View Full Version : 80286 Suntac Mainboard RAM Upgrade

January 18th, 2014, 12:22 PM
I got a Suntac 286 Mainboard, and i want to upgrade the System Memory i got several 41256 IC's.
But i need the DIP Switches Settings and i already maxed out all banks with 41256 IC's and played with DIP Switches.
Boots only with 1Mb and 512Kb Ram setting.
All other DIP Settings hang during memory count, only showing 64kb.

Here is a Picture of the Mainboard,


Thanks for Help :)

January 18th, 2014, 01:37 PM
Nice motherboard. Is that a Magitronic OEM? (Suntac is the chipset) What BIOS does it have?

Anyway 2 banks of 18 41256 chips are 1mb total. If that is similar to the one I have, the Suntac chipset supports using the memory as XMS or EMS (but not both).

What you want is memory "mode 2" A total of 18 DRAMs (41256-8 ) are inserted in to Bank 0, and a total of 18 DRAMS (41256-8 ) are inserted in to Bank 1. The DIP switches -6 -7 -8 are set to ON, OFF, and ON respectively. In Mode 2 the system memory size is 640k and XMS expansion memory size is 384k.

This is the mode you should use.

But this chipset also permits using using the 384k as EMS (with the suntac EMS driver installed) instead of XMS. If you want that then the switches -6 -7 -8 are ON OFF and OFF. Note that in this mode you can NOT use the extra memory as normal XMS and you will not be able to load DOS 5 or 6 in to XMS high memory.

If you were expecting more memory, you need 421000-8 DRAM chips for 2 MB (1 bank) or 4 MB (2 banks) of ram.

If you have a ISA memory card, the motherboard DIP switches should only be set to what is on the motherboard. The rest will be detected automatically, although any DIP switches on such a card would need to be correctly set up first.

January 19th, 2014, 01:24 AM
i have no ISA EMS Card :) i use currently the XMS Mode, here is a Full Picture, in Higher Resolution:

I don't know the Manufactor, and have no Manual at all, got it from a dutch man in the dosforum community.
it had a leaking Battery and a broken Keyboard Connector now its fixed and works again.

As you can see on the Picture it got 2 different Kinds of Memory on this Board, there is 1Mb already installed
4x 41256 and 4 of the bigger sized one's found on ISA Graphics Card. (It seems the Memory installed is 1024Kb + 256Kb.. with 1024Kb useable/detected)
i was thinking i can add 32 41256's to reach a total of 3Mbytes.
But it looks like the there is no way todo this, so i'm Stuck with 1Mb :)

Do you now where i can get the Suntac EMS Driver ?

421000 costs new around 2 Euro/Piece.. thats too expensive.