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Ram compatibility questions.

by hobbes / February 7, 2005 6:50 AM PST

If I have one shtick of ram that has a cas 2 rating and another that has a cas 3 rating, will they be compatible on the same system? Will the one ram have to slow down to match the other?

I've been trying to figure out the whole issue of memory density, quality, and its impact on compatibility. But my google searches have left me confused. My mobo's webpage was of no help and ram manufacturer's don't mention the issue at all.

Does anyone have a link that can help explain the whole issue of ram density and quality and its impact on compatibility? I understand that certain cpu's require higher grade ram else there is issues. But understanding what quantifies as higher quality and what to look for in the rams spec's to determine its quality is difficult.

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The motherboard...
by R. Proffitt Forum moderator / February 7, 2005 7:21 AM PST


1. If such works.
2. If one stick will slow down for the other.

There is no "grade" of RAM. They come in speeds and temperature ranges. However I have seen better circuit board artwork...

As to determining what it takes to interface such, unless you dive into electronics headlong, you may just have to read the motherboard guide to RAM or even use


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Please try harder
by hobbes / February 7, 2005 12:57 PM PST
In reply to: The motherboard...

"There is no "grade" of RAM. They come in speeds and temperature ranges."

From what I understand of it there is different grades or levels of quality for ram. Just no specific definition's, which was what my inquire about ram quality was all about.

I don't understand what your talking about when you say "temperature ranges". You mean how much heat a module produces? What does that have to do with quality?

"motherboard guide to RAM "
You mean my motherboard manual? You don't think I already tried that?!

"or even use"

Already tried that as well and it was only mildly more helpful then your post. Their support is specific to the memory they sell. Basically you put in your mobo model and they tell you which memory they sell that they guaranty to be compatible with that mobo. If it was crucial I was thinking of buying from I wouldn't need to ask about these issue here.

Lets start from the top, memory density.(not talking about size!)

Is it correct to say,
Low density memory is a 256mb module with 16 chips on it, a 128mb with 8 chips on it, or a 512mb with 32 chips on it and high density memory is half those chip numbers?

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Just me, the grizzled embedded electronics designer.
by R. Proffitt Forum moderator / February 7, 2005 2:08 PM PST
In reply to: Please try harder

Strange as it sounds, the memory chips are rolling off about a handful of fab lines in the world today with one chip looking very much like the other.

You must try harder since I won't given the vagueness of your inquiry. You may be searching for something specific. And you may burst into flames that I will not teach electronics or design here. I will help you find out if part B works in your board.


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And you could be a little more appreciative
by jeroethel / February 11, 2005 4:49 AM PST
In reply to: Please try harder

of the free suggestions you get in this forum. Mr. Profitt is a regular responder, not your employee.

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Get a grip man!
by racer42 / February 14, 2005 5:36 AM PST
In reply to: Please try harder

You didn't reveal you were talking about PC133 ram until your third post. If you are trying to buy that outdated stuff, save your money for a new mobo. No wonder nobody can tell what you are talking about. I do remember problems trying to mix various chip count DIMMs but that was like 1998 or something. Go scrounge a landfill or something so you can play around with combos to your hearts content. For God's sake don't BUY any of it.

The reason your mobo manual is no good is because it was only current on the day it left the factory. No manufacturer bothers to update that info. Email questions for products that are more than 2 years old have very little likelyhood of getting answered either.

And, just for the record: You come off like a beligerent @ss and I am surprised that Calvin will still hang out with you.

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Another thought...
by Willy / February 7, 2005 11:37 PM PST

Only an opinion here...

