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SDRAM divided by 4

Posted on 2001-08-04
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Last Modified: 2013-11-10
My brother has an old motherboard with a 66 MHz bus. The motherboard has 1 DIMM and 4 SIMM slots. The manual states that the DIMM can hold max. 128MB.

When we put a SDRAM DIMM module in the DIMM-slot each time the motherboard only detects the capacity of the memory module divided by 4. We've tried the following:
256MB SDRAM 133 MHz -> 64 MB detected
128MB SDRAM 133 MHz -> 32 MB detected
128MB SDRAM 66 MHz -> 32 MB detected

Is there anyone who can explain why only a quarter of the capacity of the chips is detected. The frequency of the memory module doesn't seem to solve the problem.
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Question by:detempel
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Expert Comment

by:jhance
ID: 6351376
Note that these "combo" motherboard usually share the DIMM socket nearest the SIMM sockets with the SIMM sockets.  

So they CANNOT have memory in both the SIMM sockets and the DIMM nearest the SIMMs.  You didn't specify that you were doing this but it's a common problem.
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Author Comment

by:detempel
ID: 6351390
The manual states that DIMM and SIMM can be used at the same time. Originally it contained 32 MB SIMM and 32 MB DIMM and detected 64 MB. So that's no problem.

The problem occurs when the SIMM-sockets are empty and ONLY the DIMM socket contains SDRAM.
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Expert Comment

by:jhance
ID: 6351537
Please read the manual more closely.  

The SIMMs and DIMMs CAN be used at the same time but I think you'll find that it says that NOT ALL the SIMM and DIMM sockets can be populated at one time.  It may not explicitly state that but it usually is stated by the omission of that configuration as a possibility.

The most common motherboard designs treat the 4 SIMMs and the one DIMM socket as common.  So it's one or the other for that "pair" of sockets.
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RoadWarrior earned 200 total points
ID: 6351552
Sounds like an Intel 430 VX  chipset motherboard that only supports DRAM device densities of 16Mbit, these old boards need a special configuration of chips on the DIMM to work right, 64Mb modules in this arrangement are very rare, 128Mb modules in this arrangement, well, I've only ever heard of them from the motherboard manufacturers. Those chipsets are best left with 32Mb DIMMs on account of it's all you can rely on to work well with them.

regards,

Road Warrior

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Expert Comment

by:pbessman
ID: 6351614
I think it is a total of 128 not, 128 in each bank.  IF you have four DIMM slots this is probably the case.  How many DIMM slots do you have?  4x32=128
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by:pbessman
ID: 6351621
I have seen where you either need a jumper setting to switch from SIMMS to DIMMS 3.3 or 5.5 volts or a BIOS mention to enabled the sockets.  (Been a while)
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Author Comment

by:detempel
ID: 6351627
The motherboard has 4 SIMM-slots and 1 DIMM-slot. The manual states that the maximum capacity of a chip is 128 MB.
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Author Comment

by:detempel
ID: 6351637
No jumpers or enabling sockets is required. The manual explicitly  states that there are no jumpers necessary.
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Author Comment

by:detempel
ID: 6351665
Hi RoadWarrior,

The memory we bought has these specs: 128MB DIMM (16Mx64 DIMM /8Mx8). How do I know if this module uses 16Mbit density chips?

If I understand what you're saying 16 chips of 16 Mbit will lead to 16 * 16 Mbit = 16 * 2 MByte = 32 MByte.

Regards,
Erik Tempel.
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by:pbessman
ID: 6351691
OK put in 128 DIMM, reset the BIOS jumper and see what happens.  It should detect your RAM.


"The manual explicitly  states"???  Please enlighten us with the details about this board.  Please share with us the brand and model of this motherboard.

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Expert Comment

by:Don Thomson
ID: 6351695
Some of the older MB are picky about the TYPE of DIMM they can use. Some wan't straight non-parity - some want parity, some EDO  - some fastpage. Does your manual give any specs.
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Author Comment

by:detempel
ID: 6351710
Type: W-P55VT2
Manufacturer: Winco
Site: www.winco.com.tw (no longer accessible)

Quotes from the manual:
"Supports up to 256MB RAM in three banks using 72 pin SIMM modules of 1,2,3,4,8,16,32,64 or 128 MB with support for EDO, BEDO or Fast Page Mode memory and 168 pin SDRAM configuration."

