PaulCutcliffe Posted December 8, 2020 Share Posted December 8, 2020 (edited) I just bought 4 x DIMMs on eBay that were described like this: Corsair Vengeance 32GB (4 x 8 GB) DDR3 2400 MHz RAM in Red No Signs of any use or damage and work perfectly, very fast RAM! Please Note that 2 of the sticks have a carbon vinyl on the side as shown in the photos, which can be removed if necessary but can be hidden once inside a PC if put inbetween [sic] other sticks. When I received them, my PC wouldn't boot with them in unless I disabled XMP, and then CPU-Z said this about them: Slots #1 & #3: ============== Part No: CMY16GX3M2A1866C9 Timings Table: JEDEC #2 JEDEC #3 JEDEC #4 XMP-1864 Frequency: 457MHz 609MHz 666MHz 932MHz CAS# Latency: 6.0 8.0 9.0 9.0 RAS# to CAS#: 6 8 9 10 RAS# Precharge: 6 8 9 9 tRAS: 17 22 24 27 tRC: 23 30 33 36 Command Rate: 2T Voltage: 1.50V 1.50V 1.50V 1.500V Slots #2 & #4: ============== Part No: CMY16GX3M2A2400C11 <== 2400 vs 1866 Timings Table: & 11 vs 9 JEDEC #2 JEDEC #3 JEDEC #4 XMP-2400 <== 2400MHz vs 1866MHz Frequency: 457MHz 609MHz 666MHz 1200MHz <== 1200MHz vs 932MHz CAS# Latency: 6.0 8.0 9.0 11.0 <== 11.0 vs 9.0 RAS# to CAS#: 6 8 9 13 <== 13 vs 10 RAS# Precharge: 6 8 9 13 <== 13 vs 9 tRAS: 17 22 24 31 <== 31 vs 27 tRC: 23 30 33 44 <== 44 vs 36 Command Rate: 1T <== 1T vs 2T Voltage: 1.50V 1.50V 1.50V 1.650V <== 1.650V vs 1.500V I can see they are different specs or speeds, which, I suspect is why two are missing the spec stickers. :-( Anyway, in all fairness, I've requested a refund (I paid £140 GBP) and I've now received the return ticket so I guess that means he's accepting the return. Does anyone know whether this is why my system won't boot with XMP enabled? I had assumed that they would just all run at the slower 1866MHz rather than the faster 2400MHz of the other pair, but it seems that they don't work at all together unless on the default setting, which, I believe, is slower and makes my purchase a bit of a waste. Presumably, if I had 4 x CMY16GX3M2A2400C11 rather than 2 x CMY16GX3M2A2400C11 + 2 x CMY16GX3M2A1866C9 then they would all run happily together at the higher speed? One more thing: CPU-Z seems to be suggesting that the maximum bandwidth is currently 667MHz - is that correct, and would those speeds increase to 932MHz for the slower and 1200MHz for the faster modules, if only they were used on their own or with matching modules? Thanks to anyone who answers and sorry if my questions just prove that I don't know what I'm talking about - I'm a developer so this is way out of my field of expertise, but I just want the best performance I can get on a budget. Paul Edited December 8, 2020 by PaulCutcliffe Second image failed to post for some reason, so replaced with text. Link to comment Share on other sites More sharing options...
PaulCutcliffe Posted December 8, 2020 Author Share Posted December 8, 2020 (edited) Interestingly, I just tried Assetto Corsa's built-in benchmark with two configurations, and here are the results: With 32GB Corsair Pro Red but unmatched with XMP off Loading Time: 38 seconds Ave Frame Rate: 130FPS With 16GB Corsair Pro Red all matched with XMP on Loading Time: 130 seconds Ave Frame Rate: 146FPS So twice the RAM more than cuts the loading time in half, but having less but faster RAM definitely helps this game's frame rate, at least in this particular configuration.I guess if 16GB were less than the game required then those results would be different. And here are the different readings from CPU-Z: Part No: CMY16GX3M2A1866C9 Timings: DRAM Frequency: 666.3MHz FSB:DRAM: 1:5 CAS# Latency: 9.0 RAS# to CAS#: 9 clocks RAS# Precharge: 9 clocks tRAS: 24 clocks tRFC: 200 clocks Command Rate: 2T Part No: CMY16GX3M2A2400C11 Timings: DRAM Frequency: 1199.8MHz FSB:DRAM: 1:9 CAS# Latency: 11.0 RAS# to CAS#: 13 clocks RAS# Precharge: 13 clocks tRAS: 31 clocks tRFC: 361 clocks Command Rate: 2T Edited December 9, 2020 by PaulCutcliffe Link to comment Share on other sites More sharing options...
PaulCutcliffe Posted December 9, 2020 Author Share Posted December 9, 2020 I've just had a thought - if I were to swap the pairs around so the slower ones are in the primary slots then would I be able to get the 32GB to run at 932MHz, which, I think is the speed of the slower of the pairs?. Then I could see how that compares and whether I can get 32GB of the faster RAM for the same money before I sent it back. Link to comment Share on other sites More sharing options...
c-attack Posted December 9, 2020 Share Posted December 9, 2020 You can't run the XMP preset for a mixed kit. They have different preset values and the system can't reconcile that. It may or may not be possible to run them together, but you will need to manually set at least the primary timings. The place to start is the lower XMP values 1866 Mhz 9-10-9-27 for all 4. See if it boots up. It it works out OK, you can try 2400 11-13-13-31 @1.65v. It could work, but then the other kit was sold as 1866C9 for a reason. Frankly I would be looking to return. Not sure on the value as I don't track DDR3 prices anymore, but you did not buy a matched a 32GB 4x8 2400C11 kit. It could be a builder with a lot of kits and this was an accident, but people who wind up with mixed kits they can't get to work will dump them in this way all the time. Removal of the spec stickers suggests intent. Link to comment Share on other sites More sharing options...
PaulCutcliffe Posted December 12, 2020 Author Share Posted December 12, 2020 Thanks for your response. 😊 The guy held his hands up and claimed that he'd bought them around five or six years ago in two separate purchases and he'd simply forgotten that it was not matched, apparently. But no matter as he is happy for me to return it all. He was looking at accepting just the slower two but there's no way to do a part-refund on eBay so I'm sending it all back and either buying a matched set of four or possibly getting a new board and CPU with some DDR4 instead. Thanks again, and stay safe! 😷 Link to comment Share on other sites More sharing options...
DevBiker Posted December 12, 2020 Share Posted December 12, 2020 He was looking at accepting just the slower two but there's no way to do a part-refund on eBay That is absolutely, positively not true in the least. Not at all. Very muchly, bigly not true. Most decidedly not true. Fake News. Source: me. I sell on eBay. Quite a bit. Link to comment Share on other sites More sharing options...
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