Thursday, March 17th 2022
AMD's Robert Hallock Confirms Lack of Manual CPU Overclocking for Ryzen 7 5800X3D
In a livestream talking about AMD's mobile CPUs with HotHardware, Robert Hallock shone some light on the rumours about the Ryzen 7 5800X3D lacking manual overclocking. As per earlier rumours, something TechPowerUp! confirmed with our own sources, AMD's Ryzen 7 5800X3D lacks support for manual CPU overclocking and AMD asked its motherboard partners to remove these features in the UEFI. According to the livestream, these CPUs are said to be hard locked, so there's no workaround when it comes to adjusting the CPU multiplier or Voltage, but at least AMD has a good reason for it.
It turns out that the 3D V-Cache is Voltage limited to a maximum of 1.3 to 1.35 Volts, which means that the regular boost Voltage of individual Ryzen CPU cores, which can hit 1.45 to 1.5 Volts, would be too high for the 3D V-Cache to handle. As such, AMD implemented the restrictions for this CPU. However, the Infinity Fabric and memory bus can still be manually overclocked. The lower Voltage boost also helps explain why the Ryzen 7 5800X3D has lower boost clocks, as it's possible that the higher Voltages are needed to hit the higher frequencies.
That said, Robert Hallock made a point of mentioning that overclocking is a priority for AMD and the Ryzen 7 5800X3D is a one off when it comes to these limitations. The reason behind this is that AMD is limited by the manufacturing technology available to the company today, but it wanted to release the technology to consumers now, rather than wait until the next generation of CPUs. In other words, this is not a change in AMD's business model, as future CPUs from AMD will include overclocking.
Hallock also explained why AMD didn't go with more cores for its first 3D V-Cache CPU and it has to do with the fact that most workloads outside of gaming don't reap much of a benefit. This is large due to how different applications use cache memory and when it comes to games, a lot of the data is being reused, which is a perfect scenario for a large cache, whereas something like video editing software, can't take advantage of a large cache in the same way. This means that AMD's secret to boosting the performance in games is that more game data ends up sitting closer to the CPU, which results in a 12 ns latency for the CPU to retrieve that data from the L3 cache, compared to 60-80 ns when the data has to be fetched from RAM. Add to this the higher bandwidth of the cache and it makes sense how the extra cache helps boost the performance in games.
For more details, please see video below. The interesting part starts around the 45:30 mark.
It turns out that the 3D V-Cache is Voltage limited to a maximum of 1.3 to 1.35 Volts, which means that the regular boost Voltage of individual Ryzen CPU cores, which can hit 1.45 to 1.5 Volts, would be too high for the 3D V-Cache to handle. As such, AMD implemented the restrictions for this CPU. However, the Infinity Fabric and memory bus can still be manually overclocked. The lower Voltage boost also helps explain why the Ryzen 7 5800X3D has lower boost clocks, as it's possible that the higher Voltages are needed to hit the higher frequencies.
Hallock also explained why AMD didn't go with more cores for its first 3D V-Cache CPU and it has to do with the fact that most workloads outside of gaming don't reap much of a benefit. This is large due to how different applications use cache memory and when it comes to games, a lot of the data is being reused, which is a perfect scenario for a large cache, whereas something like video editing software, can't take advantage of a large cache in the same way. This means that AMD's secret to boosting the performance in games is that more game data ends up sitting closer to the CPU, which results in a 12 ns latency for the CPU to retrieve that data from the L3 cache, compared to 60-80 ns when the data has to be fetched from RAM. Add to this the higher bandwidth of the cache and it makes sense how the extra cache helps boost the performance in games.
For more details, please see video below. The interesting part starts around the 45:30 mark.
222 Comments on AMD's Robert Hallock Confirms Lack of Manual CPU Overclocking for Ryzen 7 5800X3D
My 5800x for example is one of the hotter running ones, so a static OC gains me 200Mhz all core, loses 500Mhz single threaded, but also runs 30C colder (well, with 40C ambients it did)
These are simply chips to be left on auto, or with minimal PBO tweaking (curve offset may remain) - and that appeals to a MUCH larger userbase than the overclockers
If you can test your 12th gen in SOTTR 1080p highest with unlimited and 45W limit it would be great :)
Ryzen 5k scales poorly efficiencywise in allcore loads if voltage is above 1.25V-ish (meaning 4.5-4.75GHz allcore depending on bin, CO value etc). I'm not sure where sæefficient scaling stops on 12th gen, but wouldn't be surprised if it were around 1.2-1.3v allcore like Ryzen 5k, maybe lower. My 12400F only runs allcore at 1.0v so can't test scaling on that one.
Igorslab and derbauer ran some tests and adl are insane in gaming efficiency
The only game where I've noticed high power consumption is cyberpunk with RT on at very low resolution to make it cpu bound. Ive seen peaks at 170 watts which is insane for a game, usually its under 100watts in most games.
It seems ADL is very efficient down to around 75W limit or maybe a bit below, but get serious problems at 50W so somewhere between 50 and 75W gamingperformance tanks completely. 5600X at 76W limit is equally efficient as 12900K at 75W.
5800X does not behave the same and scales well at 65W vs stock 142W.
The voltage/frequency curve of Ryzen 5k is a bit weird where you get very good linear scaling to around 1.1v.
My 5600X tested at various speeds, lowest voltage/powerusage in CB23:
4.2@0.99v 56W
4.3@1.02v 60W
4.4@1.05v 64W
4.5@1.10v 69W
4.6@1.18v 76W
4.7@1.26v 95W
4.8@1.34v 115W
I think it is quite comparable to 5800X. All these test were done with 4000 ram so I/O-die uses a bit more power than an avg 5600X.
Even though the I/O-die uses a bit of power (10-15W load 3200MHz ram, 20-30W load 4000MHz ram) the mem controller on ADL, I/O etc uses a fair amount of power, but at the same die as cores.
I bet 12600K will have better perf at low tdp due to less cores/cache.
"From this small sample though, we found that the 5800X3D is slightly faster than the 12900K when using the same DDR4 memory.
It's a small 5% margin, but that did make it 19% faster than the 5900X on average, so AMD's 15% claim is looking good."
Quite an impressive comeback within the generation even without DDR5 support.