MICRONICS MOTHERBOARD

80486SX-25 (Baby size 09-00145-xx)

This document is for the baby-sized (13.3" x 8.5") Baby Gemini 486SX-25 motherboard.

It is also known as the "Upgradeable" board because it can accommodate the Intel

OverDrive CPU. The part number for this board is 09-00145-xx.

It's identifying features are: an LED between expansion slots #5 and #6; eight 16-bit

expansion slots; four sockets for SIMMs (using 72-pin SIMMs); one proprietary 80-pin

SIMM socket which accommodates a Micronics External Cache Card.

The bus speed for this motherboard is fixed at 8MHz.

+=============================+

+ MOTHERBOARD SWITCH SETTINGS +

+ +

+ * = Default setting +

+=============================+

SW1

---

1 Memory size (see below)

2 Memory size (see below)

3 Memory size (see below)

4 Memory size (see below)

5 Reserved *Off

6 Reserved *Off

7 Reserved *Off

8 Reserved *On

DIP switch settings for memory size

===================================

Memory Banks DIP Switch 2

-----------------------------------------------

MB 0 1 2 3 S1 S2 S3 S4

---- ---- ---- ---- ---- ---- ---- ---- ----

4MB 4M ON ON ON ON

8MB 4M 4M OFF ON ON ON

12MB 4M 4M 4M ON OFF ON ON

16MB 4M 4M 4M 4M OFF OFF ON ON

16MB 16M ON ON OFF ON

20MB 4M 16M ON ON OFF OFF

24MB 4M 4M 16M ON OFF ON OFF

28MB 4M 4M 4M 16M OFF ON ON OFF

32MB 16M 16M OFF ON OFF ON

36MB 4M 16M 16M ON OFF OFF OFF

40MB 4M 4M 16M 16M OFF OFF ON OFF

48MB 16M 16M 16M ON OFF OFF ON

52MB 4M 16M 16M 16M OFF OFF OFF OFF

64MB 16M 16M 16M 16M OFF OFF OFF ON

In the table above, 4M indicates that one 1Mx36 SIMM is installed in the socket,

16M indicates that one 4Mx36 SIMM is installed in the socket. The above shows all

of the possible memory configurations.

When installing more than 16MB of memory, BIOS relocation must be disabled. Bios

relocation copies the video Bios (C0000-C7FFF) and the system ROM Bios (F0000-FFFFF) into

RAM. The motherboard adds 15MB to these addresses (F00000) to be able to differentiate

between the ROM and RAM. Enabling the relocation feature causes the memory above 16MB

to become non-contiguous and therefore inaccessible.

Micronics Computers has tested and verified the following 1Mx36 memory brands:

Micron Technologies, Mitsubishi, Samsung, Texas Instruments, Toshiba

Micronics Computers has tested and verified the following 4Mx36 memory brands:

Mitsubishi, Samsung, Toshiba

+=============================+

+ MOTHERBOARD JUMPER SETTINGS +

+=============================+

J5 External 6-volt battery connector

Pin 1 - Battery Positive

Pin 2 - no connector

Pin 3 - Ground

Pin 4 - Ground

J7 Keylock / Power LED

Pin 1 - Power LED signal

Pin 2 - no connector

Pin 3 - Ground

Pin 4 - Keyboard lock signal

Pin 5 - Ground

J8 External speaker

Pin 1 - Speaker

Pin 2 - no connector

Pin 3 - Ground

Pin 4 - +5 volts DC

W1 Turbo LED

Pin 1 - Signal

Pin 2 - Ground

W2 Reset switch

Pin 1 - Signal

Pin 2 - Ground

W3 Turbo switch

Pin 1 - Signal

Pin 2 - Ground