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Mixing different size of 72-pin EDO SO-DIMM ( Laptop memory RAM ) ?

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123434
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Mixing different size of 72-pin EDO SO-DIMM ( Laptop memory RAM ) ?

#1 Post by 123434 » Fri Jan 05, 2018 12:38 am

Hello ( 1998 Pentium 1 laptop )
Mixing different sizes of 72-pin EDO SO-DIMM ( Laptop memory RAM ) ?
  • 4 MB
  • 8 MB
  • 16 MB
  • 32 MB
  • (64 MB) Don't know if 64 MB exists ?
- So I have 2 slots is it possible to mix these different MBs and will the laptop recognize all mixes ?
Like:
Slot0= 32MB, Slot1= 8 MB => 40 MB ( Total ) ?
Slot0= 32MB, Slot1= 4 MB => 36 MB ( Total ) ?
Slot0= 32MB, Slot1= 16 MB => 48 MB ( Total ) ?
and such...
Or do I need same size ones ?
8 and 8 => 16 MB
16 and 16 => 32 MB
32 and 32 => 64 MB

Also are all 72-pin EDO SO-DIMMs the same ?

if made in USA ?
if made in Europe ?
if made in Asia ?
Or are all compatible with each other ? ( Examples below )
- Siemens GERMANY 6ES7478-1AP00, HYM324025GD-60
- Smart USA SM5CSC8M32003
- GLOBAL MEMORY GMEFPM646044SK

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Re: Mixing different size of 72-pin EDO SO-DIMM ( Laptop memory RAM ) ?

#2 Post by rkawakami » Fri Jan 05, 2018 4:51 pm

Mixing memory sizes?
You should be able to freely mix-and-match memory module capacity, up to any system/firmware maximum size limitation. I do not recall there being any requirement for "matched sets" in those days. In some cases you may need to use one socket before the other, or in other cases, put the larger module of the two in a certain socket. I'm assuming that you have already tired to consult the manual for the system, if you have it. That would be your best guidance but note that with improvement in memory manufacturing occurring at that time (late 1980's), module sizes that did not exist at the time of the system's release may also work later on. This was the case many times when IBM stated a certain maximum memory size for a system, but neglected to formally update that information when larger modules were introduced.

Are all 72-pin EDO SODIMMs the same?
There can be some things that affect compatibility, but as long as they are functionally the same then you should be okay. As long as they were spec'ed to one of the industry-standard access time values, in other words. Modules usually have a nanosecond (nS) speed grade printed on the label (i.e. -60 or -70 for 60nS or 70nS access time). You probably will not find anything lower than 60nS for EDO memory.

Another thing to consider is that there could be some 3.3V modules (vs. 5V, which was the norm). Physically, the 3.3V modules should not be able to be plugged into a 5V slot (and vice versa) due to keying along the edge of the module. However, if you buy a module sight unseen that is supposed to be for a 5V system and it's actually a 3.3V, then you'll find out about it when you are attempting to plug it in. By that time you may not be able to return it.

Now there can be other major show-stoppers if you think that all 72-pin modules are the same. There were options for error correction (ECC) which more than likely will not work in your computer. You can usually identify those modules by them having 9 individual 'chips' on the board (instead of 8). There were also earlier-technology memory that was called Fast Page Mode (FPM) that were functionally almost the same as EDO (Extended Data Out). In some cases those FPM modules could be used in the same system that also allowed for EDO, but I don't believe that you could mix them.

As far as there being differences between countries of origin, that shouldn't be too much of a problem. When EDO was new, most everyone in the DRAM industry was making them (US, Germany, Taiwan, Japan). What you generally have to watch out for are modules being offered by small companies who were "cutting corners" by using a less-than-optimal printed circuit board design for the module or not completely testing the module after it was assembled. If you stick with the major manufacturers of that time (Micron, Siemens, Toshiba, Mitsubushi, Vitelic [was employed there for some time], Hyundai [now Hynix], Nanya; not a complete list), then you'll have a better chance of getting something that's reliable (after all this time).

