[SOLVED] mixing RAM size and speeds faster than max CPU specs speed.

BW-userx · 01-06-2020, 06:02 PM

I've only encountered the subject of dual channel RAM same speeds advice/info/

Code:

 To take advantage of a dual-channel platform when purchasing memory 
make sure to buy memory in identical pairs. For example, if you wanted 
to upgrade to an additional 2 GB of memory. Buy two 1 GB memory modules 
that are exactly identical. While the speed of each memory chip does not 
need to be the same as the others, it is best to install memory with 
matching speeds. If the speeds differ, the motherboard runs the memory 
chips at the speed of the slowest chip.

source https://www.computerhope.com/jargon/...nel-memory.htm

I've also read that if the MB or CPU max ram speed is say 1233MHz then faster speed is not obtainable. easy enough to understand. But,

I got 2400T 8GB and a 2666MHz 16GB.

Code:

$ sudo dmidecode --type 17
# dmidecode 3.2
Getting SMBIOS data from sysfs.
SMBIOS 2.7 present.

Handle 0x0018, DMI type 17, 40 bytes
Memory Device
	Array Handle: 0x0005
	Error Information Handle: Not Provided
	Total Width: 64 bits
	Data Width: 64 bits
	Size: 16384 MB
	Form Factor: SODIMM
	Set: None
	Locator: Bottom-Slot 1(left)
	Bank Locator: ChannelA
	Type: DDR4
	Type Detail: Synchronous Unbuffered (Unregistered)
	Speed: 2133 MT/s
	Manufacturer: Unknown - [0x4909]
	Serial Number: 00000000
	Asset Tag:  
	Part Number: D1D4S816GB1G81G82666
	Rank: 2
	Configured Memory Speed: 2133 MT/s
	Minimum Voltage: Unknown
	Maximum Voltage: Unknown
	Configured Voltage: 1.2 V

Handle 0x0006, DMI type 17, 40 bytes
Memory Device
	Array Handle: 0x0005
	Error Information Handle: Not Provided
	Total Width: 64 bits
	Data Width: 64 bits
	Size: 8192 MB
	Form Factor: SODIMM
	Set: None
	Locator: Bottom-Slot 2(right)
	Bank Locator: ChannelB
	Type: DDR4
	Type Detail: Synchronous Unbuffered (Unregistered)
	Speed: 2133 MT/s
	Manufacturer: Hynix/Hyundai
	Serial Number: 42285CA6
	Asset Tag:  
	Part Number: HMA81GS6MFR8N-UH    
	Rank: 1
	Configured Memory Speed: 2133 MT/s
	Minimum Voltage: Unknown
	Maximum Voltage: Unknown
	Configured Voltage: 1.2 V

in Linux it states 2133 MT/s for both. in Windows using CPU Z it shows the 16 at 1333 X 2 = 2666 and various speeds ( I'd have to go back into windows and run it again to copy everything over on here).

the question is as it says mixed ram runs at the lowest speed of the two mixed RAM sticks. but it looks to me that if the two sticks are faster speed then the cpu rated max speed it does not matter.

as CPU z shows dual channel is being used in windows, I do not know about Linux. I have not found a method to show me if that is the case in Linux. I assume it should be.

therefore, if the two mixed speeds and sizes are being limited to just 2133 it does not matter if one RAM stick is 2666MHz and the other is 2400T MHz the both looks like to me are being throttled down to 2133MHz and put into duel channel so what I have been reading about is not the real skinny on how RAM works together.

they are all just logical suggestions???

this is a laptop

hp 840 g3
CPU Intel(R) Core(TM) i7-6600U CPU @ 2.60GHz
RAM 23451 MB : 443 : 21613
Graphics Card [HD Graphics 520] (rev 07)

smallpond · 01-06-2020, 07:07 PM

The firmware reads the I2C bus and configures the RAM controller in the CPU before booting the OS, so its unlikely that you will see different information from Windows and Linux.

frankbell · 01-06-2020, 07:13 PM

Most motherboards I've used have very specific specifications as the type/size of RAM sticks and the order in which they should be seated in the RAM slots.

I've found that it does not do to deviate from those specifications.

BW-userx · 01-06-2020, 07:28 PM

Quote:

Originally Posted by frankbell

Most motherboards I've used have very specific specifications as the type/size of RAM sticks and the order in which they should be seated in the RAM slots.

