Choosing DDR3 double channel slots when installing memory - Page 1
Forum section: electronics / general

author: soldar
author_rank: Super Contributor
timestamp: May 04, 2024, 02:17:17 pm
content: HP Compaq Elite 8300 moboard has four DIMM slots:DIMM1 - Channel B - BlackDIMM2 - Channel B - WhiteDIMM3 - Channel A - BlackDIMM4 - Channel A - WhiteIf I have two DIMMs of, say 4GB and another two of, say, 2GB, how should they go?My guess is 4,2,4,2 as it means both channels have the same 4+2.Is this correct?So blk = 4GB and white = 2 GB?ETA: Shoot! I did it again! I meant to put this in the computing section. Sorry 'bout that.

author: magic
author_rank: Super Contributor
timestamp: May 04, 2024, 03:15:09 pm
content: One screws up channel interleaving, the other screws up rank interleaving within channels. Both will work on most motherboards, though.The true answer is that if you need to ask then it doesn't matter. Unless your motherboard rejects one of those configuration - then you know what to do.Another true answer is that 4GB and even 8GB RAM is so cheap today that this question shouldn't be asked

author: BrokenYugo
author_rank: Super Contributor
timestamp: May 05, 2024, 01:13:41 pm
content: A nice thing about this used enterprise hardware is good documentation, pretty sure last time I had this question about preferred ram arrangement the answer was in the hardware/maintenance manual, given that was a newer DDR4 machine but I bet it's in there.https://support.hp.com/us-en/product/setup-user-guides/hp-compaq-elite-8300-small-form-factor-pc/5232852IIRC it is color=channel and goes the way you think. It will probably run fine either way, worst case it fails POST until properly configured, not a big deal to just try it.

author: m k
author_rank: Super Contributor
timestamp: May 05, 2024, 01:37:17 pm
content: I've found a Fujitsu model series that is not completely ancient, but is still choking.Old combs were 2G and new ones 4G DDR3-800, so not exactly very new construction either.Final outcome was that 2x2G had to be first, maybe overall speed didn't adjust correctly.2x4G had intermittent problems, all configurations were accepted by the manual.Can't remember how module chip count was, but surely that should be taken care of if nothing is mentioned.(since memory read is piped the individual memory cell must be in a correct physical memory chip)(if not then next read to pipe goes to the incorrect physical memory chip that is not ready yet)About the amount of expansion.Industrial stuff has always a dilemma, what money and where.New machine can be very cheap, maybe even a leasing return can be used.But then there is an installation and its cost, and maybe the machine is at best a secondary anyway.So the outcome can be that bean counters are saving from wrong expenses.This time and age can also be very special, W10 is pacing out and change is possibly a bit more than minimal.

author: soldar
author_rank: Super Contributor
timestamp: May 05, 2024, 06:19:32 pm
content: Quote from: BrokenYugo on May 05, 2024, 01:13:41 pmThanks. It is not the SFF but the CMT. I do have the PDF manual but it does not say how to best populate the slots. It saysDIMM1 - Channel B - BlackDIMM2 - Channel B - WhiteDIMM3 - Channel A - BlackDIMM4 - Channel A - WhiteMy assumption is that if I have only two 4 GB sticks they would go in the two black slots (different channels) and therefore, if I add two more 2GB sticks they would go in the white slots. This makes sense to me.I know I can mess around and try. I have a very old double core Compaq GS266AA-ABE and I have messed with it every which way and it will not accept more than 5 GB total even though the modules are all good and in theory it should take 8 GB but the best I can get to work isslot-0 512MiB HYMP564U64CP8-Y5slot-1 2GiB Kingstonslot-2 512MiB HYMP564U64CP8-Y5slot-3 2GiB KingstonIt will not work with 4 x 2GB. It is a mystery but not worth spending time on it.Regarding the Elite 8300 CMT i know I can just test BUT it is not my machine, I would have to guide the owner remotely and the owner subscribes to the (very erroneous) principle of "if it ain't broke don't fix it".If I am lucky I get one shot at this.

