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Need help understanding S30 memory system

2015-03-19, 7:32 AM

I just purchased a S30 workstation (4352) and intend to replace the existing memory with four 8GB RDIMM modules (one per memory channel). I would like to understand what the limitations are that effect my selection of RDIMM modules so I can avoid doing something silly.

 

The Intel data sheet for the processor (E5-1620 v2) states that it is able to support:

 

   • Up to 8 ranks supported per memory channel: 1, 2 or 4 ranks per DIMM

   • Memory DDR3 data transfer rates of 800, 1066, 1333, 1600, and 1866 MT/s

 

I think the phrase "Up to 8 ranks" means that at some slower speed, perhaps 1333, 8 ranks are supported. But this is very unspecific and in reality how things will work is determined by the systems BIOS. So, I would like to know how many ranks are supported by the S30 with various speed modules (1600 and 1866 MT/s modules of primary interest). Apparently at 1866 speed the number of ranks is way less then 8 as psuturtle states here, where he says that for 1866 MT/s only one module is supported.

 

While this is useful information for people thinking of using PC3-14900 modules, some questions remain. How many ranks can the single 1866 module have? I think 1866 modules have either 1 or 2 ranks as 4-rank modules are not offered at this speed. And what about operation at 1600 MT/s? How many ranks at this speed? Could two 4-rank PC3-12800 modules be installed per channel? Or, at 1600 are 4-rank modules not allowed?

 

Would be nice to have specific information before making a somewhat expensive memory outlay.

 

Thanks.

 

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Re: Need help understanding S30 memory system

2015-03-19, 12:57 PM

welcome to the forum

 

without going too deep into memory architecture, "ranks" are in simple terms the number of DRAM chips connected to the module's controller chip in the center of an RDIMM.   the controller chip (SPI) is serial, therefore the fewer ranks the better down to dual-rank.   dual-rank will outperform single-rank modules by a slight margin.   you aren't likely to find many single-rank RDIMMs anyway.   quad-rank modules are typically larger (but not always) and built as such to save costs.   the same size quad-rank module in dual-rank will typically be more expensive.

 

intel's specs are correct.   ranks can be 1, 2, or 4 per DIMM.   the rest is for the most part inconsequential to rank since any modules you'd be considering will have 4 or less.   memory rank compatibility is set by the memory controller in the CPU and not by the BIOS.

 

it's been a while since i've played with an S30 but i'm sure what psuturtle said about a single channel 1866MHz modules for maximum frequency was correct.   the thread you linked was on a completely different topic so i haven't looked at exactly what was discussed.   if you absolutely need 1866MHz performance then you'll likely have to limit your choices to single channel and either dual- or quad-rank modules.

 

in any case, more info about memory compatibility can be found in the S30 hardware maintenance manual.   for the 4351/4352 machine types, the direct link is here: http://download.lenovo.com/ibmdl/pub/pc/pccbbs/thinkcentre_pdf/s30_hmm.pdf

 

if you can tell us exactly what module(s) you're considering, perhaps we can be of better help.   the details in rank architecture might not even be an issue.

 

(edit: early morning typo)

ThinkStation P700      ThinkPad X1C7

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02-22-2010

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Re: Need help understanding S30 memory system

2015-03-19, 18:13 PM

Since your S30 is an Ivy Bridge (v2) based system, you should be able to run up to 1866MHz memory.  However, to abide by Intel MRC guidelines, if you want to keep your bus speed at 1866, you'll need to run in 1DPC mode.  So for S30 that would limit you to 4 DIMM slots.

 

As far as the ranks, that really plays more into what Intel will support.  At times, Intel will limit the speed/ranks to keep their memory margins in line.  For example, on some of the older platforms, if they detected quad ranked memory, the MRC would drop the memory bus speed by one bin.  That's not the case for up to quad ranked memory with Ivy Bridge class systems as far as I know.  I can't really speak to 8 rank DIMMs off the top of my head (I'd have to go check the spec), but I think you'd be hard pressed to actually find 8 rank parts in the marketplace.




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Re: Need help understanding S30 memory system

2015-03-20, 12:07 PM

I think I am starting to understand how this works. I found something published by Supermicro that appears to answer my questions. It is titled: Memory Configuration Guide - X9 Series Motherboard - Revised Ivy Bridge Update (Socket R & B2), And can be found here. The relevant table is on pages 4 and 5.