While there are various types of ram, excluding labels for now, the quality of ram is determined by now well it handles heat and its speed for stability. Once determined it sells it upon that rate. Once you stuff it into a system and fully use all slots, that "density" will determine the actual quality of the ram. If generic manufacturer expect possible problems if made within specs if of namebrand like Kingston, Crucial, or any other expect it to deliver. Cheaper ram fails usually because the testing wasn't done on a batch run, often enough or quality is just too hosey. More expensive ram tend to be tested often to keep quality up and reduce product failure rates. What ram can't sustain a certain speed level maybe offered for lower speed level if stable, to keep product rejects to a minmium, but once the user tweeks it on a system to a higher level it fails then or later, thus you find here and elsewhere that help forums, suggest you return to stable or default levels rated for your ram. Alot of this is "auto setting" for ram but some tweaks can be made, but those only are accepted if the ram can handle it, if not expect a locked system or rejection. Plus, for CAS rating, most is auto setting, but if you can change it, and the CAS rating differ from one ram to the other, the slower rating is best for operation, flaky operation otherwise. On top of all this, keeping ram from the same vendor/maker helps here as differences while not apparent may become so as touchy or intermit problems crop up for no apparent reason. For ram density, if you refer to how much is on a stick, like 128mb vs. 256mb, then a good rule of thumb is higher ram first then the next higest. If the support website offers a "ram map", may provide how ram can be installed to reach levels of supported ram install at one time. Example: a mtrbd. supports atotal of 3gb of ram, you have 2gbs of ram as 1gb, 2-512mb of ram sticks. The map shows you install the 1gb in slot 1, the 2-512mb in slot 2 and slot 3. -OR- may show that the 2-512mb be in slot 1&2, then 1gb in slot 3. Some support websites don't always offer a ram map as this is was more helpful during the PC66 and PC100 days, PC2700, etc, it may not be provided, but look anyways.
I hope this helps...

enjoy Happy -----Willy

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Ram density
by hobbes / February 9, 2005 4:49 PM PST
In reply to: Another thought...

"For ram density, if you refer to how much is on a stick, like 128mb vs. 256mb"

*sigh* I specified I was not talking about size.
PLEASE don't make me repeat myself over and over, trying to get as detailed as possible within consideration of asking for technical information I don't have (I mean if you don't understand something its hard to get into the details of it) Yet still not hear what I'm saying.

@proffitt I never asked for you to "teach electronics or design"

Anyways, from inquires elsewhere I have patched together a primitive understanding of the ram density issue. Apparently its all about how much memory is squeezed into the individual chips on a particular piece of module(ram). As time goes on they squeeze more onto the individual chips but I guess older motherboards are unable to use said denser ram. (even though the ram is the right size for the mobo[since it has nothing to do with size!]) Which can cause your mobo to only see half of your ram or worse.

I'm not sure if ram density is more standard (8 chips on a 256mb ram being high density, 16 chips ona 256mb ram being low density?) Or whether ram being "high" or "low" density changes in respect to general increases in ram compactity relative to older motherboards ability to see said level of compactness. Or what level of compactness of ram is compatable with my specific mobo.

One tech person suggested ram density incompatibility issue only applies if you want your ram to clock down (like a 133 on a 100 board) which seems to contradict the admittedly limited information I found elsewhere.

Fine, could you tell me if the 64 MB SDRAM PC133 168 PIN Hyundai - HYM7V63801 I recently bought off of ebay would work on my gigabyte brand ga-7IXE mobo? Whether its too dense/low grade or not? Especially tricky and confusing since is there homepage, apparently (are they hynix or hyundai, how confusing) and have no listing of that model of ram (and never bothered to reply to my email)

Or could you tell me if said ram would have any incompatibility issues with my current pc133 256mb stick of kingmax tiny bga -MPGB63S-68KI3 with a CL of 2?

How about a PC 133 256mb micron MT16LSDT3264AG? Might that be incompatible with any of the above mentioned?

Do you need majorbrand grade memory or higher to not have issues with a athlon CPU's high bus speed like many memory seller sites have said? What quantifies as "major brand"? I know there are issues with the quality of the material used (like whether its 4 or six layer, gold contacts or not, quality of the board itself etc) and general design (like whether it uses bga or tsop etc)

But absorbing and quantifying such issues and then applying it to a intelligent ram purchase is a major headache, please help.

I do hope I was detailed enough in this post.

Whats that you say? There is no such things as grades of ram you say? Tell that to memory selling sites such as or any other countless number of memory specialists

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Looks OK.
by R. Proffitt Forum moderator / February 9, 2005 8:51 PM PST
In reply to: Ram density gives us enough clues that a PC133 64MB stick should work in your board.

