RAM curiosity, 800MHz vs 200MHz.
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| Author | Content |
|---|---|
| Bob_Robertson Oct 03, 2010 2:25 PM EDT |
Hi. When I bought this gnarly desktop last year, I made sure to pick fast RAM to go along with the 3GHz quad core Phenom2. Well, I was reading that "linux hardware commands" article, and tried "lshw": *-memory description: System Memory physical id: 12 slot: System board or motherboard size: 4GiB *-bank:0 description: DIMM Synchronous 800 MHz (1.2 ns) product: PartNum0 vendor: Manufacturer0 physical id: 0 serial: SerNum0 slot: DIMM0 size: 2GiB width: 18 bits clock: 800MHz (1.2ns) *-bank:1 description: DIMM Synchronous 200 MHz (5.0 ns) product: PartNum1 vendor: Manufacturer1 physical id: 1 serial: SerNum1 slot: DIMM1 size: 2GiB width: 64 bits clock: 200MHz (5.0ns) Now I _know_ there was only one setting for RAM speed in the BIOS setup. I'm going to go check that setting again after I post this just to make sure. So assuming I did set 800MHz, could this result be because of a fault in the RAM module? A fault in the BIOS? Suggestions welcome. |
| Bob_Robertson Oct 03, 2010 3:25 PM EDT |
Well, after the above I pulled both modules, compared them, they are identical DDR3-1600 modules. So I made sure to put them back in _opposite_ slots, just in case it is a hardware failure. No change, the result above is exactly the same as what I get now: *-bank:0 description: DIMM Synchronous 800 MHz (1.2 ns) product: PartNum0 vendor: Manufacturer0 physical id: 0 serial: SerNum0 slot: DIMM0 size: 2GiB width: 18 bits clock: 800MHz (1.2ns) *-bank:1 description: DIMM Synchronous 200 MHz (5.0 ns) product: PartNum1 vendor: Manufacturer1 physical id: 1 serial: SerNum1 slot: DIMM1 size: 2GiB width: 64 bits clock: 200MHz (5.0ns) I also checked a laptop here, it's got two banks of 512, both show as identical in terms of "width" and clock. Sanity check. |
| gus3 Oct 03, 2010 3:29 PM EDT |
Assuming the 18 bit bus is carrying 16 bits of actual data (maybe plus 2 parity bits), you're getting the same overall RAM speed from both modules: 1.6G/sec. I suggest a quick run of Memtest86+, just to see what speed it reports. |
| tmx Oct 03, 2010 3:38 PM EDT |
Try some other measurement softwares. Also your ram is rated at 1.6ghz, why are you running it at 800mhz, unless I'm not used to the new ram calculation system. Try to change some settings in the bios if it let you. Otherwise if you still have warranty I would just RMA the defective stick. |
| Bob_Robertson Oct 03, 2010 3:53 PM EDT |
Ok. Memtest86+ result: no failure, constant "speed" number of 9016MB/s M3A790GXH/128M if anyone is interested. Yes, Tmx, I was surprised too, but it seems that DDR3-1600 is to be set at 800MHz. If it were one stick or the other, shouldn't the numbers have reversed when I swapped stick locations? I'm going to ask in the ASRock forums to see if anyone knows what's up. Sadly ASRock "does not support Linux", so asking them will not work. |
| gus3 Oct 03, 2010 4:22 PM EDT |
I suspect it's a chipset matter, since it doesn't move when you swap sticks. If you don't notice Memtest86 tests running slower in higher addresses than in lower addresses, I wouldn't worry about it. Just under 9G/sec? Beats the pants off my desktop system. |
| Bob_Robertson Oct 03, 2010 5:01 PM EDT |
> Beats the pants off my desktop system. Well it did cost $700, about half again what I was expecting to spend. |
| caitlyn Oct 03, 2010 9:00 PM EDT |
I'm also surprised by the 800MHz setting. My oh-so-low-end eMachines EL-1300 (see: http://www.emachines.es/em/product.do?ctx1w.att21k=2&Languag... ) uses 800MHz RAM and reviewers assured me last year that it was full of outdated and limited tech. (Hey, for $159 new I'm happy.) P.S.: It seems Slackware and derivatives (SalixOS in my case) don't install lshw by default. I added it because, as you found out, it's pretty darned useful. |
| Bob_Robertson Oct 04, 2010 9:02 AM EDT |
> 800MHz Going into the BIOS several times yesterday (turning off the floppy controller, for example), the only way to get to "800MHz (1600)" was to go into the overclocking settings. So it may seem like not all that big a deal the way I'm writing it, but Hoy!, that motherboard seems to think it's a big deal since this is its top setting. http://www.asrock.com/mb/overview.asp?Model=M3A790GXH/128M One of the feature graphic buttons is "DDR3 1600(oc)" lshw was not installed automatically with Debian Squeeze, either |
| gus3 Oct 04, 2010 12:29 PM EDT |
I think I see the problem. The RAM slots have different colors! But seriously, that might be a visual clue, since the PCI slots are also color-coded. I found this on Tom's Hardware: http://www.tomshardware.com/forum/257592-30-what-ddr3-1600-d... The signal-noise ratio isn't very good, but the comment that stands out to me says the RAM needs to come from their Qualified Vendor List to be guaranteed full-speed in all 4 slots. Otherwise, the secondary pair will run slower. But, in your case, the actual RAM bandwidth comes out the same. So take my words with a truckload of road salt. |
| Bob_Robertson Oct 04, 2010 1:32 PM EDT |
Thanks, Gus, that's a great thread. The manual I got with the mobo didn't have a QVL, nor did it make any mention of a slot limitation. But those are things I'll keep in mind. Considering how much RAM remains unused on this system normally (only uses about 2G unless I do something silly), I don't see needing to use the other two memory slots any time soon. It would make an interesting experiment, though. Too bad I don't have two spare 2GB DDR3-1600 sticks sitting around unused... |
| Bob_Robertson Oct 04, 2010 1:35 PM EDT |
It just occurred to me to try using only one module, then running Memtest86+ to see if the number comes out any different, on the theory that maybe the second module is slowing things down... Oh Cromm, it's working, maybe I really aught not to be messing with it.... |
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