[ale] 2 questions memory related

Mon Jun 20 09:45:44 EDT 2011

On 06/19/2011 09:23 AM, Greg Clifton wrote:
> I've been selling/building PCs for over 20 yrs and I can tell you that 
> modern memory is way better than it used to be. Not directly related 
> to Moore's Law but linked to it as a result of improvement in process 
> control & machinery used in making the RAM. BTW, Apple never used 
> parity RAM in their PCs (probably do in their servers, esp the Intel 
> based stuff but have 0 experience with those) but IBM PCs did. This 
> was supposedly to increase accuracy or at least to trap errors. 
> However, it turned out that the biggest source of RAM errors was from 
> radioactivity in the ceramic that the chips were packed in. Once 
> plastic/epoxy packaging was developed, RAM errors went WAY down. These 
> days you never see parity (now know as ECC) RAM except in servers and 
> it is generally associated with REGISTERED memory in machines with 
> >24GB of  memory. Both Intel Nehalem family chips (Current generation 
> Xeons and i3, i5, i7) and AMD 6100 & 4100 series CPUS w/ built in 
> memory controllers can support either REG (not so much with i3 and i5 
> and at least some of the i7) or NON-REG RAM. REG is usually required 
> for installations over 24GB because of bus loading.
>
> Also, as a rule of thumb, it is OK if your memory can run faster than 
> your memory clock, but not the reverse. I don't know it for a fact, 
> but suspect that most modern memory has much wider tolerances than 
> what it is sold as which is partly responsible for the fact that we 
> rarely see memory errors on new systems. You are quite right regarding 
> overclocked systems needing better matched parts, and of course better 
> cooling (think water cooled, although at a recent vendor showcase the 
> Kingston rep said that the water cooled memory that they sell is 
> mostly for show and that their modules with metal fins actually cool 
> better).
>
> The main reason for matching RAM was to have matched modules in each 
> memory channel back when systems had dual memory channels. Current 
> systems have either dual, triple or quad channel memory and memory 
> modules should still be installed in sets of 2, 3, or 4 accordingly. 
> Now in a dual processor system, you could have different spec RAM on 
> each CPU with no problem since each CPU has its own memory controller. 
> But as a practical matter in a new build, that would probably never 
> happen.
>
> One final note, again due to bus loading, when a modern system is 
> loaded with memory modules, the memory clock automatically slows down 
> to make the system more reliable.
>
>
> On Sat, Jun 18, 2011 at 8:33 AM, Scott Castaline <skotchman at gmail.com 
> <mailto:skotchman at gmail.com>> wrote:
>
>
>
>     On Fri, Jun 17, 2011 at 1:05 PM, Greg Clifton <gccfof5 at gmail.com
>     <mailto:gccfof5 at gmail.com>> wrote:
>
>         The installing/replacing memory in sets is basically due to
>         older [but not too much older] motherboards ran dual channel
>         RAM [new Intel 2P and some 1P is Triple and AMD is Quad
>         Channel] and you don't want to mix RAM with different specs in
>         the same channel. Also, possibly the manufacturer figures if
>         one module failed it's 'partner' is apt to go soon so just
>         replace both instead of having two trouble tickets to deal
>         with stretched over several weeks. 
>
>     That part I've got, the pairing, what I had the impression of was
>     when you bought like 4 sticks like I had you had to buy all four
>     as a set, not just say buy a pair and then add another pair (same
>     exact one as the 1st pair) later to add on. It didn't make sense
>     to me unless if you're going to push things to the extreme with
>     overclocking and such, then you need "handpicked" components,
>     which for some reason I was under the impression that was what the
>     mfgs were saying for all cases. It was like when I worked at
>     Harris back in the late 70's they had developed a system code
>     named 2C which had it's clocking set up to push TTL to it's
>     extreme limit producing ECL speed (25nsec windows). All chips for
>     that system had to go through special screening for handpicking
>     for the 2C, this was the impression I had got of current memory
>     buying practices. I don't want to give the impression that I don't
>     understand that you have to buy in at least pairs and that all
>     sticks have to have the same specs. I personally would stick to
>     the same make/model as what I already have.
>
>
>         On Fri, Jun 17, 2011 at 12:24 PM, Michael B. Trausch
>         <mike at trausch.us <mailto:mike at trausch.us>> wrote:
>
>             On 6/17/2011 12:11 PM, Scott Castaline wrote:
>             > Sorry for replying to a reply, but to Mike, htop is
>             showing 16
>             > incidents of mysql, whereas top is only showing 1. Each
>             incident is
>             > using 1.0% of memory. I also noticed several incidents
>             of kworker*
>             > running of which (about 20) I don't remember the %Mem
>             for each.
>             You're probably seeing all of MySQL's threads in htop.
>             They together
>             will still be using only 1% of the memory...
>
>             kworker is a kernel thread, which has something to do with
>             ACPI.
>
>                 --- Mike
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Sorry I didn't get to thanking everyone for the input. I didn't have 
access to my system for about 3.5 days and my wife kicked me off of her 
work laptop. But thanks for all the feedback, I do have one more 
question for Greg in what is your feeling for Kingston, still a good 
product?