I've found that it does not do to deviate from those specifications.

well before I deeply investigated it. I already knew about the slower speed RAM dominates if mixed. then seen how critical stated that its 2666MHZ RAM is guaranteed to work on a hp 840 g3. then I check the prices on ebay and 16GB 2133 and 2666 were very if not the same prices. so I just got the faster one. Then when I oped it up I seen that even though it said 2133MHz on the software end on the stick it is 2400T .. not really taking everything into consideration seeings how the 2133 and 2666 are the same prices. I just got 2666 because why not get faster if they both are same prices. then ran a beachmark on it again and the ram category went from bad to good with the extra 16 gb ram.

then started reading up on it as Linux reported 2133 speed still and in BIOS too (just checked it a bit ago). but the write ups it seems to me that the actual limitation of speed is depended on the MB or CPU rating of max ram speed.

also read that if mixed sizes say 16GB and 8GB the dual channel will take the other 8 off 16 and dual that leaving 8 as a single. yet with the 2133 limitation it to me does not seem to matter that they are mixed in speeds too, as they both are max out at 2133MHz

mrmazda · 01-06-2020, 08:42 PM

I have to guess the 2666 speed reported by Windows is the speed limit supported by the stick, not the currently operational speed. Linux is possibly seeing the BIOS having limited the speed to 2133 due to the CAS mismatch between the 2400 and 2666 sticks. I haven't had opportunity to test this in a laptop, but reduction below optimal is typical of mismatches on desktops having differing configuration between sticks of same size, such as one single sided and the other double sided. I'm also guessing that dual channel mode is only partially used, the whole of the smaller stick and half the larger running in dual channel, and the other half of the larger not.

I tried to simulate what you reported here to compare to a matched pair, with 4G DDR4-2133 and 8G DDR4-2400. All tests operated the RAM @2400, but no tests reported whether operating in dual channel mode or not.

Code:

# inxi -SCM
System:    Host: ab250 Kernel: 4.19.0-6-amd64 x86_64 bits: 64 Desktop: Trinity R14.0.7 Distro: Debian GNU/Linux 10 (buster)
Machine:   Type: Desktop Mobo: ASUSTeK model: PRIME B250M-C v: Rev X.0x  UEFI: American Megatrends  v: 1608 date: 10/21/2019 
CPU:       Topology: Dual Core model: Intel Pentium G4600 bits: 64 type: MT MCP L2 cache: 3072 KiB
           Speed: 800 MHz min/max: 800/3600 MHz Core speeds (MHz): 1: 800 2: 800 3: 803 4: 800

# dmidecode --type 17
# dmidecode 3.2
Getting SMBIOS data from sysfs.
SMBIOS 3.0.0 present.

Handle 0x0046, DMI type 17, 40 bytes
Memory Device
	Array Handle: 0x0044
	Error Information Handle: Not Provided
	Total Width: 64 bits
	Data Width: 64 bits
	Size: 4096 MB
	Form Factor: DIMM
	Set: None
	Locator: ChannelA-DIMM2
	Bank Locator: BANK 1
	Type: DDR4
	Type Detail: Synchronous Unbuffered (Unregistered)
	Speed: 2400 MT/s
	Manufacturer: GEIL
	Serial Number: 00000000
	Asset Tag: 9876543210
	Part Number: CL15-15-15 D4-2133  
	Rank: 1
	Configured Memory Speed: 2400 MT/s
	Minimum Voltage: Unknown
	Maximum Voltage: Unknown
	Configured Voltage: 1.2 V

Handle 0x0048, DMI type 17, 40 bytes
Memory Device
	Array Handle: 0x0044
	Error Information Handle: Not Provided
	Total Width: 64 bits
	Data Width: 64 bits
	Size: 8192 MB
	Form Factor: DIMM
	Set: None
	Locator: ChannelB-DIMM2
	Bank Locator: BANK 3
	Type: DDR4
	Type Detail: Synchronous Unbuffered (Unregistered)
	Speed: 2400 MT/s
	Manufacturer: CRUCIAL
	Serial Number: E2E9ACF0
	Asset Tag: 9876543210
	Part Number: CT8G4DFD824A.M16FF  
	Rank: 2
	Configured Memory Speed: 2400 MT/s
	Minimum Voltage: Unknown
	Maximum Voltage: Unknown
	Configured Voltage: 1.2 V

MemTest86 V7.4 Free
	CAS:	15-15-15-36
	Size:	11.8G
	Speed:	2134MHz
	Throughput: 22.29 GB/s
>[Note] RAM may be vulnerable to high frequency row hammer bit flips
********************************************************************
# dmidecode --type 17
# dmidecode 3.2
Getting SMBIOS data from sysfs.
SMBIOS 3.0.0 present.

