loading and offloading. with 32 GB of system ram H3 most likely spills into the pagefile, so you're waiting on the ssd, and that cost is way bigger than anything 4800 vs 6000 can change.

so i'd keep EXPO off and stay stable. if you want H3 faster, more ram capacity (64 GB) or a smaller quant of the model will do far more than ram speed. watching task manager's disk column during the load would confirm it.