I will not supply the link to the Gigabyte manual, but a 64MB was noted there. And should be fine with the 256MB stick noted.

I'm here to converse with you about such things. And if you want to take out some ire then I suggest you do so with the purveyors of the products. If they won't answer such a question then why are you dealing with them.

You also have to ask a small enough question or risk me (and others) trying to find the real question. The area you started off with could take months to convey all the needed info, but narrowing it down to could this work with that makes it possible to find an answer.

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WHY do you think they are compatible?
by hobbes / February 10, 2005 4:02 AM PST
In reply to: Looks OK.

<i>I will not supply the link to the Gigabyte manual, but a 64MB was noted there. And should be fine with the 256MB stick noted.</i>

As I already clearly said in previous posts, I already read the mobo manual long before posting. As far as "a 64mb" being mentioned there, I seriously doubt that specific stick was mentioned in the manual. If it said it takes 64mb sticks in general, what does that have to do with anything? That doesn't tell me if its compatible with this specific stick. Or whether this specific stick is compatible with my existing ram.

Why is it that you believe the 256mb stick I mentioned would be compatible with my mobo or existing ram?

As far as my "ire", I'm sorry. See, you started off telling be the obvious- the motherboard determines ram compatibility. Then you tell me I'm full of it when I speak of ram grade. Then you suggest that I consult my mobo or in such a way as though the possibility of me having already tried both of those didn't strike you as even remotely possible.

Anyways, directly contradicts your statement of 'no such thing as ram grade'.

So I am sorry I got irritated when you were trying to help. It doesn't help my "ire" though when you say silly sarcastic things like "I will not supply the link to the Gigabyte manual" especially when I've already clealy stated that I've read the mobo manual.

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Try it.
by R. Proffitt Forum moderator / February 10, 2005 5:00 AM PST

The timing looked good (CAS and PC133) and the manuals, while not listing this exact part noted the 64MB size.

If you feel you want someone to do tech support that you can make demands, then pay for it. I'm free and friendly and give you the best advice I can with what experience I have as an embedded systems designer. Some want links, quotes, me to come over and do the actual work and warrant it, but this will never happen.

There again are speeds and commercial, industrial grades of RAM but for consumer PCs and your board if we hit the speed, timing there is no grade. If you want to pay for a better grade, then do so. Waste of money.


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by Willy / February 9, 2005 9:55 PM PST
In reply to: Ram density

Your "density" issue if I take it right refers to side-oned or two-sided populated ram sticks. Even, if all one-sided, where all the ram is on one side, the CAS involved is nothing more than "timing". If the timing becomes lost or irregular it'll(system) place wait states to generate overall sync with the system, to include all populated ram slots. One reason to keep any ram sticks from one vender/maker to decrease such issues, keep in a frameset where incompatibility is less to be an problem. I give practical advice rather than any theory or such as that gets into areas I have no need to be in. Yeah, it gets confusing, but don't dwell too much into it, the rewards are slim. Silly

When you buy "namebrand" componets they tend to be uniform in specs and can be counted on to deliver within those. However, alot still depends on the mtrbd. chipset and/or readiness to be stable. I believe in my previous post, I mentioned, two types of ram, generic and namebrand, let me further expand that to include "premium" as well. Premium, being the upmost any vendor can uphold to certain specs and lashingly says so. Namebrand, implies any vendor that is happy to place thier name to thier product, other than ?XYZ123? Ram Co. that pushes out ram product and just calls it a 128mb stick, etc.. If I didn't fully answer your question, I'll quit and leave it to others. Sad I just hope it helps more than hinders your quest.

good luck Happy -----Willy

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Not exactly
by hobbes / February 10, 2005 4:09 AM PST
In reply to: Well...

"Your "density" issue if I take it right refers to side-oned or two-sided populated ram sticks. "

Well from my limited understanding of the issue of memory density. Its about the number of chips on a module or possibly the amount of data on each chip, not whether they are on one side or both sides. (obviously though if there is alot of chips they are more likely to put it on the other side for simple lack of room, though not a direct indication of ram density)

And the CL issue is altogether completely separate from the ram density issue.

