# RAM chip / module sizes (Why won't it fit?!)
**URL:** https://boards.straightdope.com/t/ram-chip-module-sizes-why-wont-it-fit/451694
**Category:** Factual Questions
**Created:** [June 3, 2008, 10:30pm UTC](https://boards.straightdope.com/t/ram-chip-module-sizes-why-wont-it-fit/451694 "2008-06-03T22:30:02Z")
**Posts on this page:** 9
**Page:** 1
### Author:  [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)
#### Post date: [June 3, 2008, 10:30pm UTC](https://boards.straightdope.com/t/ram-chip-module-sizes-why-wont-it-fit/451694/1 "2008-06-03T22:30:02Z")
As anyone who’s bought RAM for a computer knows, there’s a whole bunch of physical shapes to the stuff - SODIMM, DIMM, RIMM, and on and on.
Are there subsets to the “SODIMM” design? I bought some RAM for a laptop, and the package the module came in identified it as a 200-pin SODIMM. It doesn’t fit. The module’s overall width fits the laptop’s RAM socket perfectly, but the locator notch is off just enough to one side that I can’t get it in. “Just enough” being a noodge thicker than a business card - just enough that the hard plastic socket and the hard fiberglass module are unyielding and will not mate.
Do I have a wrong module or a wrongly-made module? I’ve never seen RAM modules have differences so slight that they might be overcome by forcing it in - normally these things just slip right in, and usually the modules’ sizes and locator notches are distinctly different that they can be identified at ten paces, as opposed to needing a micrometer.
The module in question is a Kingston “ValueRAM” - I thought Kingston made good stuff. Maybe a production robot was having a bad day?
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### Author:  [@FatBaldGuy](https://boards.straightdope.com/u/FatBaldGuy)
#### Post date: [June 3, 2008, 10:56pm UTC](https://boards.straightdope.com/t/ram-chip-module-sizes-why-wont-it-fit/451694/2 "2008-06-03T22:56:09Z")
Try turning it around and inserting it the other way.
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### Author:  [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)
#### Post date: [June 3, 2008, 11:22pm UTC](https://boards.straightdope.com/t/ram-chip-module-sizes-why-wont-it-fit/451694/3 "2008-06-03T23:22:58Z")
That would result in the locator slot being about an inch away, rather than half a millimeter away.
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### Author:  [@JSexton](https://boards.straightdope.com/u/JSexton)
#### Post date: [June 3, 2008, 11:38pm UTC](https://boards.straightdope.com/t/ram-chip-module-sizes-why-wont-it-fit/451694/4 "2008-06-03T23:38:07Z")
I’d go to [Crucial.com](http://Crucial.com) and put in your exact model of computer. It will tell you exactly what’s compatible and what’s not.
That said, this sounds more like a bad batch of RAM than a slight difference in model. Crucial will probably know for sure, though.
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### Author:  [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)
#### Post date: [June 3, 2008, 11:58pm UTC](https://boards.straightdope.com/t/ram-chip-module-sizes-why-wont-it-fit/451694/5 "2008-06-03T23:58:17Z")
Oh bother… I apparently flipped a digit or something. The laptop needs DDR RAM, but I bought a DDR2 module.
Still, I’d have thought the physical SODIMM package was universal.
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### Author:  [@Rysto](https://boards.straightdope.com/u/Rysto)
#### Post date: [June 4, 2008, 1:43am UTC](https://boards.straightdope.com/t/ram-chip-module-sizes-why-wont-it-fit/451694/6 "2008-06-04T01:43:13Z")
[QUOTE=gotpasswords]
Oh bother… I apparently flipped a digit or something. The laptop needs DDR RAM, but I bought a DDR2 module.
Still, I’d have thought the physical SODIMM package was universal.
[/QUOTE]
The physical incompatibility is probably intentional so that you don’t get confused as to why your memory isn’t working.
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### Author:  [@yoyodyne](https://boards.straightdope.com/u/yoyodyne)
#### Post date: [June 4, 2008, 2:47am UTC](https://boards.straightdope.com/t/ram-chip-module-sizes-why-wont-it-fit/451694/7 "2008-06-04T02:47:04Z")
[QUOTE=Rysto]
The physical incompatibility is probably intentional so that you don’t get confused as to why your memory isn’t working.
[/QUOTE]
It is.
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### Author:  [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)
#### Post date: [June 4, 2008, 3:26pm UTC](https://boards.straightdope.com/t/ram-chip-module-sizes-why-wont-it-fit/451694/8 "2008-06-04T15:26:16Z")
[QUOTE=Rysto]
The physical incompatibility is probably intentional so that you don’t get confused as to why your memory isn’t working.
[/QUOTE]
I researched SO-DIMM and DDR vs DDR2, and yes, the keys are off by a nearly microscopic distance between those two types. Just enough that they won’t fit, but close enough that you think “If I just push a little harder, it’ll go in!” Or, as I’ve seen people do with expansion cards - “If I just cut off this extra bit…” :eek:
If you ask me, it’s a noble intent with a stupid execution. If you want to make them different, make them _different_. Move the notch by an visibly different amount or even add a notch.
Oh well. Lesson learned, and the correct part is on order. At least it was only $35. Anybody want to buy a never-used 1 GB DDR2 module? 🙂
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### Author:  [@LurkMeister](https://boards.straightdope.com/u/LurkMeister)
#### Post date: [June 4, 2008, 5:04pm UTC](https://boards.straightdope.com/t/ram-chip-module-sizes-why-wont-it-fit/451694/9 "2008-06-04T17:04:23Z")
[QUOTE=gotpasswords]
I researched SO-DIMM and DDR vs DDR2, and yes, the keys are off by a nearly microscopic distance between those two types. Just enough that they won’t fit, but close enough that you think “If I just push a little harder, it’ll go in!” Or, as I’ve seen people do with expansion cards - “If I just cut off this extra bit…” :eek:
If you ask me, it’s a noble intent with a stupid execution. If you want to make them different, make them _different_. Move the notch by an visibly different amount or even add a notch.
Oh well. Lesson learned, and the correct part is on order. At least it was only $35. Anybody want to buy a never-used 1 GB DDR2 module? 🙂
[/QUOTE]
Actually…
I have a Gateway MX3228 laptop which uses DDR2 SODIMM, and I’ve been thinking of upgrading to 1GB RAM (which is why I’ve been following this thread). I don’t know if it makes any difference, but according to Gateway the memory speed on my current RAM is 533MHz and recommended their “low density” RAM (I have no idea what that means).