I would strongly recommend that whatever memory you install in the system be fully tested before you commit to using it. You can download a memory diagnostic which will perform a fairly exhaustive test for here: http://memtest.org/#downiso
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123434
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Re: Mixing different size of 72-pin EDO SO-DIMM ( Laptop memory RAM ) ?

#3 Post by 123434 » Mon Jan 08, 2018 12:23 am

Ok. I bought earlier ebay's 10$ Smart "Cisco" 32MB EDO 72-pin that turned out to be 3.3V. Somebody said they are from network devices and not a regular laptop memory.

My laptop started to windows with irregular *beep beep beep*-sound and it did not recognize the memory. I Found out later that it needs 5V memory.
-> So how to know if the 3.3V memory comb is now broken ? I have a multimeter is it any good tester ?
-> In my newer 2011 HP DV7 AMD A6-3410 Laptop I can use both DDR3L(low voltage 1.35 V) and regular DDR3(1.50 V) is it the same ?

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Re: Mixing different size of 72-pin EDO SO-DIMM ( Laptop memory RAM ) ?

#4 Post by thinkpadcollection » Mon Jan 08, 2018 4:09 pm

Pentium ( Not Pentium 1) computers typically use EDO unbuffered non-ECC does your module say ECC on it or chip count is odd like 9 or 18 chips, then this is ECC and not compatible. (has to be 8 or 16 chips per module which is non-ECC which is only way to work, also 3.3V for this pentium notebook). Since this pentium notebook is 64bit wide, you can run mixed especially using 144pin SO-DIMM EDO, if notebook uses SO-DIMM 72pin, you have no choice but run matched pairs to get 64bit datapath per bank. Desktop Pentium (old ones, like Pentium 100, 133, 200, or Pentium MMX with 72 pin simms requires two matched pairs per bank because 72pin simm memory are 32 bits wide each. For desktop pentium that uses SDRAM 168 pins simms which is 64bits wide each, that's 1 module per bank.

Your HP notebook with AMD A6-3410 can have EITHER: 1.5V or 1.35V not mixed. Get matched pair of 1.35V (DDR3L or PC3L) to get best battery runtime and cooler, also best performance especially video performance in dual channel mode using matched memory sticks, either 2x 4GB or 2x 8GB. Guaranteed to work first try, please get a matched pair from ebay with OEM logos like Elpida, Hynix, Samsung, Micron or Crucial, for third party memory that is KNOWN to work right out of box are Kingston or Mushkin.

In ebay search box: "DDR3L-1600 2x4GB Micron" because AMD A6-3410 requires DDR3L-1600 or PC3L-12800 (both are same speed) or change search string for 16GB total: DDR3L-1600 2x8GB Samsung. Change the OEM name to find them and pick one with best price and if you prefer pick one that is from USA.

DIMM is desktop and longer module. SO-DIMM is shorter and is intended for notebooks.

Note: Do not get confused with later computers that use newer Pentium M or Pentium (always with model type of processor).

Cheers, thinkpadcollection

123434
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Re: Mixing different size of 72-pin EDO SO-DIMM ( Laptop memory RAM ) ?

#5 Post by 123434 » Tue Jan 09, 2018 12:23 am

Hello I bought earlier a RAM comb from Ebay: "Smart Cisco 32MB EDO 72-pin SO-DIMM"
SM5CSC8M32003 / SM32L4E88-60-SP9D ( USA year 1999 )
for the all-in-one/laptop PC Siemens Nixdorf PG720PI 1998:
  • AMD K6 233 Mhz little foot. Socket 7 mainboard.
I asked about it in this forum:
http://www.vogons.org/viewtopic.php?f=4 ... 84#p639484
Turned out it is 3.3V Network device-memory and not PC memory...?
What can I do with it and how to know if it is broken ? Is it really only for routers/switches ?

- Can someone confirm that I need 5V EDO 72-PIN SO-DIMM for socket 7 mainboard and that is the working memory for that PC ?
-> Original memory is 16MB= HYM324025GD-60 and there are 4-slots.
http://i162.photobucket.com/albums/t278 ... 3onmbs.jpg

The ebay.com seller knew nothing about the SMART CISCO-combs he "just sells them" :mrgreen:

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Re: Mixing different size of 72-pin EDO SO-DIMM ( Laptop memory RAM ) ?

