Asnor

Appreciate the help of everyone. @Mark Kaine helped me look a different direction rather than thinking it could be PBO. And @filpo made me suspect some BIOS settings, that for whatever reason, locked the frequency to 4200 MHz.

Edit: Also thank you @PDifolco. Before that, I wasn't sure if I'm supposed to hit the advertised 4.8 GHz as there was a lot of mixed info on other forums. 
My dumbass did another reply instead of edit, but to be fair, I'm just happy to have fixed this problem after 5 hrs of googling and trying things >.<

It’s actually 4950, and it is, but not with avx or anything.

The Clock ratio being set to 42 was indeed the issue. I did adjust it to Auto and get the expected results now. The CPU also runs 20°C hotter now during the benchmark, around the same temps as the multi core benchmark, which is to be expected I suppose.
 

 
Appreciate the help of everyone. @Mark Kaine helped me look a different direction rather than thinking it could be PBO. And @filpo made me suspect some BIOS settings, that for whatever reason, locked the frequency to 4200 MHz.

Yeah the higher temp is normal. The single core is using quite a bit of power and higher voltage to achieve it's boost.

The Clock ratio being set to 42 was indeed the issue. I did adjust it to Auto and get the expected results now. The CPU also runs 20°C hotter now during the benchmark, around the same temps as the multi core benchmark, which is to be expected I suppose.
 

 
Appreciate the help of everyone. @Mark Kaine helped me look a different direction rather than thinking it could be PBO. And @filpo made me suspect some BIOS settings, that for whatever reason, locked the frequency to 4200 MHz.

If you have virtualization enabled in BIOS and Hypervisor or Sandbox in Windows turned ON (does not have to be running) then you will get reduced BCLK to around 98.00MHz which results in reduced single-core performance as not only the core clock will be affected but also Infinity Fabric and DRAM.
 
Check with CPU-Z if your BCLK is 100MHz or if it fluctuates down to 98MHz. (does not matter if it's set to 100 in BIOS)
 
EDIT:
 
As I see the CPU Core Ratio is locked to 42 which sould be set to Auto, there is no reason it should be manually locked.
Don't set it to 48, leave it on Auto. If you set it to 48 all cores will try to boost to 48 which will make your system unstable as not all cores may be capable of doing that.
 

yea, idk why that is tbh, but certainly weird... it shouldn't be locked at all, maybe a bios thing after all. 🤔
 
(but just try to change it i guess)

Thank you for clearing that up, at least I now know what the culprit likely is then.
 
Okay, big thanks for that. I'll try it during the weekend then as I use this PC for work related stuff too. From what I've seen in the BIOS, the Target CPU Speed is locked at 4200 MHz and the CPU Core Ratio is set to a static value of 42.00. I suppose that is the culprit then? Would the fix be as easy as adjusting the ratio to 48.00? 

Thank you for clearing that up, at least I now know what the culprit likely is then.
 
Okay, big thanks for that. I'll try it during the weekend then as I use this PC for work related stuff too. From what I've seen in the BIOS, the Target CPU Speed is locked at 4200 MHz and the CPU Core Ratio is set to a static value of 42.00. I suppose that is the culprit then? Would the fix be as easy as adjusting the ratio to 48.00? 

That might be the problem because my system wasn't boosting before with my r5 5600 but I updated bios to latest and all was well. Just be sure to not download the latest bios update that's in beta (it will say on the page) go for the one just before (i learnt that the hard way)

yea so thats not how pbo works, its about time not frequency,  and u need to update ur bios its very old
 
 
 
thems the breaks u either want the old bios or better boost,  there's no guarantees about stable here

Those clocks are kinda weird, normally the 5900X reports as 3.7GHz in CBR23 (base clock) and boost to 4.8 (or a bit more) on single core benchmark, at least that's what mine does
I do have PBO and OC+100, undervolt and tweaked PLs but it doesn't change much the score in single core test
 

The 4.8 is only on one core so if its at 4.2 im guessing that best core is at 4.5 so try a bios update unless you have the latest one 

If you buy 2 modules and then decide to upgrade later on with 2 more, they might not run stable when you turn on the DOCP/XMP profile. I think that's the reason why it is recommended to buy a new kit with 4 modules if you wanna avoid the headache of manually tuning the timings. But at that point I would rather just get two 16 GB DIMMs and run with dual channel, provided you have the spare money.
 

Didn't know about Crucial switching to lower quality components, but I recently bought one (8 months ago) and its running fine so far (using it as my Games Storage). I also have an 870 EVO, which funnily enough, was the reason I bought the MX500. 8 Months ago I randomly found an article about early batches of the 870 EVO being faulty, so I checked the SMART values and they indeed reported 2 critical values. The RMA process with Samsung here in Europe thankfully went without pain and the new one is now running well. 

Out of the 2 I'd prolly be leaning more towards the 870 EVO. Never used a SanDisk, so can't chime in on that one.