author: mariush
author_rank: Super Contributor
timestamp: May 05, 2024, 07:11:44 pm
content: Always populate the slot furthest away from the cpu socket as the termination resistors are closer to that slot. ==== [ 0 ] [ 1 ] [ 2] [ 3 ]1 stick = [ 3 ]2 sticks = [ 1 ] [ 3 ]If all four sticks are single rank, then it doesn't matter. If the 4 GB sticks are dual rank and the 2 GB are single rank, I'd put the 2 GB sticks on one channel (slots 0 and 2) and the 4 GB sticks on the other channel (slots 1 and 3)

author: soldar
author_rank: Super Contributor
timestamp: May 05, 2024, 09:31:31 pm
content: Hynix/Hyundai2GiBDIMM DDR3 Synchronous 1333 MHz (0.8 ns) HMT125U6BFR8C-H9Samsung4GBDIMM DDR3 M378B5173QH0-CK0 1rx8 pc3 12800U 11-12-A1I know nothing about ranks. Unless I see it very clear I think I might wait and buy four equal sticks when I want to upgrade.

author: magic
author_rank: Super Contributor
timestamp: May 06, 2024, 05:04:47 am
content: Quote from: mariush on May 05, 2024, 07:11:44 pmWhy would that be?Did you ever find it to make a measurable difference for any particular workload?

author: mariush
author_rank: Super Contributor
timestamp: May 06, 2024, 06:05:23 am
content: hynix is dual rank :https://www.compuram.biz/memory_module/hynix/hmt125u6bfr8c-h9.htmSamsung is single rank it says so in the title 1Rx8i wrote it wrong in the previous comment ... one channel is slots 0 and 1, the other is slots 2 and 3 ... so if you want dual channel with two sticks, you put rams in 2nd slot of each channel, which would be 1 and 3 (furthest away from cpu socket, in theory you get better signals and potential for higher clocks and lower timings if the sticks are closer to the termination resistors)so what i was thinking on saying is that if two sticks are dual rank and the other two are single rank, i'd try to put the two dual rank on one channel (2nd channel, slots 2 and 3) and the two single rank on the other channel, in the hope that at least one channel can gain some performance increase by using two ranks in a more efficient way.It probably doesn't matter on a system so old, or probably the memory controller doesn't implement this, but on more modern systems like let's say socket AM4 from AMD, the memory controller can gain a bit of performance with dual rank sticks by issuing commands to one rank and do something else with the other rank while the stick is busy with first rank.It's something like this, in a simplified way ... the memory controller sends a request (an address) to read data from or write data to, then it takes some cycles for the ram chips to be ready to read data from, and once they're ready they can send data from that address in a burst .... well the controllers can send a "get ready command" to both ranks, switch to one rank and read the data and in the meantime the other rank is ready to transfer the data and the controller can switch rank and start receiving it, instead of switching rank, sending get ready command, waiting and then receiving ... it's a few nanoseconds of time saved.If you mix single rank and dual rank on a single channel, this scheme may not work, depends on the controller I guess.I don't remember if it was during the DDR2 times or also was the case with DDR3 but some intel chipsets (when they still contained the memory controller) couldn't handle ram sticks made with 4 bit wide chips, while amd controllers could tolerate a wider range of memory arrangementsfor examplehttps://www.ebay.com/itm/266454765280andhttps://www.ebay.com/itm/224578744702, these won't work with some (if not all) intel systems.... while they'll work in AMD systems. that's why they were often cheaper sticks or sold only to OEMs.Usually ram sticks are made with 8 bit wide chips, so you have 8 chips x 8 bits = 64 bit wide, so if you have a ram stick with 16 chips, it's gonna be dual rank, usually one rank per side. But the ram sticks in the link above use 4 bit wide chips, so all the 16 chips on the stick form a single rank.They also make 16 bit wide ram chips, where you only need 4 chips to get the 64 bits it's quite common in laptop ram ... here's an examplehttps://www.amazon.com/3200MHz-PC4-25600-260-Pin-Notebook-M471A1G44AB0-CWE/dp/B08QRZX7B4Some "value" ram sticks were made for desktops as well, and usually used by OEMs to cut costs.Example :https://www.amazon.com/Crucial-2x8GB-Desktop-Memory-CT2K8G4DFRA32A/dp/B08C53LL9J/- there's nothing under the label, only 4 chips on the stick.These are usually slower than x8 ram sticks, LinusTechTips made a video explaining why, I don't remember the reason off the top of my head right now

