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.