#6 Post by thinkpadcollection » Tue Jan 09, 2018 2:53 am

I understood you have 2x 16MB and one 32MB in the computer? (I did find you on other forum VOGONS). I happen to know ancient stuff as I worked with countless socket 5 or 7 machines for long time back then.
This CPU K6 233 IS socket 7 which Pentium 233MMX (much faster FPU) can fit as well. K6, K6-2 and any Intel Pentium processors means you DO need to install memory in pairs in bank 0 and 1 this is reason why this failed to start because bank 1 is missing one of two pair of memory modules. Especially any 72pin DIMMs or 72pin SO-DIMMs, Since 72pin modules are 32 bit each and socket 5 and 7 processors communicates in 64 bit data path even processor is 32bit but this is done for performance reasons for pentium originally designed by Intel. EDO 144pin and SDRAM DIMMs is 64bits wide and not compatible with yours anyway.

Order pair of 16MB EDO SODIMMs 72 pin 5V from ebay. Note the height of the SO-DIMMs vs your for cisco this is the reason not to buy like this if it says for odd machines that is for networking, do not buy.

https://www.ebay.ca/itm/32MB-2x16MB-72p ... SwcLxYEAp8

Memory banks I know is anachronism term for anyone who is not familiar with this, it dates back to when bank switching is common due to large number of 1 bit wide chips in rows in groups at a time for certain number of bits that processors is designed with and memory was not that large back then as well. To produce sufficient memory capacity for example 16 bit processors and needs 512KB using 64KB x 1bit chips means 4 banks of sixteen chips each. Some of them actually had early ECC means either 1 or 2, even 3 more chip for every 8 chips.

An early IBM PC with 64K motherboard to reach 640K needed nine banks of 9 chips each using 64MB x 1bit because processor was 8088 is 8 bit plus 1 extra for parity. Very late 8088 clone boards actually used eight 1MB x 1bit (most clones back then did not use parity either) still seen as 640K.

Imagine all you do need to make 1MB for 286 machine is pair of 256K x 16bits chips which is adds up to 1MB.

Cheers, Thinkpadcollection

123434
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Re: Mixing different size of 72-pin EDO SO-DIMM ( Laptop memory RAM ) ?

#7 Post by 123434 » Wed Jan 10, 2018 5:25 am

Yes. I have 2x16MB(Pair) Korean made Hyundai-chip memory in the computer very similar if not same as in ebay.com link:
https://www.ebay.ca/itm/32MB-2x16MB-72p ... SwcLxYEAp8

I know now to:
1.) Check the height of the memory comb so it fits the 4-slot holder.
2.) Voltage 5V EDO SO-DIMM 72-pin.
3.) Order 2pcs pair of them. (Otherwise computer seems to *beep,beep,beep* at start-up.)
SLOT0, SLOT1,
SLOT2, SLOT3
  • So...I can have 2(pair) from one manufacturer and 2(pair) from other manufacturer ?
    Or do I need all from the same manufacturer like all 4 pcs from Hyundai ?

Socket 7 also seems very universal and expandable= AMD K6-III(3) 450 MHz is probably the best processor for it.

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Re: Mixing different size of 72-pin EDO SO-DIMM ( Laptop memory RAM ) ?

#8 Post by thinkpadcollection » Wed Jan 17, 2018 7:48 pm

Hey, yes different makes in matched pairs means two sets of different ones are correct, you heard that right.

Any luck yet?

Cheers, thinkpadcollection

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Re: Mixing different size of 72-pin EDO SO-DIMM ( Laptop memory RAM ) ?

#9 Post by Cooler22 » Sun Feb 11, 2018 1:14 am

AFAIK on the 701c it can only accept FPM memory, one of the highly sought after 64MB Samsung FPM SODIMM only works on it unless the chipset is upgraded from an Opti MVA to an MVB revision. I have yet to confirm the rumor but in your case it's likely that EDO RAM will most likely combine at 64MB's if your chipset can support it, in which likely will.

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