MICRONICS MOTHERBOARD

80486SX-25 (Baby size 09-00093-xx)

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

The part number for this board is 09-00093-xx.

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

expansion slots; two 8-bit expansion slots; eight sockets for SIMMs (two banks of 4);

one proprietary 32-bit slot which accommodates the Micronics External Cache Card (see

below).

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

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

+ +

+ MOTHERBOARD SWITCH SETTINGS +

+ +

+ * = Default setting +

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

SW1

---

1 Reserved *Off

2 Reserved *Off

3 Reserved *Off

4 Reserved *Off

5 Reserved *Off

6 Reserved *Off

7 Reserved *Off

8 Reserved *Off

SW2

---

1 Memory size (see below)

2 Memory size (see below)

3 Memory size (see below)

4 Memory size (see below)

5 Memory size (see below)

6 Reserved *Off

7 Reserved *Off

8 CGA / EGA / VGA *On

Monochrome Off

DIP switch settings for memory size

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

Memory Banks DIP Switch 2

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

MB 0 1 S1 S2 S3 S4 S5

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

1MB 256K ON ON ON ON ON

2MB 256K 256K OFF ON ON ON ON

4MB 1MB ON ON OFF ON ON

5MB 256K 1MB ON ON OFF OFF ON

8MB 1MB 1MB OFF ON OFF ON ON

16MB 4MB ON ON OFF ON OFF

20MB 1MB 4MB ON ON OFF OFF OFF

32MB 4MB 4MB OFF ON OFF ON OFF

In the table above, 256K indicates that four 256Kx9 SIMMs are installed in the bank,

1MB indicates that four 1Mx9 SIMMs are installed in the bank, and 4MB indicates that

four 4Mx9 SIMMs are installed in the bank. The above shows all of the possible memory

configurations.

Please note that there are only two banks of memory. Each bank consists of four SIMMs,

and all four sockets within a bank must be filled.

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 memory brands:

Toshiba, Siemens, Mitsubishi, NEC

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

+ +

+ MOTHERBOARD JUMPER SETTINGS +

+ +

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

J19 External 6-volt battery connector

Pin 1 - Battery Positive

Pin 2 - no connector

Pin 3 - Ground

Pin 4 - Ground

J22 External speaker

Pin 1 - Speaker

Pin 2 - no connector

Pin 3 - Ground

Pin 4 - +5 volts DC

J23 Keylock / Power LED

Pin 1 - Power LED signal

Pin 2 - no connector

Pin 3 - Ground

Pin 4 - Keyboard lock signal

Pin 5 - Ground

W1 CPU type

Not installed - 486SX

Installed - 487SX

W2 CPU type

Not installed - 487SX

Installed - 486SX

W4 Reset switch

Pin 1 - Signal

Pin 2 - Ground

W5 Turbo switch

Pin 1 - Signal

Pin 2 - Ground

W6 Turbo LED

Pin 1 - Signal

Pin 2 - Ground

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

+ +

+ External Cache Card +

+ +

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

The External Cache Card allows the addition of 64K, 128K, or 256K of

external cache to the motherboard. It also provides a Weitek 4167

socket for a co-processor installation.

64K external cache

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

Install eight 8Kx8 SRAM chips into U1, U2, U5, U6, U9, U10, U14, and U15.

The chips must be 25ns or faster. Make sure that W1, W2, W3, and W4 on

the card are not jumpered.

128K external cache

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

Install four 32Kx8 SRAM chips into U1, U2, U5, and U6. The chips must be

25ns or faster. Make sure that W1, W2, and W3 on the card have jumper

blocks installed, and that W4 is not jumpered.

256K external cache

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

Install eight 32Kx8 SRAM chips into U1, U2, U5, U6, U9, U10, U14, and U15.

The chips must be 25ns or faster. Make sure that W1 on the card is not

jumpered, and that W2, W3, and W4 have jumper blocks installed.

After completing the cache installation on the card, insert the External

Cache Card into the special slot on the motherboard. To activate the cache,

set the External Cache feature to Enabled in the CMOS setup screen. Press

<Ctrl><Alt><Esc> after booting, then press <PgUp> to get to the second setup

screen. After setting the parameter, press <Esc> to save the settings and

reboot the system. If you press <F10> instead of <Esc>, the system will not

reboot, and the settings will not be saved.