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GeneralRe: I was so angry last week... Pin
Cp-Coder20-Oct-21 6:20
Cp-Coder20-Oct-21 6:20 
Generala question about laptop RAM type Pin
Southmountain19-Oct-21 8:28
Southmountain19-Oct-21 8:28 
GeneralRe: a question about laptop RAM type Pin
RickZeeland19-Oct-21 8:43
mveRickZeeland19-Oct-21 8:43 
GeneralRe: a question about laptop RAM type Pin
Southmountain19-Oct-21 8:56
Southmountain19-Oct-21 8:56 
GeneralRe: a question about laptop RAM type Pin
RickZeeland19-Oct-21 9:07
mveRickZeeland19-Oct-21 9:07 
GeneralRe: a question about laptop RAM type Pin
Daniel Pfeffer19-Oct-21 9:04
professionalDaniel Pfeffer19-Oct-21 9:04 
GeneralRe: a question about laptop RAM type Pin
Southmountain19-Oct-21 9:17
Southmountain19-Oct-21 9:17 
GeneralRe: a question about laptop RAM type Pin
ElectronProgrammer20-Oct-21 9:49
ElectronProgrammer20-Oct-21 9:49 
Daniel Pfeffer wrote:
They are not compatible with each other!


Actually they are electrically and protocol compatible but are not physically compatible because SO-DIMMs (laptop memory) are smaller than DIMM (desktop memory). If you search, there are pass-through adapters to connect SO-DIMMs to DIMM slots (but not the other way around since DIMMs would never fit inside a laptop).

The difference in pins is due to DIMMs having many "NC" ("Not connected") and reserved pins. Maybe for planned features that were never implemented (maybe more address pins for bigger memories but was scraped because they would be too expensive and no one would buy them?).

Daniel Pfeffer wrote:
If you have a two-slot model, you should buy the same type of memory (manufacturer, size) for the second slot that is present in the first slot of your laptop


Even though just adding a second SO-DIMM module with the same characteristics from the same manufacturer usually works (I have done this successfully), the recommendation is to buy a pair of SO-DIMMs and replace all memory.

Because slight differences in timings in modules produced at different times can lead to read/write errors which can translate into slow memory (due to retries or memory page faults) or worse, random reboots of the computer (which also happened to me before because I didn't follow the recommendation).

Memory sold in pairs (or in fours) is tested together and has a manufacturer warranty that they read/write exactly at the same time within the specifications.

For all interested:

* SRAM, DRAM, SIMM, DIMM, RIMM, etc define RAM architecture
* EDO (DRAM), SDR(SIMM, DIMM), DDRx (SIMM, DIMM), etc define the communication protocol and electrical connections which is also dependent on architecture
* SO(SIMM, DIMM), etc define the packaging

@Southmountain, as others said, you should check your laptop manufacturer for compatible memory and preferably buy memory that is on their compatibility list for assured stability. If you want something that is not on their list try to match the timings with something that is on their list. Example: you want memory with timings 7-7-7-21 but the fastest memory on the compatibility list is 8-8-8-24 then you should not buy that one and go for one that is 8-8-8-24 or slower. If you buy just one module to add to an existing one, put your system with both modules through a stress test to make sure that, if it fails, it will likely fail during the test (and not during some important work) and early enough for you to return it. Otherwise, because memories are so fast, errors may occur without you even being aware of until it fails catastrophically (laptop random reboot or programs crashing).
GeneralRe: a question about laptop RAM type Pin
Southmountain23-Oct-21 16:29
Southmountain23-Oct-21 16:29 
GeneralRe: a question about laptop RAM type Pin
David O'Neil19-Oct-21 15:45
professionalDavid O'Neil19-Oct-21 15:45 
GeneralRe: a question about laptop RAM type Pin
Southmountain20-Oct-21 5:48
Southmountain20-Oct-21 5:48 
GeneralRe: a question about laptop RAM type Pin
charlieg19-Oct-21 15:49
charlieg19-Oct-21 15:49 
GeneralRe: a question about laptop RAM type Pin
Southmountain19-Oct-21 16:42
Southmountain19-Oct-21 16:42 
GeneralRe: a question about laptop RAM type Pin
milo-xml20-Oct-21 1:28
professionalmilo-xml20-Oct-21 1:28 
GeneralRe: a question about laptop RAM type Pin
GuyThiebaut19-Oct-21 22:29
professionalGuyThiebaut19-Oct-21 22:29 
GeneralRe: a question about laptop RAM type Pin
Richard MacCutchan19-Oct-21 22:35
mveRichard MacCutchan19-Oct-21 22:35 
GeneralRe: a question about laptop RAM type Pin
Southmountain20-Oct-21 5:46
Southmountain20-Oct-21 5:46 
GeneralRe: a question about laptop RAM type Pin
CodeZombie6220-Oct-21 2:44
CodeZombie6220-Oct-21 2:44 
GeneralRe: a question about laptop RAM type Pin
Dan Neely20-Oct-21 2:48
Dan Neely20-Oct-21 2:48 
GeneralRe: a question about laptop RAM type Pin
Southmountain20-Oct-21 5:46
Southmountain20-Oct-21 5:46 
GeneralI have been going round and round in circles all afternoon... Pin
OriginalGriff19-Oct-21 5:25
mveOriginalGriff19-Oct-21 5:25 
GeneralRe: I have been going round and round in circles all afternoon... Pin
kmoorevs19-Oct-21 7:20
kmoorevs19-Oct-21 7:20 
GeneralRe: I have been going round and round in circles all afternoon... Pin
stoneyowl219-Oct-21 7:20
stoneyowl219-Oct-21 7:20 
GeneralRe: I have been going round and round in circles all afternoon... Pin
yacCarsten19-Oct-21 11:48
yacCarsten19-Oct-21 11:48 
GeneralRe: I have been going round and round in circles all afternoon... Pin
Richard Andrew x6419-Oct-21 7:31
professionalRichard Andrew x6419-Oct-21 7:31 

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