 

Given the following:

 

  • E5-2600 v2 (Ivy Bridge) processor and Socket R memory Configuration
  • Motherboards with 8 DIMM slots per CPU
  • RDIMM modules

The table states that within a memory channel:

 

  • A single module with 1 or 2 ranks can operate up to 1866 MT/s
  • A single modules with 4 ranks can operate up to 1066 MT/s
  • Two modules with 1 or 2 ranks can operate up to 1600 MT/s
  • Two modules with 4 ranks can operate up to 800 MT/s

For the 1866 speed the table agrees with what psuturtle says.

 

There are some interesting things about the results shown in the table. Apparently one 2-rank module is not equivalent to two 1-rank modules. Or, one 4-rank module is not equivalent to two 2-rank modules. And it does not cover the case where the total number of ranks is an odd number. I don't think there is anything that would disallow this combination.

 

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Re: Need help understanding S30 memory system

2015-03-20, 12:14 PM

Another question concerning memory and the S30 has to do with what happens if a particular memory configuration gives errors. It appears that the BIOS does not give the user any control over the memory clock rate or other timing settings.

 

Is there any way for a user to respond to this situation other then to replace the memory modules or add additional modules of a lower speed grade?

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Re: Need help understanding S30 memory system

2015-03-23, 20:43 PM

Our system generally follows Intel plan of record when it comes to Romley memory support.  That's why you're not finding many settings to adjust anything....most of the adjustments are handled automatically by the MRC (memory reference code) embedded in BIOS.  

 

I wouldn't necessarily apply info from a supermicro memory guide to our Lenovo platform.  Based on some of the items posted, it appears to me as though they aren't able to fully meet Intel POR support for memory (for example I don't believe our platform will slow down quad ranked 1866MHz memory to 1066).  That's a 3 bin drop, which is telling me supermicro has margin issues when running at full speed and/or high load.

 

As far as I know, Intel looks at single DIMM per channel loading, and  dual DIMM per channel loading when it comes to Romley memory support.  I don't recall any speed drops based on number of ranks for 1866, but I could be wrong about that.  Regardless, single and dual rank probably makes up the large majority of parts in 1866 SKUs.  There might be some quad ranked at higher capacities, but keep in mind S30 only qualified 4GB and 8GB capacities in UDIMM and RDIMM at 1866MHz.  Higher capacities at that speed didn't come along until the product had gone through it's last refresh cycle, so they were never qualfied.

 




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Re: Need help understanding S30 memory system

2015-03-24, 16:01 PM

Yes. The Supermicro guide may not apply to the S30. I referenced this because I could find nothing better.

 

I don't think anyone makes a 4-rank module specified at 1866. 4-rank modules from Samsun and Micron only go up to 1333. Hynix goes up to 1600.

 

Short of buying a bunch of RAM and performing experiments, where could I find definitive information concerning how the S30 and memory modules interact? One would think Lenovo would make this information available - at least for speed grades that were available when the S30 was an active product.

 

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Re: Need help understanding S30 memory system

2015-03-24, 16:14 PM

One more thing. From my reading of the Intel data sheet, it appears that the E5-1620 v2 supports Single Device Data Correction (SDDC). Is this supported in the BIOS of the S30?

 

And if this is the case, should one select RDIMM modules with x4 device organization?

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Re: Need help understanding S30 memory system

2015-03-24, 18:25 PM

I feel like we've pretty definitively covered it already.

 

1866MHz on S30/C30/D30

- follows Intel Plan of Record (POR)

- full speed supported for 1DPC configs

- speed is dependent on the capability of the CPU installed

- only single and dual rank UDIMMs and RDIMMs have been officially qualified (at 4GB and 8GB capacity)

- anything quad ranked or larger capacity is use at your own risk

 

If you have specific DIMMs in mind that you're considering using, post a link and I can take a look for you.

 

 

SDDC is a sub-feature of memory RAS as far as I know, specifically part of sparing.  RAS is supported on S30, and is limited to mirroring and sparing.  There really are no user controlled settings for these features in S30 BIOS.  Supporting mirroring requires you to be in 2DPC configs as far as I know, so it doesn't really play well with 1866 memory support on S30.  I think sparing can be supported in 1DPC configs, but it will end up reducing your available memory as some ranks get marked off for sparing...probably not the best use of memory when your DIMMs are single or dual ranked in most cases.   RAS is really more of a server feature anyway, so not something I'd recommend using on a platform like S30.  I get gather more specifics on it though if you're dead set on using it.




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