If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Memory and the Ryzen 3000
I'm planning to put together a new computer using one of the new Ryzen processors.
I heard that 3600 MHz memory would provide the best performance for it, because using faster memory would require something to be slowed down to two memory cycles instead of one. Then I learned some more details: the Infinity Fabric interconnect within the CPU runs at half the memory speed, to a maximum of 1800 MHz. So the faster memory even makes the chip work faster internally. However, when looking for a motherboard, some were billed as supporting memory up to 2666 MHz, and others as supporting memory up to 3200 MHz. But when I looked at the *detailed* specs for the latter boards, they _did_ support DDR4-3600 memory... as long as you were overclocking. What? If the memory's rated speed is 3600, how is running it at 3600 overclocking? Is this some multiplier thing, the chip can't get its Infinity Fabric up to 1800 if it stays at its rated clock speed? Or is this just a garble, with the truth not as bad as it sounds: to use the memory at its full rated speed, you will just have to go into the same BIOS screen that people use if they're overclocking, but you don't have to actually overclock anything. Then I found that by buying two 8 GB sticks for my build, I had dodged another bullet! Had I gotten 32 GB of RAM on two 16 GB sticks instead, one web site told me I'd never be able to use it at its rated speed - and I ran a good chance of the computer not booting at all! However, further searching turned up that this was an issue with the first-gen Ryzen, and it got fixed by a BIOS update. Basically, Ryzens didn't like dual- ranked memory, and 16 GB memory sticks are almost always dual-ranked, and 8 GB memory sticks now are almost always single-ranked. Still, apparently there is some risk in dual-ranked memory with Ryzen. I did note that some memory was advertised as compatible with Ryzen, or as compatible with Intel, so I chose, from what was available, something that didn't say it was only for Intel, and which seemed to be on one site's list of memory that did work with Ryzen. In any case, it certainly seems like getting memory for a Ryzen system is a complicated process. John Savard |
#2
|
|||
|
|||
Memory and the Ryzen 3000
John Savard wrote:
I'm planning to put together a new computer using one of the new Ryzen processors. I heard that 3600 MHz memory would provide the best performance for it, because using faster memory would require something to be slowed down to two memory cycles instead of one. Then I learned some more details: the Infinity Fabric interconnect within the CPU runs at half the memory speed, to a maximum of 1800 MHz. So the faster memory even makes the chip work faster internally. However, when looking for a motherboard, some were billed as supporting memory up to 2666 MHz, and others as supporting memory up to 3200 MHz. But when I looked at the *detailed* specs for the latter boards, they _did_ support DDR4-3600 memory... as long as you were overclocking. What? If the memory's rated speed is 3600, how is running it at 3600 overclocking? Is this some multiplier thing, the chip can't get its Infinity Fabric up to 1800 if it stays at its rated clock speed? Or is this just a garble, with the truth not as bad as it sounds: to use the memory at its full rated speed, you will just have to go into the same BIOS screen that people use if they're overclocking, but you don't have to actually overclock anything. Then I found that by buying two 8 GB sticks for my build, I had dodged another bullet! Had I gotten 32 GB of RAM on two 16 GB sticks instead, one web site told me I'd never be able to use it at its rated speed - and I ran a good chance of the computer not booting at all! However, further searching turned up that this was an issue with the first-gen Ryzen, and it got fixed by a BIOS update. Basically, Ryzens didn't like dual- ranked memory, and 16 GB memory sticks are almost always dual-ranked, and 8 GB memory sticks now are almost always single-ranked. Still, apparently there is some risk in dual-ranked memory with Ryzen. I did note that some memory was advertised as compatible with Ryzen, or as compatible with Intel, so I chose, from what was available, something that didn't say it was only for Intel, and which seemed to be on one site's list of memory that did work with Ryzen. In any case, it certainly seems like getting memory for a Ryzen system is a complicated process. John Savard This kind of garble is a motherboard tradition :-/ The info here claims there is some leverage available in the settings. https://www.tomshardware.com/reviews...view,6214.html One setting that varies between 1..2 is "Command Rate". It's the length of time the address and any strobes are place on the