Yes it is possible, but not straightforward. They're all Async DRAM modules but it will take some focus to both adapt the physical difference and match the addressing bits. The ICs cannot just be swapped out in most cases. 30-pin SIMMs are 8-bit wide memory and 72-pin SIMMs are 32-bit. The IC's on the modules will need to add up to the appropriate value. Personally I have recently looked into doing a project like this. I can't find 30-pin SIMMs/SIPPs either so I think it would be easier to design and build my own PCBs around ICs off of 72-pin SIMMs. An easier swap is actually SIPPs and 30-pin SIMMs since they're the same thing just with difference physical connectors.

Can you get 30 pin modules shipped out of country?

One thing is 95 on a 386 will be very painfully slow.

If you are running programs that need more than 2 MB of RAM, you are using the wrong machine 😀

Get a 486 or Pentium.

Yes indeed, for running win95 you need at last a faster 486 system or a pentium one.. You can always try on ebay for 30 pin simm, but running w95 and doom on a 386 is just a no go.

Doom and 95 pretty much need a 486 at the least to run ok.
386s are almost half the speed as a 486 clock for clock in some applications

It's a good idea to do a custom PCB and attach the IC's, maybe i'll do it..
I can get 30pin simms shipped from out of my country but I was thinking of converting because I have like 30 of 72pin simms
Didnt' know that the 386 was soooo slow, hmm, but anyways, I want to try win95! just for fun 😜, I've already got a 486 and a Pentium!

What speed is your SX? If it's 16 or 25 then even Windows 3.1 runs slow. Overall system has to be good. A few month ago I run Win95 on 386DX-40, 32MB ram, ISA VGA (Windows accelerator) on CF card and it run quite nicely.

Ebay is your friend for buying old stuff. You should get two 4MB simms to run win95 (slowly).

The whole purpose of a SIMMverter was so you could recycle the RAM from your older motherboard until you could buy new RAM. There was no reason to make an adapter that went the other way. You have to consider that the memory controller on the older motherboard is made to work with 30 pin modules. It may not know what to do with 72 pin memory. You can't just connect up 30 pins and leave the other 42 not connected to anything. If it is possible, it will require a lot more work (and probably some custom IC's) than it's worth. Also, the 386SX has a crippled memory bus to make the motherboards cheaper to manufacture. You're not going to be able to install massive amounts of RAM on them in the first place.

Coincidentally this whole project is what I've been studying in my spare time this month. I got a laptop in March which uses a 386SX and SIPPs, so my curiousity has been if I can take any SIMM, find datasheets on its asynchronous DRAM ICs, and then design a PCB to use those harvested ICs. I want a pair of 8MB modules and it's fun learning about these things. Personally, I've found it a better use of my time to study how memory works than to look for them and discover the only option is paying a neckbeard on ebay $80 for ancient untested sticks of ram. What I haven't gone far into yet is ordering new ICs from a distributor since they'd have datasheets available. The parts will wait until I understand it more. Though I did manage to get a 386 combo system with 30-pin SIMMs for $1 at the fleamarket a few weeks ago. I've found datasheets for its ICs and that's helped me even more.

The extra pins on the 72-pin SIMMs actually can be ignored. It's the memory controller's job is to abstract whatever configuration of ICs are present into the scheme the CPU wants for accessing memory. Memory controllers are usually paired to a particular CPU architecture for this. The 386SX's memory controller is a simpleton and would be fine not having presence detect, CAS1-3, RAS1-3, DATA16-31, and Parity1-3 connected. The problem is that a lot of memory access is lost. Depending on the module configuration, a 64MB could turn into 8MB or something (which for a 386SX I guess that's not really too bad either). But on the otherhand, an 8MB could turn into a 512kB, making it nearly useless.
A 4MB memory module is logically 11 address pins, using all 11 columns and 11 rows. It gets to that depending on how the ICs are connected to the slot and onto the memory controller.
For instance to get a 4MB 30-pin SIMM module, the ICs could be:
8x 4Mbit x 1-bit
8x 2Mbit x 4-bit
8x 512kbit x 8-bit
4x 2Mbit x 4-bit
4x 1Mbit x 8-bit
2x 4Mbit x 4-bit
2x 2Mbit x 8-bit
1x 4Mbit x 8-bit (one IC is the module itself)
I forgot to mention pin packages as well.

