The speed of DIMM is controlled by either the CPU or the motherboard.
The speed of DIMM is controlled by either the CPU or the motherboard.
xXDarkSoul12Xx
07-04-2020, 04:05 PM #1Hello everyone, I'm getting ready for my first PC build and have collected a lot of information. However, some questions remain unclear, and the answers I've found seem to differ. I'm hoping you can help clarify things. My build will use an MSI B550 Gaming Edge Wifi. Here are the details: it has four DDR4 slots, supports up to 128GB, and includes DDR4 speeds from 1866 to 4600 MHz according to JEDEC. It also supports DDR4 speeds up to 3733/3866/4000/4133/4266/4400/4533/4600/4733/4800/4866/5000/5100+ MHz via A-XMP OC MODE. The 2DPC and 2R slots have maximum speeds of 3600 MHz. My main concern is whether I'm restricted to a RAM speed of 3600 MHz because I'll need to place certain slots first. As you can see, the 2DPC slot only goes up to 3600 MHz. I've read that on older systems, the Memory Controller Unit (MCU) set the RAM speed, but now newer CPUs use the Integrated Memory Controller (IMC). So today it's unclear if it's the motherboard, the CPU, or a combination that decides. I've seen all three possibilities mentioned, but no clear guidance seems to exist. This seems like a question that's been asked before, so I apologize if I'm missing something.
Xeioz_miaou
07-05-2020, 07:23 PM #2Determinations come from two sources: the speed listed on the packaging for the RAM is what it performed in a lab, but this doesn't always match real-world results with different boards and chips. Try what you can, since only hands-on testing will reveal the truth.
THE_KILLER_
07-06-2020, 04:12 AM #3You've thoroughly investigated the details, aligning with Jumballi's insights about MCU and IMC. The motherboard maker has confirmed and backed up the performance of four "verified" RAM modules (two per channel dimmed). They can operate smoothly at 3600mhz. The RAM catalog ensures your purchased units match the rated speeds set by the manufacturer. The CPU's IMC receives its own approval from AMD (or Intel) on its specification page, stating a maximum of 3200MHz. Any frequency beyond that is considered an overclock. This doesn't restrict you; the real cap comes from RAM compatibility (3200, 3600, 5000mhz, etc.) along with CPU and motherboard controller capabilities. A speed around 3600mhz fits well within most manufacturers' ranges when four slots are filled, and 5100mhz is mostly seen with 2x8GB or 2x16GB setups. The latest Ryzen 5000 models still list 3200mhz, though release notes mention potential upgrades to 4000mhz; we'll need to monitor their performance at higher speeds.
A kit of 2x8GB 3600 MHZ and not OC'ing any higher would probably be the safe bet, not exceeding any listed limitation for both Mobo and CPU. But even 3600 MHZ (Or other speeds) can be OC'ed to higher frequencies, I hear. There's a lot to learn. I was thinking i'd let all our good Youtube techies come to a conclusion about the new AMD 5000 series before buying my RAM. Gonna be exciting! Just wanted to find head and tail in this. /Networkbear
AmazinglyCool
07-13-2020, 11:53 PM #4Ah this helped, thanks for the replies mates! And yes, this is exaclty related to the new Ryzen 5000 series, hehe. I am strongly considering buying a Ryzen 5 5600x when it releases and I had read that the supposed "sweet spot" would be 4000 MHZ. So I was wondering if I should get a 2x8GB 4000 MHZ RAM kit. I checked the QVL for my Mobo and found a few qualified 2x8GB 4000 MHZ kits. ( https://pangoly.com/en/review/msi-mpg-b5...bility/ram ) - For some reason I could'nt load the QVL on MSI's own site, lol. This had me a little confused, since 2DPC 2R(Slot 4) Channel only goes up to 3600 MHZ. So my take from you're saying is; It is a combination of both MCU and IMC, but I am not really limited and could do my own testing to see what works--? So say the Ryzen 5 5600x has a sweet spot of 4000 MHZ, I could theoretically populate Slot 2 and Slot 4 with a couple of 4000 MHZ RAM sticks (At a risk). It would probably work, since they are not by default set at 4000 MHZ. But when OC'ing to 4000 MHZ, it might even still be OK with the Mobo if the CPU likes it, yes? A kit of 2x8GB 3600 MHZ and not OC'ing any higher would probably be the safe bet, not exceeding any listed limitation for both Mobo and CPU. But even 3600 MHZ (Or other speeds) can be OC'ed to higher frequencies, I hear. There's a lot to learn. I was thinking i'd let all our good Youtube techies come to a conclusion about the new AMD 5000 series before buying my RAM. Gonna be exciting! Just wanted to find head and tail in this. /Networkbear
Sharing my experience with the Zen2 chip on a B450 board versus a B550. On the older board I struggled to maintain stability at 3200Mhz even with Zen2's better thermal performance. It worked in normal use but crashed under stress or during games. Adjusting timings didn't help much. Eventually I sold the 3200Mhz board and used a cheaper 2400Mhz one from a friend who upgraded. Switching to the B550, I got a 3600Mhz kit and enabled DOCP in BIOS. It's been smooth ever since. I haven't pushed it to 4000Mhz, but I've found RAM overclocking to be a lot of effort with minimal real gains. It seems Zen2 on B550 is already capable of handling higher speeds, and Ryzen 5xxx chips could take it further.
_Annabelle_
07-21-2020, 12:27 AM #6Great news! Thanks for the update, that's helpful. Probably the benefits won't be huge enough to justify the effort. We'll keep an eye on things. Likely many more guides will appear soon.
Wicked_World
07-23-2020, 11:03 PM #7I possess the board you mentioned. The MSI B550 MPG gaming edge with Wi-Fi is a solid choice, though be cautious with Bluetooth—it tends to be a bit unstable. I've tested it with 4000MHz RAM; it performed well initially. Currently, I'm using a 32GB Kingston HyperX Fury RGB with 2x16GB RAM, operating at 3200MHz XMP. It's remained stable since installation.
Digideath, thanks for the info! I don’t think I’ll rely on wireless much, but it’s a cool feature. Ethernet is a must. Awesome! Maybe I should buy a 2x8GB 4000 MHZ unit to be able to boost it to 4000 MHZ. We’ll find out what the experts say when the new Ryzen 5000 line hits tomorrow. /NetworkBear