Why only 3 dimms

[Guest]

I have been working with motherboards and components for almost a decade now. I just had one question that seems rather odd.
Why do a lot of newer motherboards come with only 3 dimm slots?
That seems rather odd compared to most other things in computing. You would think 4 would make more sense.

 

[upec]

Because most people only need 3 dimm.

 

[Ncogneto]

Not really, there is a cost factor involved in the additional traces needed for another dimm socket. Add this to the fact that memory is available in much larger sizes, and seldom to people occupy more than three dimms it becomes an obvious choice for motherboard makers to trim costs on.

Another Cookie? Who is going to pay my dentist bill?

 

[tilepusher]

Hey W,
My version of the truth that I believe is, It is harder and much more costly to design a mobo that can fully utillize 4 slots, the first thing is the chipset has to be designed to handle it, and it just gets harder from there. This applys mostly to the newer(DDR) mobos.
Just what I have heard and believe.
Peace Out...........tile

WHAT????? I CAN'T HEAR YOU OVER THE ROAR OF MY CASE FANS! YOU'LL HAVE TO SCREAM!

 

[girish]

actually, there are a lot of high capacity DIMMs available now, and those are populated on both sides.

since the DIMM spec itself says the modules are actually two banks of memory on either side, the number of DIMM slots actually reduces to half of the number of banks the chipset supports. usually its 4~6 so 2~3 DIMM slots are natural.

Earlier, not many high capacity modules were available so you used muliplies of single sided low capacilty modules to make up larger memory that needed the slots in larger numbers. These days you simply get a single 512 MB DIMM or 2x256 MB DIMMs, combinations like 4x128 are extremely rare these days.

So why should the motherboard manufacturer spend more on the extra DIMM slot, the PCB space and development cost? He is too happy to give you a slightly cheaper board which you wont have any problem with it, especially the memory slots!

girish

<font color=red>No system is fool-proof. Fools are Ingenious!</font color=red>

 

[pvsurfer]

Very true and here's an actual case example. My friend recently built a new PC based on the Shuttle AK31A (one of the very few KT266A boards with 4 DIMM slots). After populating all 4 slots with Crucial 256MB Registered DIMMs (Shuttle stipulates Registered DIMMs if using more than 6 memory banks), he experienced booting and instability problems galore!

I should add that he is running everything at default settings (no overclocking), so 'pushing the envelope' was not the cause of the system's instability.

Removing the 4th DIMM brought about complete stability, but now he doesn't have the Gig of memory that he needs (for his photo-editing work). Since swapping DIMMs didn't reveal a bad memory module, he returned the 4 256MB DIMMs, replacing them with 2 512MB (Unbuffered) DIMMs, and is up and running without problems. Judging from his experience, and similar problems that I've read about, populating 8 memory banks on a KT266A board is a very difficult undertaking, and it's obvious that most mobo mfrs realize that!

<b>God bless the <font color=red>U</font color=red><font color=white>S</font color=white><font color=blue>A</font color=blue></b>

 

[labdog]

but a number of mb have PC133/PC2100 capabilities which need so about 5 slots


EasyInfo
I would like to Invest for my PC !!
ok, buy nothing.

 

[labdog]

but what's about the memory types compatibility ?



EasyInfo
I would like to Invest for my PC !!
ok, buy nothing.

 

[IntelConvert]

If you're asking if you can mix PC133 and PC2100 on a board that accomodates both types of SDRAM, the answer is no!

 

[labdog]

of course, not

i just want to say that if you haven't both types on the mb,

you can't eg use in first "old" PC133 you have with your new mb & upgrade after with new high perf DDR

so you can plan to by in first mb,
& a little later the new memory which can also be an quantity upgrade eg DDR 512M or 1G instead of PC133 64 or 128M

so you can manage your budget


EasyInfo
I would like to Invest for my PC !!
ok, buy nothing.

 

[tilepusher]

Hey Labdog,
My belief is that all mobo's that have PC133 and DDR slots, are budget mobo's so the are going to be cheap in nature by design. I would not buy a dual ram mobo, they also never perform as well as the normal mobo's, this includes the ECS mobo w/ the SiS 735 chipset..... it is outperformed by the Ledtech mobo with the same chipset. It is not the chipset that changes, just the goals of the mobo maker.........dual ram mobo's are for people on budgets, not over-clockers or high end users, they are going cheap so they don't need more ram slots than 2 each type. I think this is what you are asking about?
Peace Out.............tile

WHAT????? I CAN'T HEAR YOU OVER THE ROAR OF MY CASE FANS! YOU'LL HAVE TO SCREAM!

 

[girish]

Those 5 slots wont make any difference. you cant use both types of memories together so it reduces to either 3 168 pin SDRAM slots or 2 184 pin DDR slots! Still only 3 or 2!

girish

<font color=red>Nothing is fool-proof. Fools are Ingenious!</font color=red>

 

[labdog]

ok, right


EasyInfo
I would like to Invest for my PC !!
ok, buy nothing.

 

[Guest]

If you notice the new DDR 333 boards are coming out slowly. On the Abit and Asus models there is three slots but if your using DDR you can only use two of them. Wonder why they do that?

 

[tilepusher]

Hey N,
Did you see my first post in this string? It is not easy to develop Memory controllers/chipsets to handle Multi slots of DDR. Merry Christmas!
Peace Out...........tile

WHAT????? I CAN'T HEAR YOU OVER THE ROAR OF MY CASE FANS! YOU'LL HAVE TO SCREAM!

 

[girish]

as I said earlier, the chipset supports banks not modules, as each module can carry two banks, the number of slots are limited to half the number of banks it can support. motherboard makers provide more slots so that its easier to use low capacity single sided DIMMs in multiple numbers. but it has a limit because you could end up putting in more memory than the chipset supports.

that is, on a P4266 if you use a double sided DIMM (the one with chips soldered on both the sides) then you are left with only 2 banks but only two slots so you can only use single sided DIMMs in both or one double sided one in one of the slots. inthis case you just cannot use the third slot even if its vacant! this can be confusing nonetheless!!

girish

<font color=red>Nothing is fool-proof. Fools are Ingenious!</font color=red>