top view of Deico 486-DX VESA mainboard

Deico 486-DX VESA Local bus mainboard

Deico 486-DX VESA Local bus mainboard only supports 386DX, 486DLC, 486SX, 487SX and 486DX processors. The CPU is into one of three sockets and selectable by jumper JP27.

Deico 486-DX VESA mainboard has four memory connectors 2x 72 pin each.
Cache memory has two bankch, each selectable to 64 kB or 128 kB or 256 kB. Each cache memory bank contains four narrow DIL28 memory integrated circuits. Beside both cache memory banks, the mainboard has a TAG RAM of 16 kB.

The mainboard has 486DX ISA AMI BIOS with support of floppy discs, IDE hard disc, printer port, two serial ports, keyboard and mouse.
BIOS is stored in one EPROM 27C512. Here are images of this BIOS: (ZIP file contains EPROM images in HEX-Intel/Motorola/Tektronix and Binary formats) .

Expansion bus
The Deico 486-DX VESA mainboard has 16-bit expansion bus with six expansion-connectors and two shared VESA Local bus expansion-connectors

Producer:   Deico
Year:   1992
Origin:   Taiwan
Chips:   Symphony SL62C361 & SL62C362
RAM:   256 kB up to 4 MB, modules 2x 72 pins
Cache:   64 kB / 128 kB / 256 kB selectable by jumper
Support:   AMI BIOS 486DX 1992
Connectors:   1x parallel port, 2x serial, kbd & mouse, floppy disc, IDE hard disc
Interface:   6x ISA and 2x VESA shared
OS support:   MS WIN 3.1
Size:   219 x 330 mm


JP1 System 1-2   normal
2-3   reset CMOS
JP2 System 1-2   normal
2-3   emergency
JP3 Input/Output 1-2   enable
2-3   disable
JP4 LPT IRQ 1-2   LPT1 = IRQ7
2-3   LPT1 = IRQ5
3-4   no IRQ
JP5 COM1/3 IRQ 1-2   COM1/3 = IRQ4
2-3   COM1/3 = IRQ5
3-4   no IRQ
JP6 COM2/4 IRQ 1-2   COM2/4 = IRQ3
2-3   COM2/4 = IRQ9
3-4   no IRQ
JP8 Video 1-2   color
2-3   mono
JP9 Mouse 1-2   IRQ12
2-3   disable
JP11 VL-BUS wait states 1-2   0 wait state
2-3   1 wait state
JP12, JP13, JP14 CACHE Bank 2 selection 1-2   64 kB
2-3   128 kB
3-4   256 kB
JP16, JP17, JP18, JP19, JP20 CACHE Bank 2 selection 1-2   64 kB
2-3   128 kB
3-4   256 kB
JP21 CPU freq. 1-2   normal
2-3   not 50 MHz
JP22, JP23, JP30 CPU mfg. 1-2   other
2-3   Cyrix
JP27 CPU selection 1-2   486DX
3-4   487SX
5-6   486SX
7-8   386DX/486DLC
JP28, JP29 CACHE Bank 1 selection 1-2   486DX, 486SX or 386DX, 128KB
2-3   386DX, 64KB/128KB
JP31 CPU freq. 1-2   50 MHz
2-3   not 50 MHz
JP32 CPU freq. 1-2   not 50 MHz
2-3   50 MHz