View Full Version : Need documentation on Cumulus "Newmark 386 SX" AT-SX ISA add-in board

January 21st, 2017, 09:29 AM
I got one of these from another forum member, obviously a "stump the chump" challenge...

Cumulus "Newmark 386 SX" AT-SX mainboard P/N 820261
4 30 pin SIMM sockets
387SX-16 surface mount
387SX socket
WDC 37C65CJM - floppy controller
TI TL16C452FN - Dual UART (up to 256Kb!) with Parallel Port And Without FIFO 68-PLCC

VIA FlexSet AT/PC - available at Datasheet Archive
VIA SL9030 Integrated Peripheral Controller, 24 bit address.
VIA SL9011 System Controller 286, 386 SX and DX up to 25MHz
VIA SL9250 (SL9251) 386SX Page Interleave Memory Controller
VIA SL9020 Data Controller
VIA SL9025 Address Controller, 256Kb, 1Mb, 4Mb chips

Some sort of a encapsulated RTC, akin to a Dallas
5 osc
9.6000MHz - 300kb/s used by AT floppies
16.0000MHz - 500, 250, 125 KB/s floppy data rate

Bypass Board PN 8020266 looks to be a "bridge", a header on the top side, one on the bottom, may be to overcome PCB limitations? I see no components on it.

AT-SX VGA Board PN 8020XXX
Tseng ET4000AX
2x AAA1M304P-08 Dynamic RAM, Fast Page, 256K x 4, 20 Pin NMB Technologies
3 osc, 25.1750MHz
20 pin header