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Random Crashes

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Oct. 29th, 2006 | 10:51 pm

Over the past month or two my mac book pro has been suffering from random crashes. Most frequently when running second life, followed by WoW, followed by no pattern I could discern. It'd gotten bad enough that leaving SL running for a few tens of minutes would cause the system to reboot.

However when I pulled out the second 1GB non-apple stick of memory it seemed to run more reliably (though slower).

So today I went to frys and bought two 1 GB sticks of DDR2 memory. I was even a bit obnoxious at the register, when I looked at the two SO-DIMMs I noticed that the formatting for the serial number for the sticks were different, and I asked them to get me two that were more similar. (E.g. one was something like XXXX XXXXX and the other was XXXX-0-XXXXX, and in a different font).

Shockingly they complied and they sold me two sticks where the model number and one set of the two mysterious small fonted numbers matched.)

I hope that my guess that having DDR2 ram from two different vendors was the source of my systems instability.

At least while I was worried that the logic board was going, I backed my home directory up.
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Comments {17}

Jeffrey

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from: jeffrey
date: Oct. 30th, 2006 03:16 pm (UTC)
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This is fascinating. Why does a greater difference in serial numbers matter?

Actually, I often have RAM issues. I mean, well, we bought ram for my PC a couple years ago and due to the person in the eBay auction being somewhat shady and us not knowing what we were doing all that well, I ended up getting the wrong kind... I can't even remember what was wrong about it now.

They fit and everything, but I had to find help online on how to get them to work and it turns out I had to install a much older Bios for some reason in order to get my computer to recognize the ram.

I bet that might make a lot more sense to you than it does to me. :/

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Diane Trout

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from: alienghic
date: Oct. 30th, 2006 05:39 pm (UTC)
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I think part of the problem was I confused DDR2 with Dual Channel.

I think DDR2 can transfer data on both the start and end edge of the computer clock pulse.

Dual channel ram speeds things up by spreading memory access between the two banks of memory. In dual channel for the range of memory address between 1 and 1000, all the odd numbers will be in one bank, and all the even will be in the other. This helps speed things as theres a certain recovery rate before memory is ready to be re-read.

The lore is that the more similar your memory is the less likely the slight differences in how the memory responds is going to confused the computer and cause it to crash. This is especially true in the case of dual channel memory as the computer has to pull from both memory banks all the time.

The reason I sent it back and asked for two with the similar serial numbers is the closer the numbers were the more likely it was that the two sets were made at the same plant with the same components. In a factory small production details drift over time and things made on different days or even between the beginning and end of a production run may differ in subtle ways.

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Diane Trout

(no subject)

from: alienghic
date: Oct. 30th, 2006 05:40 pm (UTC)
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Perhaps you got slower speed memory that they stopped supporting in the newer bios?

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no, YOUR mom

(no subject)

from: theinfamousmom
date: Oct. 30th, 2006 06:43 pm (UTC)
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Of course, now you have access to on-site Fry's-shopping consultants so you won't make that mistake again. :)

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Jeffrey

(no subject)

from: jeffrey
date: Oct. 30th, 2006 06:51 pm (UTC)
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I can't buy RAM in a store. I would never be able to figure out what I needed.

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no, YOUR mom

(no subject)

from: theinfamousmom
date: Oct. 30th, 2006 07:34 pm (UTC)
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See "on-site Fry's-shopping consultants," above.

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Aluta Corinthiaca Sumptuosa

(no subject)

from: dragonblink
date: Oct. 30th, 2006 07:38 pm (UTC)
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Fo realz, yo. I never go RAM shopping without my handy A+ certified technician or my professional sysadmin girlfriend.

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Jeffrey

(no subject)

from: jeffrey
date: Oct. 30th, 2006 08:01 pm (UTC)
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But if they don't know the exact specifics of your computer, how could they possibly know what you need either?

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Diane Trout

(no subject)

from: alienghic
date: Oct. 30th, 2006 08:21 pm (UTC)
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That's why I'm fond of opening the computer up first and looking at the system board. When the engineers do something thats seriously incompatable they'll usually change the connectors so you can't accidentally plug the wrong thing in.

Though as you found out with you're ram story, you still might need to check what component speeds that particular system supports.

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no, YOUR mom

(no subject)

from: theinfamousmom
date: Oct. 30th, 2006 08:27 pm (UTC)
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AAAAAAAAAAAAAAARGGGHHH!!! How do you know the exact specifics of your computer? You RTFM and then you tell the person who's selling you the memory what you want!

Grumble grumble Fry's customer grumble grumble.....

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Diane Trout

(no subject)

from: alienghic
date: Oct. 30th, 2006 08:48 pm (UTC)
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Wait now I remember how this is supposed to work.

The sucker client purchases a support contract where the computer and its upgrades are all handled via the company. Thus the client need know nothing about computers and the company gets to keep its lucrative support contract.

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Jeffrey

(no subject)

from: jeffrey
date: Oct. 30th, 2006 09:47 pm (UTC)
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Well my computer doesn't really have a manual, but I digress. My point is I have never ever found any salesperson in any retail outlet who had even the smallest clue, and I'm not fond of going back to stores over and over and over again just to get the right thing. So I'd probably do like we did last time and just get it over the internet or something.

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Diane Trout

(no subject)

from: alienghic
date: Oct. 30th, 2006 10:43 pm (UTC)
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Some of the technicians at the burbank pc club have a clue. (Or at least they did about 6 months ago, its hard to say if the gamers are still there or not).

I also think that there's a wealth of computer experience available from people you live close to now.

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Jeffrey

(no subject)

from: jeffrey
date: Oct. 30th, 2006 10:58 pm (UTC)
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Yes, that last part is really very nice. :)

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no, YOUR mom

(no subject)

from: theinfamousmom
date: Oct. 30th, 2006 11:08 pm (UTC)
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Chee, I am having the worst time getting this posted! Memory I know about, posting on LJ I don't!

Take it from the person who worked at Fry's for three years: The salespeople are not going to have a reference book with the kind of memory each and every computer out there requires (mainly because compiling such a thing would be physically impossible). It's up to the customer to find where in the computer's documentation (whatever that may be) it says what kind of memory the computer requires, write that down, take the paper with the writing on it to the store and tell the salesperson that's what you want.

You also tell them that you don't want the cheap-ass stuff that's only good till you take it out of the package, you want the kind with the lifetime warranty. Even the dumbest ring-tailed lemur in the cage at Fry's can handle a specific request like that.

But even so, when you go to the cash register and they bring you the box with the memory in it, check the sticker on the outside to make sure it's what you asked for a-la alienghic's message, above.

Or you just tell the whole Inf crew you're going to Fry's and ask us if we want to go along, and we will ask you to write down what kind of memory your computer needs and we will do battle with the cage monkeys on your behalf.

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Jeffrey

(no subject)

from: jeffrey
date: Oct. 30th, 2006 11:25 pm (UTC)
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I got four copies of that post in my email.

Anyway, it's not like I'm going to have the money to get more Ram or a new, big shiny hard drive anytime soon anyway. I was merely speaking from past experience.

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no, YOUR mom

(no subject)

from: theinfamousmom
date: Oct. 31st, 2006 04:35 am (UTC)
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Yeah, I know, for some reason I messed it up repeatedly when I tried to post it. Some days you're the windshield, some days you're the bug. :)

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