"The W-P55VT2 supports three memory banks and provides four 72-pins SIMM and one 168-pins DIMM sites for memory expansion. The sockets support 1M x 32 (4MB), 2M x 32 (8MB), 4M x 32 (16MB) and 8M * 32 (32MB) single-sided or double-sided memory modules. The memory timing requires 70 ns Fast Page devices or 60 ns EDO, BEDO or Synchronous DRAM. Memory parity generation and checking is not supported (DRAM modules may be parity [x36] or non-parity[x32])."

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Expert Comment

by:pbessman
ID: 6351850
And just what does it say about the DIMM SLOT???
What are you using PC100 or PC133?  Perhaps you should see if you can get some older PC66 memory as that may solve your dilemma.

I found this memory upgrade available and cheapest for your system.  128MB EDO or Fast Page 60ns Buffered 16x64. 5v 168 pin (major brand Compatibility guaranteed - Major Mfgrs $ 49
http://www.coastmemory.com/


BTW, I went to google and searched using "W-P55VT2".  It returns a lot of results, 3 pages.  Most of which are memory sales outlets offering "32MB SDRAM of modules".
Perhaps you would have better luck using the 32MB Simms over the 128MB DIMM.  Perhaps there is a small computer store near you that offers used RAM at a discount.  
Where I live I can get them but they are approximately $1 per MB.  
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Author Comment

by:detempel
ID: 6351869
No extra information on the DIMM-slot is given. Tried PC66 memory of 128 MB and the motherboard reported 32 MB.

If I remember well 256 MB was reported as 64 MB. So that would be cheaper than buying SIMMS. Gonna retry that to be sure.

Anyway was mostly interested in an explanation and not practical solutions.

I'm pondering over the 16 Mbit and 64 Mbit chips.
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by:SysExpert
ID: 6351930
<< I'm pondering over the 16 Mbit and 64 Mbit chips.

The problem stems from the fact that newer chips are made with higher densities, and the older chips are no longer manufactured. Your motherboard apparently does not support the higher density chips.

Just my 2 cents...

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Expert Comment

by:magarity
ID: 6351989
My system also has a combination of SDRAM and EDO slots, and while my manual also says you *can* use them together, it goes on to say that this is not a good idea and that wierd things are likely to happen.  I've never tried it, and recommend you don't mix types either.

It doesn't though, mention anything about sharing the slots as jhance suggests (but it's not a one SDRAM system; there are 4 of those with 8 EDOs), I have to wonder where he saw a motherboard that did that...
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Author Comment

by:detempel
ID: 6352032
How can I see if a module has low density chips (16Mbit) or high density chips (64Mbit) and are there memory chips with a different density.

One of my chips reads "VT28SD16M8PC-7". How do I know the manufacturer and how do I find a datasheet. It's a chip of 128 MB PC133. That's detected as 32 MB.
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by:SysExpert
ID: 6352041
You can normally tell by the amount of IC chips actially on the DIMM. The fewer it has, the higher the density.
128 MB low density should have at least 16 chips ( 8 on each side ).

Less than that means higer density.

How many does yours have ?

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Author Comment

by:detempel
ID: 6352111
It has chips on one side not sure of the amount should be 8 I think. Have given it away to my parents. Guess it have been high density chips.

Still wanna know how I can tell who's the manufacterer. I have a program that can read the eprom. But the data of the manufacterer is not entered in the eprom.
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Expert Comment

by:RoadWarrior
ID: 6352162
If the manufacturer wanted to be identified, they'd put their name on it. Kingston, Micron, Crucial Viking etc, are proud of their product.

The low density SysExpert mentioned would be 64Mbit, which is low density for PII class motherboards etc, 440BX chipsets etc favour these. For an older P1 class system, we'd be looking for a lower order of density again. 128mb in 16Mbit devices would need 64 chips, the darn thing would probably be a few inches tall too.

The chip you had on your DIMM there, "VT28SD16M8PC-7" sounds like 16Mbit x 8bits wide = 128Mbit, 8 of them per DIMM.
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Author Comment

by:detempel
ID: 6352262
If a module with 8 chips is detected as 32 MB doesn't that mean that each chip 'holds' 4 MB or 32Mbit of data ?

That explains why the module from 256 MB with 8 chips on both sides is reported as 64 MB. Because 16 * 32 Mbit = 64 MB.

If this is right it means my motherboard can recognize chips up to 32 Mbit.

Or am I talking nonsense here.
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Expert Comment

by:RoadWarrior
ID: 6352578
Yeah, that makes sense, that's what I figured too, but it's strange somehow. I don't recall any chipsets being limited to 32Mbit, It might recognise 32Mbit DRAMs but give errors in actual use. Hmmmm.
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Expert Comment

by:SysExpert
ID: 6352689
Like I said, your motherboard only recognizes the lower density chips, it wraps around on the higher density ones and this can cause problems.

