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Thread: Uprgade memory for 386SX

  1. #11

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    Quote Originally Posted by Stone View Post
    Why didn't you try 4 MB in slots 1, 2, 3 and 4? IOW, fill Banks 0 and 1 with 4MB SIMMS.

    See if that doesn't work.
    I don't have four 4Mb SIMMs but since #1 and #4 observations I'm skeptical if it can work unless someone can provide me with logical explanation

  2. #12
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    What motherboard are you using and is the 386sx a soldered on part or the removable type with pins? Intel did make 386sx PGA chips (not very common) and motherboards meant for a full 386 chip need RAM installed in groups of 4 identical SIMMs or you get memory errors (they are meant for 32 bit RAM). The soldered on 386sx boards have a 16 bit memory bus so you can use 2 SIMM at a time like a 286.

    There are also boards like the Chaintec 325SCD where the 8 SIMM slots are laid out in BANK 0 then Bank 1 then Bank 0 then Bank 1 so you need to skip a slot when installing RAM (unlike most motherboards where you put all 4 in a row for each bank).
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  3. #13

  4. #14

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    Quote Originally Posted by djyuran View Post
    Why is it so weird? How can I get full 16Mb then?
    That solution was already suggested.

    Quote Originally Posted by Stone View Post
    Why didn't you try 4 MB in slots 1, 2, 3 and 4? IOW, fill Banks 0 and 1 with 4MB SIMMS.
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

  5. #15

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    Quote Originally Posted by Unknown_K View Post
    What motherboard are you using and is the 386sx a soldered on part or the removable type with pins?
    It's soldered but I am sure how to say what motherboard I have. I put schema from data sheet - https://ibb.co/DfZD1VW, is it enough or I need to look for something else?
    Anyway configuration 1 + 1 + 4 + 4 in Banks 1-4 works so looks like SIMMs don't have to be identical

    There are also boards like the Chaintec 325SCD where the 8 SIMM slots are laid out in BANK 0 then Bank 1 then Bnk 0 then Bank 1 so you need to skip a slot when installing RAM (unlike most motherboards where you put all 4 in a row for each bank).
    I can try that

  6. #16

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    Quote Originally Posted by Xacalite View Post
    Thanks! It explains everything! I couldn't think if motherboard supports just predetermined configuration of SIMMs dispositions.

  7. #17
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    Just a side note on parity SIMMs. Back in the day, DRAM was pretty expensive, so some enterprising manufacturers put 8 DRAMs on the SIMM PCB and then "faked" the ninth bit with a parity generator chip. So you have 9 chips, but only 8 of them are RAM.

  8. #18

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    Finally I got 2 more 4mb SIMMs and got 16Mb in 4mb-4mb-4mb-4mb configuration.
    Thanks!

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