Thanks Auzner for that great information! I understand it completely, and part of it is what I thought too!, if I have time this weekend I'll try to solder wires scrapped from an IDE cable in the solder points from the back of the 386 motherboard of two simm slots, and i'll solder the cables to the 72pin simms... I think I've got 32mb simms...
Kixs, the SX is 40mhz 😁

santysos wrote:

Thanks Auzner for that great information! I understand it completely, and part of it is what I thought too!, if I have time this weekend I'll try to solder wires scrapped from an IDE cable in the solder points from the back of the 386 motherboard of two simm slots, and i'll solder the cables to the 72pin simms... I think I've got 32mb simms...
Kixs, the SX is 40mhz 😁

Please don't waste those precious 32 MB modules!!!

What are the part numbers for the ICs? I've found some more info, lecture 3 in particular: http://www.ece.umd.edu/class/enee759h.S2003/ It would be great if there were video lectures of these slides.

A 386SX is limited to 16mb of memory, which is easily achievable with 4mb 30-pin SIMMS which are still available. Any project to put 72-pin SIMMS to work on a 386SX motherboard is a waste of time.

http://www.ebay.com/itm/16MB-4-x-4MB-30-pin-P … =item20db4b7d0f

Here you go. For $18 you can max out any 386SX motherboard with 4 RAM slots. You can't use more than 16mb of memory with a 386SX because the address lines needed to use more memory don't exist on either the chip or the motherboard.

Auzner wrote:

An easier swap is actually SIPPs and 30-pin SIMMs since they're the same thing just with difference physical connectors.

And good luck finding SIPPS with capacities higher than 256k. The reason why people solder legs onto 30-pin SIMMS for use in boards with SIPP sockets is BECAUSE they can't find high density modules that are affordable. 256k SIPPS are easy to find and cheap. Higher densities than that don't come up for sale often and command high prices when they do.

I have more reasons than I have shared for the way I am approaching this. I appreciate the link, I'm probably going to also buy a set if I don't see any more at the next fleamarket. The OP doesn't have any of these options and has to hack it. I am already aware of the exact reasons for the memory limitations and the traits of each module. santysos has already followed up that they will solder and find out the results. I'm glad that I've been able to help somebody with a similar project so far. My end goal isn't to game on this very particular system nor follow the cookie cutter 486 + 3DFX + SB build. The entire essence of this forum is old worthless techno-junk, are we really going to argue the sub categories of which junk is not as junky?

cookie cutter 486 + 3DFX + SB build

486 with 3dfx is a painful setup, it's all about giving you reason to think you can play something and not letting you enjoy it afterwards. It's like saying "Do you want a cookie?" while not having any cookie in the first place.

The entire essence of this forum is old worthless techno-junk, are we really going to argue the sub categories of which junk is not as junky?

One part of me is offended and wants to cry out "What did you call worthless junk?" and the other is giggling "That's what we do all the time"

Auzner, of what SIMM do you want the ICs p/n?
Thanks for the link and the info sliderider!, but i'm in Uruguay and getting things from other countries it's a bit hard, also with the shipping the cost would be like $35 for me..

I've checked my SIMM-box 😜, and I found that i've got lots of EDO SIMMS that don't know exactly why but don't work with my 486 so I can't use them in the 386 I suppose, in the other side i've got lots of 4mb FPM 72pin SIMMS that I don't want to use because they're too small, two 8mb, and two 16mb, so i'm going to use the two 16mb ones (that would give me 8mb of RAM, because the 386 will see them as if they were 4mb each).

I'll solder wires from a floppy cable in the solder "points" from the back of the motherboard, and it's a bit cheesy but, first i'll try, for not ruining the simms soldering them, peeling the tip of each wire and passing them thru the little holes in each pin of the SIMM http://upload.wikimedia.org/wikipedia/commons … dules_sm_hy.jpg (I tryed doing that, measured with a tester if it was making contact, and it was doing 😜), anyways, if that doesn't work, i'll solder everything.

Stay tuned 😜

I'm looking for datasheets of any IC for async dram of 'high density.' I want to become more familiar with the packages like SOJ they use, and determine if there is a common convention for pinouts. Sometimes I am lucky and things on ebay result in entire module datasheets: http://www.datasheetarchive.com/dl/Scans-065/ … 2IH00164255.pdf

If you are still interested, check this Re: Thinking of doing the 16mb GuS ram mod
I've mentioned a PCB adapter we've designed in Russia. It was originally made for GUS 16mb upgrade, but I guess that it could be used on some 386 rigs as well.

Hi guys, I have processed a lot of data to generate out my database of vintage SIMM and SIPP DRAM chips and modules:

http://martenelectric.cz/simm-sipp-ram-chip-database.html

This should be handy for those brewing at home 😀