Image Map Image Map
Results 1 to 7 of 7

Thread: Uprgade memory for 386SX

  1. #1

    Default Uprgade memory for 386SX

    Hi Guys!

    I'm going to upgrade memory for my 386SX and got several simple questions before I buy 30 pin SIMM on eBay.

    1) Current installed SIMMs has 9 chips, does it mean I have to buy SIMM which support parity?
    2) Current SIMMs are installed in pair, does it mean I have to do the same or I can put one SIMM only?
    3) What will happen if I put more than 16Mb? Will system still start with but can't see more then 16Mb?
    4) Do I need to check something else before buying SIMM I am not aware of? Like having the same specification with my current SIMMs or number of chips or amount of memory in one chip?

    Thanks!

  2. #2
    Join Date
    Aug 2006
    Location
    Chicagoland, Illinois, USA
    Posts
    5,471
    Blog Entries
    1

    Default

    You've answered most of your questions yourself You should buy what is already in there (parity), you will only see 16mb (386 can address 4gb but most 386sx systems were limited to 16mb for cost reasons). You might be able to get by with only one SIMM, but you should probably put in a pair. As for specs, make sure to buy the same speed or faster (ie. lower NS rating).
    Offering a bounty for:
    - The software "Overhead Express" (doesn't have to be original, can be a copy)
    - A working Sanyo MBC-775, Olivetti M24, or Logabax 1600
    - Documentation and original disks for: Panasonic Sr. Partner, Zenith Z-160 series
    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

  3. #3

    Default

    Quote Originally Posted by Trixter View Post
    You might be able to get by with only one SIMM, but you should probably put in a pair.
    I just don't see how you could get by with one 30 pin SIMM in a 386SX. 16 bits requires two 30 pin SIMMs.
    ☀☀☀ Visit Take Another Step for both computer and non-computer related discussions. ☀☀☀

    If you're looking for DS/DD or DS/HD 3" or 5" floppy disks, PM me. I've got some new, used, and factory over-labeled disks for sale.

    There is a crack in everything. That's how the light gets in. -- Leonard Cohen

  4. #4

    Default

    Thanks!

    Wanted to confirm if I put 16Mb in SIMMs so total will be 20Mb and system will still start but will show just 16Mb or even won't start?
    Also if I install SIMMs in pair do they have be exactly the same of just NS rating?

  5. #5
    Join Date
    May 2009
    Location
    Connecticut
    Posts
    3,949
    Blog Entries
    1

    Default

    Quote Originally Posted by djyuran View Post
    Thanks!

    Wanted to confirm if I put 16Mb in SIMMs so total will be 20Mb and system will still start but will show just 16Mb or even won't start?
    Also if I install SIMMs in pair do they have be exactly the same of just NS rating?
    Likely won't start with more than 16MB installed. I don't know all 386SX BIOSes so I can't be certain on this.

    Try to get two identical SIMMS if possible. Don't have to be the same NS; make sure the slower SIMM meets the requirements for the system.

  6. #6

    Default

    Quote Originally Posted by djyuran View Post
    1) Current installed SIMMs has 9 chips, does it mean I have to buy SIMM which support parity?
    Likely, but there may be some jumper or setup option to disable parity.
    Anyway, most of 30-pin SIMMs come with parity, so it doesn't make sense to try those without it.

    2) Current SIMMs are installed in pair, does it mean I have to do the same or I can put one SIMM only?
    You need a pair.

    3) What will happen if I put more than 16Mb? Will system still start with but can't see more then 16Mb?
    386SX can only directly address 16 MB.
    But there were some chipsets (eg. Suntac SuperSX) with EMS support, so it's possible you can use the extra RAM as EMS.

    4) Do I need to check something else before buying SIMM I am not aware of? Like having the same specification with my current SIMMs or number of chips or amount of memory in one chip?
    You want 4 MB SIMMs, right?
    Make sure your board supports them.
    While late 386SX boards (typicaly 33 or 40 MHz) do support them, the early ones may not.
    If you want some more help, then some info on your board is a must, probably a good photo.

  7. #7

    Default

    Quote Originally Posted by djyuran View Post
    Wanted to confirm if I put 16Mb in SIMMs so total will be 20Mb and system will still start but will show just 16Mb or even won't start?

    The address bus of a 386sx is only 24-bits wide, thus 2^24=16777216 bits (i.e.---16MB). You can put as much as you want in there, the CPU simply can't address more than 16MB. It's unlikely (but not impossible) that it would keep it from booting.

    REF: https://en.wikipedia.org/wiki/Intel_...0386SX_variant

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •