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The RAM I have has an identity code 'pc3-10600u-999 hf' Upon searching for details I find only one result i.e. 'Ramaxel' DDR3. Alternatives such as Kingston or Corsair or Transcend does not show up.

Which may mean that a part of the number is manufacturer identity. I would like to replace a faulty RAM, but I would like to source from local market, perhaps a Kingston. I tried looking around for details and understood the part up to 'pc3-10600' i.e. it is DDR3-1333

Now the doubts I have are as follows:

  1. what is the difference between pc3-10600 and pc3-10666 ? Can I have both 10600 and 10666 on two channels of a motherboard?
  2. What does 'u-999 hf' part of 'pc3-10600u-999 hf' mean?
  3. What would be Kingston or Corsair equivalent for 'pc3-10600u-999 hf' ?
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If you want to know what type of RAM is compatible with your motherboard, you need to look up your motherboard (and CPU) spec sheets. – Bob Jun 27 '14 at 12:30
Perhaps my question wasn't accurate. Hence I detailed in description. A couple of years ago, RAM modules mentioned DDRX-XXXX. But, now I dont find that it any of the RAM modules I have here (Hynix, Ramaxel). I figured out that PC3 is indicative of DDR3. And the rest is clock speed. I had doubts which I have numbered above. @Jakke seems to have answered my queries rightly. – Anup Nair Jun 27 '14 at 14:46
correction: "And the rest is clock speed" --> "And the rest is data speed" – Anup Nair Jun 27 '14 at 14:58
up vote 3 down vote accepted

If you have any doubts which RAM will properly work in your system, you should visit the website They have a nice tool that tells you which RAM is compatible with your system (without any purchase obligation).

The main difference between pc3-10600 and pc3-10666 is the speed at which they work. You can combine the 2, but ALL your RAM will only work as fast as the slowest component.

The u-999 part of the naming is probably model number or so, nothing you should be worried about. The important part is the pc3-10600 or pc3-10666, which will indicate the type of RAM. DDR3 is usually noted as PC3-xxxx(x) and DDR2 is usually noted as PC2-xxxx. The xxxx indicates the performance of the DIMM, lower values are lower speeds. All brands use the same notation these days, so whether you go for Corsair, Kingston, Crucial or a white label, there won't be much of a difference.

Also, it doesn't matter all that much which brand you buy in terms of performance. There are very few companies in the world producing memory chips and they sell to all the major and minor vendors. The biggest difference between brands are the warranty, support and testing methods they use before shipping to the final customer. I always prefer a brand that offers lifetime warranty, but between all of them, I go for the cheapest one. That's just personal preference.

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For the sake of neutrality: It is likely that other manufacturers have similar services, I know Kingston does for example. :-) – TheUser1024 Jun 27 '14 at 14:20
@Jakke .. #3 in my question. From your answer, I should just leave the u-NNN part out and get a RAM matching PC3-10600, right? It is for HP desktop. I used Hynix from another machine (an assembled one) same PC3-10600 module. HP did not boot. But, the other machine boots. I am confused why that happened! – Anup Nair Jun 27 '14 at 14:53
Yeah that should work. Some vendors always try to lock you in and slightly modify parts so you can only buy from them. That's why I advised you to go have a look at crucial (or kingston, or other vendors' tools) to check compatibility before you buy. – Jakke Jun 27 '14 at 15:03
There is some incorrect information here. There is no technical difference between PC3-10600, PC3-10660, and PC3-10666. They all run at the same theoretical speed. The different numbers come from the fact that different marketers round off the speed at different spots, since the theoretical speed of all of those module types is (repeating) 10666.666... MB/s. Since it's repeating 6s, they have to cut off the repeating somewhere. (source 1) (source 2) Barring all of that, everything else is correct and agreeable. – ajp15243 Jun 27 '14 at 15:55

They have key notches in different places. Among the pins is a notch. Looking from the top side, the notch on the DDR2 lies slightly to the right of the middle point of the memory stick. On the DDR3, the notch is slightly to the left of the middle.

DDR: PC-1600 to PC-3200

DDR2: PC2-3200 to PC2-8500

DDR3: PC3-6400 to PC3-17000

And See this link Wikipedia diagrammatic representation

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Thanks. But needed details as mentioned in description. – Anup Nair Jun 27 '14 at 14:59

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