Handle 0x0046, DMI type 17, 40 bytes
Memory Device
        Array Handle: 0x0044
        Error Information Handle: Not Provided
        Total Width: 64 bits
        Data Width: 64 bits
        Size: 8192 MB
        Form Factor: DIMM
        Set: None
        Locator: ChannelA-DIMM2
        Bank Locator: BANK 1
        Type: DDR4
        Type Detail: Synchronous Unbuffered (Unregistered)
        Speed: 2400 MT/s
        Manufacturer: CRUCIAL
        Serial Number: E2E9ACF0
        Asset Tag: 9876543210
        Part Number: CT8G4DFD824A.M16FF
        Rank: 2
        Configured Memory Speed: 2400 MT/s
        Minimum Voltage: Unknown
        Maximum Voltage: Unknown
        Configured Voltage: 1.2 V

Handle 0x0048, DMI type 17, 40 bytes
Memory Device
        Array Handle: 0x0044
        Error Information Handle: Not Provided
        Total Width: 64 bits
        Data Width: 64 bits
        Size: 8192 MB
        Form Factor: DIMM
        Set: None
        Locator: ChannelB-DIMM2
        Bank Locator: BANK 3
        Type: DDR4
        Type Detail: Synchronous Unbuffered (Unregistered)
        Speed: 2400 MT/s
        Manufacturer: CRUCIAL
        Serial Number: E2E9AE17
        Asset Tag: 9876543210
        Part Number: CT8G4DFD824A.M16FF
        Rank: 2
        Configured Memory Speed: 2400 MT/s
        Minimum Voltage: Unknown
        Maximum Voltage: Unknown
        Configured Voltage: 1.2 V

MemTest86 V7.4 Free
	CAS:	17-17-17-39
	Size:	15.8G
	Speed:	2400MHz
	Throughput: 23.88 GB/s

First boot attempt with 4G/8G configuration configuration resulted in black screen with NUM on. 2nd boot this configuration resulted in segfault during INIT, so I changed CMOS DRAM Odd Ratio Mode from Enabled to Disabled, then on next boot normal operation resumed, and continued after I returned the other 8G stick to the slot in which I had put the 4G.

BW-userx · 01-07-2020, 07:36 AM

with all of the so called expert advice on the net, I think a lot of it needs to be removed, it is out dated and or, incomplete, or just wrong (fat chance of that happening).

Quote:

Also note that your motherboard may not run your RAM at its advertised speed out of the box. If you buy DDR4-3600 RAM and your motherboard supports anything up to DDR4-3400, it may still clock it to the lowest setting by default—say, DDR4-3000. You’ll want to head into your computer’s BIOS and set it to the correct speed, either by enabling Intel’s extreme memory profile (XMP) or by adjusting the speed yourself.
Also note that installing non-matching RAM DIMMs (which have different speed and timing ratings) is generally OK—your motherboard is smart enough to handle the different hardware. But in each case, the system will clock down to match the slowest memory module it has access to, so buying faster RAM to mix with slower RAM doesn’t have any real benefit. Where possible, it’s best to match new RAM with old RAM.

Source: https://www.howtogeek.com/303455/how...s-performance/

what most fail to mention and this one waits until the end of the article. They first get your attention that there is faster speeds of ram out there one can use. Because that is what we all want. then at the end of this article it says that Motherboards may not run the rated speed of the RAM, it is determined by the Motherboard. or CPU

Quote:

Originally Posted by Intel

Memory Types
DDR4-2133, LPDDR3-1866, DDR3L-1600

Source: https://ark.intel.com/content/www/us...-3-40-ghz.html

so they should read that the Motherboard has control of the RAM speeds then it is the RAM itself next. if mixed speeds then if they both are faster then the Motherboard it still will not matter, because they both will be reduced to the max limits of the Motherboard.

Yet, with the intel specs of its CPU it should be stated that it is the CPU that limits this speed to a max speed.

should read something like. It does not matter what speed RAM you have if your CPU only supports 2133MHz (or faster, whatever speed does not matter) then that is the fastest you will get out of your RAM that is anything faster then its base rating for max RAM speed. then go into how mix ram speed might limit the other ram speed if and only if they both are lesser then max RAM speed of the CPUs limitation.

NOTE not all BIOS have that XMP thing in BIOS to change RAM speeds, it still falls to the CPU's limitations and not the Motherboards. again a misleading article on this.

Geist · 01-09-2020, 07:39 AM

After having trouble getting my Ryzen 2700 system (non X) to work with all four sticks of RAM I ordered (without doing much research) and it always hung up because, as it turned out, RAM speed was too high for the internal memory controller while also having to juggle four sticks, and it would only work on 2666mhz or something instead of what was it, 4k or something, well.
(I thought it was voltage issues, but even on 'real toasty oh boy oh boy' voltages, it would happen...)

