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EDO ram help 64mb recognized as 32mb

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pcm2a

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I bought a pair of IBM EDO laptop ram modules that are each labeled 64mb. I have two IBM laptops that I tried them in, a 560E and 380ED. Both of those laptops have one ram slot and in both the ram reads as 32 and not 64mb. I tried both modules in case one was bad.

In the below photo on the right is one of the 64mb modules that reads as 32mb. On the left is some unknown brand 64mb EDO ram (QC?). That ram module reads as 64mb in both laptops.

When I look up the chip model number on the QC ram it tells me it is 4x16. When I look at the sticker on the IBM it says 8x64. I have no idea the relation between those.

Does anyone have any ideas why the IBM ram would only read as 32? My only guess is the label is misleading and it is actually supposed to be 64mb when used as a pair.

20140707_171316.jpg
 
Well, the datasheet for the TC5165165AFT says that they're 4M x 16 bits each, or 8MB. You have 4 of them, so that's 32MB--unless the reverse side also has 4 chips, in which case it's 64MB as advertised. It's quite possible that neither of your laptops can handle 64MB in the single slot.

I have a similar issue with a 512MB PC133 SIMM--it's not recognized as such in a lot of older gear and reverts to 256MB. Not a lot I can do about it.
 
I was worried that my original post wasn't 100% clear after I submitted it. The QC module (pictured on the left), does have 4 chips on the back, and in both laptops it reads 64mb. It is a 64mb module that works perfectly in both laptops. Both laptops can handle a 64mb module, at least this module.

The problem is why doesn't the IBM ram (pictured on the right) also read 64mb? Hopefully figuring out why the IBM modules read wrong will tell me what type of ram to target.

The breakdown of the IBM ram chip model says:
016 = 64 Megabit chip
80 = 2Meg x 8
P = 3,3 volt low power

Here is some details on the ram slot on the 380ED:
Processor Type Pentium MMX 166/66 MHz / 64 bit transfer to L2 cache / 64 bit transfer to memory
Memory - std / max 16 MB / 80 MB / non-parity / 3.3 volt / EDO
Memory - features 1 socket for one JEDEC 144 pin EDO SO DIMM of 8, 16, 32, or 64 MB / socket accessed from bottom via screw
 
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I think the label is incorrect, or you have a bad chip.
 
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There are two of them, so that means both chips have gone bad to the point that they are both 32mb or both are mislabeled. They seem to both work fine in win98, but I didn't try any kind of memory stress program to see if it would cause them to fail. Maybe I should try that tomorrow.
 
So who can break down these two things.

On the sticker it says 8x64. Does that imply 32mb?

Looking at the chip I get 2x8. Does that mean 4mb per chip?
 
It's unlikely it's a bad chip. Only one RAS or die in a multi-die configuration would have to be bad for 4M to work but not 8M. The four chips are paralleled supporting two CAS each.

The only link I can find is this test report which also had problems with a similar module: http://beta1.ipc2u.by/files/add/doc/133961/RAMTABELLE2.pdf

I can't find any more specifics on the IBM part numbers. I'm curious what is in the EPROM. I think you got a mislabeled part.
 
There aren't enough PINS on the chips on that IBM for it to be more than a 32M stick.
 
Wow, I didn't look at the pins on the chips. Great catch.
 
If it's double sided and each chip is 8 bits wide (x8 total chips = 64 bits), there are plenty. 32 pins - 12 address (16 M), 8 data, 1x CAS, 1x RAS, WE, CE, CLK, CKE, VCC, GND = 4 pins left over.

And where are you getting 'EDO'? These look like SO-DIMM 144s. That's synchronous RAM. (SDR SDRAM).

It could be these DIMM have only 1 RAS and 12 address lines (2^(12*2)) and your old DIMMs judging by the pin count may have 2 RAS lines and 11 address bits. If the laptop only supports reaching 8M addresses through 2 RAS lines (2^((11*2)+1)) then that could explain why these are only showing up as 32 MByte.
 
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We know they are EDO for a few reasons, for one they work in 3 laptops that only take EDO ram. Another, if you look up the model number you will find them listed all over the "net" as EDO 64mb sticks. Third if you break down the model number on the chip, I used this site http://www.chipmunk.nl/DRAM/IBM.htm, it also says it is EDO.

So if I wanted to pick up a 64mb stick of EDO ram that has the best chance of working I should look for sticks with twice as many pins, with the assumption that it will have two RAS lines? For example, I just went to ebay and looked up "64mb EDO 144" and the top few choices all have double the pins compared to my IBM stick.

Update: I looked at all of the 64mb sticks up on ebay and I only see one other one, toshiba, that has pins like the IBM. All the rest have double the pins.
 
I see now. I had no idea async RAM came in 144 SO-DIMMs complete with EEPROMs. I learned something today, thanks!

According to the IBM part number break-down, those are 64Mbit chips. As long as there are 4 of them on both sides, that's 64 Mbyte. That IBM site did not break down the geometry, but if it's similar to the 16Mbit IBM parts, they are likely 8 bits wide with 12+11 bit row/column width and a single RAS. There are also plenty of pins for that configuration on the IC.

So if they are indeed 8 RAM chips per DIMM, my guess is still the same as my previous post. The laptop supports 2 RAS lines with either a 11+11, 10+12, or 12+10 row/column widths only and these DIMMs are 11+12 or 12+11 width with a single RAS.

If you have a Bus Pirate or similar device you could fly wire to the EEPROM and dump the configuration to know for sure (or XRay the PCB and trace it out by hand!)
 
What are the thoughts on using this bizarro ram as the 32mb that it is recognized at? I have an IBM 760ED that has two ram slots, the maximum in each is 32mb. When I put one of the sticks in everything seems great, it is recognized as 32mb. When I put both sticks in they are recognized together as 64mb total, but it is a crap shoot whether I even get booted into win95. If I do make it into win95 it is only a matter of time before everything locks up.

So my concern is, if I only use one stick could there be some memory side effects that I haven't encountered yet?

What is a good memory testing application that will run in win9x that doesn't require booting from a cd?
 
Does that kernel switch between reboots or between full reinstalls? Meaning if I boot up with 16mb then reboot with 48.
 
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