Does someone have a resource link they could drop me that details the issue of ram density?

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Look here maybe...
by Willy / February 10, 2005 1:09 PM PST
In reply to: Not exactly
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Double-density may be cheaper even if it only half works
by Cedders / March 9, 2005 7:18 PM PST
In reply to: Ram density

Thanks. hobbes, that was useful. Unfortunately after the event for me.

Having spoken to Crucial, you can reliably tell the density from the part number. If it is CTxMyS4Dz then it's single density (e.g. 8 chips for 128MB). If it's CTxMyS8Dz, then it's double density (e.g. 4 chips for 128MB), and you may well only see half the RAM on older chipsets (say 750Mhz or LX).

I think of the '4D/8D' number as being the number of bytes wide the data bus is, so older motherboards only see at most 4D. Messing with timings or order of modules won't help. (I'm guessing here, but it's probably roughly right.) Incidentally, when you see xMy that's usually number of megabitz per row times width, so 16M32 is 16Mbit x 32 bit wide = 64MB on the chip/module. The z is the response speed in nanoseconds, so z=10 will probably be PC66.

I don't think there's any equivalent way of telling from Kingston's part number, except the price. Interestingly, 64MB of S4 PC133 from Crucial is more expensive (

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A couple o' things...
by Robert / February 11, 2005 1:16 AM PST
In reply to: Try these links...

To those trying to help:

Man you guys are nice...just trying to figure out why, after the first diatribe, anyone wants to help out at all...

To the person who posted originally:

Why don't you just buy RAM that you know is compatible with your MoBo & call it a day already? RAM is pretty cheap these days, Did you try to use them together? Did they work? Was the PC speed ok? Answer these questions & you'll have the answer...I'm not sure I even know what the question was at this point...

Play Ball!!!

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backward compatibility
by dsholden / September 20, 2007 7:32 AM PDT
In reply to: A couple o' things...

I inherited a Compaq Presario with a bad 256Mb PC2700 333Mhz memory card. An upgrade/replacement 512Mb PC2700 333Mhz will cost $20.99. However, I noticed that newer memory is cheaper, i.e. 512Mb PC2-5300 667Mhz is only $14.99. Is the newer RAM backward compatible and does PC2-5300 fit in the same memory slot as PC2700? My theory is that I can spend less for equal performance now, and possibly use the memory on a faster mobo later.

Thanks for the help,

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Here is a link for memory types....
by Jwd1savh / February 11, 2005 5:51 AM PST

This link will tell you the type of memory best suited for your motherboard, of course they try to sell you there memory, but it still gives you info. on the type needed.

Remember you will need to know the manufacture and model of your motherboard.

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by puicac / January 3, 2008 8:32 AM PST

Memory Density CAN NOT be used as criteria why would work or not a memory or to determine the actual quality of the RAM!

"Hi Density" versus "Low Density" is just some arbitrary slang for "I have a fake from an unknown memory non-working problem" just add to the confusion as explain further:
There is no accepted industry definition of "high density" relative to standard or low
density ? is amateurish and an arbitrary terms to try justifying more a non-working fake!

For Example: SDRAM Density is 1 Gbit for each element memory stick is a valid statement.

However a statement as: ?SDRAM Density is 1 Gbit for each element memory stick? is a valid statement.
See officially at Intel that Density definition as is expressed in numbers of Mbit or Gbit, in this case should be 1 Gbit , don?t full around thinking the uninformed people will buy your fake Samsung, se for example at Intel how officially ?Density? is defined (SDRAM Density is 1 Gbit and is not changed and can not be used as criteria):

See the last two explanations from this forum (scroll to the bottom):


Also here we found out why the RAM Density of 1 Gbit (For example) and is not changed and CAN NOT be used as criteria why would work or not or to determine the actual quality of the RAM:

Density is the capacity or size of a DIMM module or the capacity or size of each DRAM unit on a DIMM or RIMM. Density is normally referred to in megabits (Mb) when referring to DRAM units and in megabytes (MB) when referring to an entire DIMM module (see it at):

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