I fiddled a lot and came to the conclusion that it's a meme, it means little, I benchmarked things many a times and the gains from memory speed were marginal at best.
Now, I'm not an expert (and I'm not sarcastic with that, but sincere) so I don't really know what I'm talking about, but it seems that the bandwidth of modern RAM and the MB buses and whatnot are so damn CHUNKY THICCCC that you still get like gigabytes worth of data transferred in what, millisecons/seconds?
Only my SSD even has a chance of playing ball with that, and I mostly run things off a big old harddrive.

Long story short: At first I was concerned about this issue, but now I am free of the fuss and sleep easy with a stable system.
And that at 4ghz undervolted (although I think there's some sort of governnor or internal hardware mabobber that still throttles it somewhat), but all the usual suspects show 4ghz.

So, yeah, I have stopped worrying about RAM speed...

Timothy Miller · 01-09-2020, 07:48 AM

So, this might have been covered, I stopped reading after a few, but:

1. CPU-Z in Windows is reading directly from the RAM's profile, not what it's actually running at. It correctly identifies it as faster ram, whereas reading from DMI you get what the board tells you it is running at.
2. The 2133 is derived from your processor. Skylake (6th generation) processors only officially support DDR4-2133 as their fastest RAM. On a desktop you can overclock the ram, you can't on a laptop (with a few notable exceptions). So it doesn't matter WHAT speed ram you put in, if it's faster than 2133 it'll run at 2133 because that's the fastest the cpu supports.

BW-userx · 01-09-2020, 08:00 AM

@Timothy Miller,

that is the conclusion I came up with. MAX speed is 2133 MHZ due to CPU Limitations. therefore as far as dual channel on ram speeds over that limitation is seems to look like that it will still proved that even if the two sticks are mixed speeds. because one is 8GB 2400T and the other is 16GB 2666MHz and that cpu z stated the 16GB is in dual mode and the 8 is not, and I read that (now days?) if one has one stick larger GB then the other it will match the lesser size and use that amount to dual channel and the left over is set to single. which seems to be the logical thing to do in such cases.

https://www.makeuseof.com/tag/myths-...ons-about-ram/

mostly I posted this because I ordered another 2666MHz stick that well it turns out that I do not actually need to have it, because it does me no good, so now I have to return it as soon as it shows up in the mail. I just wanted to get a confirm on that and rant a little bit because of it too.

thanks to everyone for there input.

Timothy Miller · 01-09-2020, 08:27 AM

Course, if that 2666 is another 16 GB, always nice to have 32 GB instead of 24...

BW-userx · 01-09-2020, 09:10 AM

Quote:

Originally Posted by Timothy Miller

Course, if that 2666 is another 16 GB, always nice to have 32 GB instead of 24...

will I even use that much?

Code:

$ free
              total        used        free      shared  buff/cache   available
Mem:       24013832     1230720    21871544      152508      911568    22125340
Swap:

I just went and got that 16GB 2666 because I wanted to see about the faster RAM and we see where that got me. and I just kept that 16 with the 8 to get 24 . and it does note ven look like I need 24GB where 8 works yet in FreeBSD I had /tmp in tmpfs and was doing stuff in it and it swap failed and that is what made me look into the 16GB. and yeah next weeks episode will be about...

Geist · 01-09-2020, 09:19 AM

I went with 32GB aka 2x16 (aka 4 sticks at 8) because my previous build had 4GB and compilations were awful, I managed to fully use those 32 the other day compiling opentoonz with 16 jobs, so I dialed it down to 14.
...but I think I'll be fine like this for a long time...

So, I guess if you don't do anything memory intensive then most likely not, I rarely go over 3GB on everyday 'just browsing' and so forth, use.

Timothy Miller · 01-09-2020, 10:40 AM

Quote:

Originally Posted by BW-userx

will I even use that much?

Code:

$ free
              total        used        free      shared  buff/cache   available
Mem:       24013832     1230720    21871544      152508      911568    22125340
Swap:

I just went and got that 16GB 2666 because I wanted to see about the faster RAM and we see where that got me. and I just kept that 16 with the 8 to get 24 . and it does note ven look like I need 24GB where 8 works yet in FreeBSD I had /tmp in tmpfs and was doing stuff in it and it swap failed and that is what made me look into the 16GB. and yeah next weeks episode will be about...

Probably not, but always nice to have matched sizes so that you get the most out of dual channel you can.

Only time I've managed to use even 16 GB of my ram is when I have a couple VM's running concurrently. Haven't had my new machine up to 32 GB long enough to have a chance to even try (just upgraded Tuesday), but my old desktop (FX 8320 w/ 32 GB ram) I could manage to use most of it if I had 2 VM's configured for 2 core 8 GB ram running along with a LOT of tabs open in Chromium + Firefox.