You need to find 32 Mbit chips max, so look for a 128 MB DIMM with 32 chips or 64 MB DIMM with 16 chips.


I hope this helps !
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Author Comment

by:detempel
ID: 6352985
I have some more information. The datasheet of the chipset can be found at this address: http://www6.tomshardware.com/mainboard/96q3/960710/

Regarding this datasheet I'm led to believe the maximum capacity of a DIMM-module is 128MB (128MB*4=512MB).

I'm thinking of trying the 256 MB module again next thursday when I'm at my brother's place. Wanne be sure it reports 64 MB. Since on the site of Kingston 32Mbit chip density isn't mentioned: http://www.kingston.com/tools/umg/newumg04.asp

Next the BIOS. Is it possible the BIOS affects the maximum density of the chip recognized. That is if the chipset recognizes chips of density 64Mbit can the BIOS restrict that to 16Mbit.

Some time ago I 'killed' my BIOS and revived it with a 'hotswap' using an evaluation-BIOS I accidentally found on the Internet.
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Expert Comment

by:RoadWarrior
ID: 6353052
What seems to be happening is that you board is only seeing 4Mbit deep into the DIMM, the specs you just posted say the board can handle 4 banks, so what I would recommend as the most likely 128Mb DIMM to work would be one with 64Mbit DRAMs, arranged as 4Mbitx16bit, making 4 banks of 32 Mbyte, 16 chips per DIMM. I think if you can get one of those it will work.

regards,

Road Warrior
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Author Comment

by:detempel
ID: 6355051
Why do you conclude my board is only seeing 4Mbit deep?

I have one DIMM-socket. This DIMM-socket is called a bank in my motherboard manual. But if I read the SPD e-prom using the program 'ctspd.exe' it says the SDRAM consists of 4 banks. I'm led to believe that the term bank leads to confusion. Can you tell me what's the difference between the bank my motherboard manual mentions and the banks inside a SDRAM-chip.

You state 'making 4 banks of 32 Mbyte' what do you mean by this. What I understand is it's 16 chips of 8MByte each.

Also I've read chips can be stacked inside a housing. So one housing can contain two chips. For instance 16 housings can contain 32 chips with a density of 64 Mbit.

The info on my chipset on http://www6.tomshardware.com/mainboard/96q3/960710/ leads me to believe my board accepts 16Mbit density chips max.

My theory about the 256 MB module reported as 64 MB is as follows:
- the module contains 16 housings;
- each housing contains two 64Mbit chips;
- my motherboard only recognizes 16Mbit of each chip;

Thus the capacity with 64 Mbit: 16 * 2 * 64 Mbit = 256 MB
and the capacity with 16 Mbit : 16 * 2 * 16 Mbit = 64 MB

Does this make sense ?

Also pondering about a way to get to know what's the density of the chips on a memory module. When I read the SPD on the memory modules I bought, the data of the manufacturer isn't entered. Maybe info about the density of the chips can be found somewhere in the SPD eprom.
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Expert Comment

by:SysExpert
ID: 6355839
I would look for a newer BIOS, It may help.

BIOS
http://www.ping.be/bios/numbersami.shtml
http://www.motherboards.org/ubb/Forum2/HTML/
or check the motherboard manufacturers website.
To ID it go to http://www.sysopt.com/mboard.html

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by:RoadWarrior
ID: 6359983
Often a motherboard manual will refer to a bank and mean 64bits worth of modules, i.e. one DIMM slot or 2 SIMM slots. However, some modules are double sided or double banked, this used to only happen with every other power of two of increasing size to avoid using a whole 'nother address line for half the capacity of memory it could accomodate, so 1Mb 4mb 16Mb Simms were single bank and 2Mb 8Mb 32Mb SIMMs were double bank. Things advanced, motherboards got less picky about "half used" address lines, DRAM densities got to sizes where it was convenient to make a single bank in an "odd" power of two size, or for bigger sizes with smaller DRAMs 4 bank strategies were implemented on single modules. So to a motherboard a double banked SIMM or DIMM looks like two modules half the size. A quad banked module looks like 4 modules a quarter the size.

Now, that VIA apollo chipset wired up correctly, should see four banks of DIMMs however many sockets they are in, be it one, two or four. However, the motherboard manufacturers may have messed this up, allowing it to only see one or two banks in the DIMM socket. They may have split the banks evenly between DIMM and SIMM and not allow dynamic allocation of them according to which set of sockets needed them.