command bus. Using two cycles extends the setup time to the second cycle. Because UDIMMs heavily load the address bus, there is more capacitance to drive on the command bus, than the data bus. Using the two cycle setting means a higher clock can be used. With the clock speeds used by modern memories, I don't see how you could run Command Rate 1 any more, even with single rank memory. Using Command Rate of 2, cuts the command bandwidth in half. But when a memory transaction takes 50 or 100 cycles at some god-awful high speed, who really cares at that point ? And with the new split into chiplets, there is an electrical noise benefit. AMD will have more freedom when picking current drive levels for the memory buses. It would appear in the past, they were using low drive (4mA in a 50 ohm environment, instead of a closer match like 8mA). With the multitude of silicon dice, there is more opportunity for splitting power and noise, for doing a different VCore regulator setup and so on. As to exactly how they do that, I haven't seen a mention whether the whole thing runs off one monolithic VCore or not. Anyway, enjoy your new toy. Two sticks of single or dual rank would be a good start. Putting four sticks in, with your emphasis on speed, wouldn't be a good idea. I would not want to disappoint you, with an extended tuning exercise, to make four work at full speed. But setting up two sticks should take you about 30 seconds :-) That was my experience the last time I got to turn on XMP. Check the manual and make sure such a convenience setting exists on your board. When I filled the Test Machine with RAM, configuring that was a bitch. No, it doesn't run at rated speed ... But, on the other hand, I've never seen side effects of a memory error on the Test Machine either. Each generation has a certain mythology about setup, and part of the fun of owning a new motherboard, is picking a popular one, then finding a site like ExtremeSystems and someone who knows what they're doing. At some point, they can assemble a recipe for the best tuning method (i.e. if you go off-track and run the memory 40% faster than you're supposed to). But getting a 3600 rated stick to run at 3600, might be as simple as using XMP. Crack the manual for the new motherboard, and see what they recommend. The CPU has a recommended interface speed at stock. The memory (as specified by JEDEC) has a rated speed, but independent DIMM makers bin the chips and select ones that are capable of running faster than stock. The multitude of clock islands inside the IMC/CPU/membus conspire to quantize ranges of clock rates (in some cases requiring a core clock change or some other setting, to get the best latency). The Tomshardware article hints at this, in a general way. Paul |
#3
|
|||
|
|||
Memory and the Ryzen 3000
On Sat, 20 Jul 2019 12:41:22 -0700 (PDT), John Savard
wrote: In any case, it certainly seems like getting memory for a Ryzen system is a complicated process. Not to ignore existing builds, if you should be lucky to find your component part selections, MB & MEM, within some reviews. I find myself approaching My Motherboard selection for what that is, a MB brand and type, for less of an initial decision permitted outside influences. In a sense the MB is everything. I may also start in on the socket support PDF, running through CPU iterations available from a pulled- and used-sourced aftermarket, before ever getting around considering memory. Unlike memory, though, that I do then select for it, I'll pull and list from available user reviews, to cross-reference it, to their stated experience as satisfactory. New memory, then it is;- I like placing all together, in an order, in case of an issue or (a highly unlikely) sum-total dissatisfied return. Unfortunately, used CPUs off a side market will not fit into that scenario and are a liability. Anyway, memory speeds and overclocking come secondary to overall stability, and that is, likely, at some unstated vantage for price - personally, I usually don't spend much or generally need a lot of physical memory for the applications I'm often on. Thus, the path of least resistance then goes to prove I'm such a Dull Boy if I haven't actually any stringent demands. |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
What B450 MB for ryzen 2200g + 2x4GB kingston hiperx predator? | MaxTheFast | Overclocking AMD Processors | 11 | February 6th 19 09:01 PM |
What B450 MB for ryzen 2200g + 2x4GB kingston hiperx predator? | MaxTheFast | General | 0 | January 18th 19 04:03 PM |
Anyone built a new PC using AMD Ryzen? | Mr. Man-wai Chang | Homebuilt PC's | 1 | July 28th 17 03:17 PM |
[CM] AMD growing again, thanks to Ryzen processors | RS Wood | AMD x86-64 Processors | 1 | July 20th 17 08:56 PM |
AMD Ryzen 7 | Mr. Man-wai Chang | Homebuilt PC's | 1 | February 26th 17 01:34 PM |