author: soldar
author_rank: Super Contributor
timestamp: May 06, 2024, 06:40:00 am
content: Thanks. I think I will wait and when I upgrade do it with modules that are all of the same brand and model.

author: magic
author_rank: Super Contributor
timestamp: May 06, 2024, 07:03:29 am
content: Quote from: mariush on May 06, 2024, 06:05:23 amYou still have multiple ranks on each channel, from the two separate RAM modules. If anything, I suppose most people would argue that it's sensible to distribute the ranks equally between channels.However, the "two equal channels" configuration breaks rank interleaving on AMD (the "BIOS and kernel developer's guide" is clear that interleaving requires a power-of-two rank count and ranks of equal size on the channel) and likely on Intel too. In non-interleaved mode the ranks are mapped into address space as two separate blocks, reducing the chance that both will be accessed at the same time under most conditions.

author: wraper
author_rank: Unknown
timestamp: May 06, 2024, 07:25:26 am
content: Quote from: soldar on May 04, 2024, 02:17:17 pmYes, otherwise part of the memory will have lower throughput.

author: soldar
author_rank: Super Contributor
timestamp: May 06, 2024, 07:26:54 am
content: Quote from: mariush on May 06, 2024, 06:05:23 amThe more I look into this the more confused I am.https://www.ebay.com/itm/166730712600Title saysSamsung 16GB (4x4GB)1Rx8PC3-12800U 1600Mhz DDR3 RAM Memory M378B5273DH0-CK0but the sticker in the photo clearly says2Rx8even though the model M378B5273DH0-CK0 should be 1Rx8I think I will let this be.

author: m k
author_rank: Super Contributor
timestamp: May 06, 2024, 09:56:37 am
content: Samsung knows better.Random text is from where ever.Rank is a rank in rank and file, so a row.All chips of a rank are accessed when read happens, next read can happen when chips are ready.So number of ranks is also how many different chip select lines the module has.There are also RAS and CAS, Row and Column Address Strobes, that can be timed as the machine sees fit.CAS Latency CL is also there, so as fast as the machine can do is not how it goes.Module also includes an SPD way of info how it should be treated.Module can have more chip select lines than the motherboard can truly support.But motherboard must have a method to access them all or part of the memory is lost.So rank is the lowest level, next is slot or a file and then channel.It's also possible to have a case where one slot occupies the whole channel.

author: mariush
author_rank: Super Contributor
timestamp: May 06, 2024, 11:02:39 am
content: Quote from: soldar on May 06, 2024, 07:26:54 amIn the picture, the top three sticks are 2Rx8 , the bottom one is 1Rx8 ... you need to be specific and tell the seller to double check them and give you only 2Rx8 or only 1Rx8This seller seems OK, seems to have lots of kits and it's from UK (unless they fake the info) so should get to you faster in Spain :https://www.ebay.com/itm/234230695337It's a bit more expensive but may be worth the time and hassle saved. Should also be able to ask him to give you 4 identical sticks.

author: soldar
author_rank: Super Contributor
timestamp: May 06, 2024, 11:08:19 am
content: Quote from: mariush on May 06, 2024, 11:02:39 amI would have thought the model reference would be enough to completely identify the module but I see the same model can come in different configurations.At this point I think I will just wait and when I decide to upgrade just buy four identical sticks.

author: magic
author_rank: Super Contributor
timestamp: May 08, 2024, 09:35:36 am
content: M378B5273DH0 is dual rank, it says so on the sticker and in the datasheet.The seller is clueless and/or sells a mix of different types.