You, mentioned the 128Mb module having 8x "VT28SD16M8PC-7" now that reads as 16Mbit deep x 8bit wide, which means a 128Mbit DRAM, now the DRAM memory cell array is 128Mbit, but the chip makers can wire these up differently to give different depths and bit widths. A 128Mbit DRAM could be wired up inside the chip to be 4Mbitx32bit. or 8Mbitx16bit. 128Mbyte modules have been made up with many different sizes of DRAM in quite a few different formats. For instance with 64Mbit DRAMs, if the chips are 8Mbitx8bit, then to make a 64bit wide bank takes 8, however, this is only 64Mbyte, so therefore another bank of 8x 8Mbitx8bit is needed, resulting in a 2 bank 16 chip DIMM.

I am a little lost as to which particular DIMM you are reading as 4 banks, if it is the 256Mbyte DIMM with 16 DRAM devices on, then I believe that will mean there are 4 chips to a bank, meaning the chips are 16bits wide, and with each bank needing to be 64Mb to make up 256Mb total, then each chip will have to be 16Mbyte, which is 128Mbit, (whether it is 2 64Mbit arrays or not) so each bank is 8Mbit deep.  Now, if you use a utility that can tell how many banks the motherboard SEES, rather than one which reads the EEPROM, which is just saying what the module is, then you might find that although the chipset could read 4 banks if wired up correctly, that it is only seeing 2 in this case. In which case it is only able to address 4mbit deep into each DIMM also. It is not particularly unusual for a motherboard to only be able to see 2 banks on a DIMM, since only one or two chipsets handle 4 bank DIMMs and they were not so common as more conventional arrangements.

However, what this may now mean, since it would appear that if it is that 256Mb module is a 4 bank device and I beleive it's only seeing 2 banks, is that there is no arrangement of 128Mb DIMM that will work on this board :-(  restricted as you appear to be by a bank depth of 4Mbit and 2 banks, which is 64 Mbyte in 2 banks of 32Mbyte.

Hmmm one thought though, a bank or two may have become locked to the SIMM sockets due to previous use of SIMM memory in the board. Resetting the CMOS RAM may free this bank allocation to be used by the DIMM socket. Reset by jumper by the method recommended in  the manual. Do not tell me you have done it from inside BIOS setup, because it doesn't do the same thing.  If this is the case, the board may see two additional banks of the 256Mb DIMM (if that was the 4 banked one) and now count 128Mb at boot.

Well, if it does that, I wish I could tell you it is good news for getting a 128Mb DIMM working in there, but whether the board will refresh it correctly is entirely another matter, and although the BIOS routine can count it, it doesn't mean that it won't drop bits from inadequate refreshing while in use. :-(

regards,

Road Warrior
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Expert Comment

by:ComTech
ID: 6703852
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ID: 6975644
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Author Comment

by:detempel
ID: 6980225
I want to split the points as follows:
200 points to RoadWarrior
100 points to SysExpert

Please tell me how to split the points.

The original question hasn't been completely resolved but I have gathered a lot of information regarding the usage of memory on this old motherboard.

I might review this question when my brother asks me about putting in extra memory again ;-).
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by:Moondancer
ID: 6982194
Thank you, detempel, I have processed this point share for you.
Points for SysExpert -> http://www.experts-exchange.com/jsp/qShow.jsp?qid=20295631
Moondancer - EE Moderator
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Expert Comment

by:Bigfoot_Hunter
ID: 8788532
Delempel, you say you have got the manual for the motherboard. I have exactly the same motherboard, and am still looking for the manual. Do you have it in digital form?
I want to install a CPU with a multiplier of 3x, but I can't find the jumpers to set the multiplier. The print on the board states that I need jumpers BF0 and BF1 for that, but I can't find them... I was hoping that the manual would help here :-)
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Author Comment

by:detempel
ID: 8796171
Hi Bigfoot,

I had the manual in digital form but I'm afraid it is of to the bin because I recently 'lost' a partition with old stuff on it. The good news is I still have the manual in paper form.

BF0 en BF1 refers to the processor itself:

http://www.plasma-online.de/index.html?content=http%3A//www.plasma-online.de/english/upgrade/tweak/overclock/oc_locking.html

You are looking for jumper P1 which is located at the edge of the board between the AGP-socket and the processor.

JP1

1-2      3-4      Multiplier
OFF      OFF      1.5 and 3.5
ON      OFF      2
ON      ON      2.5
OFF      ON      3

Regards,
Gandalf.
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