This document is for the baby-sized (13.3" x 8.5") Gemini VL-Bus motherboard.
The part number for this board is 09-00144-xx.
It's identifying features are: an LED between expansion slots #5 and #6; six 16-bit
expansion slots; two 16-bit/VL-Bus expansion slots; four sockets for SIMMs; a socket
for an OverDrive CPU; two IDE interface connectors; one floppy connector; two serial
port connectors; one parallel port connector.
The ISA bus speed for this motherboard is fixed at 8MHz. The VL-Bus bus speed is
determined by the CPU speed. If the CPU is a 486SX-25, or 486DX2-50, the VL-Bus
bus speed is 25MHz. If the CPU is a 486SX-33, 486DX-33, or 486DX2-66, the VL-Bus
bus speed is 33MHz.
+=============================+
+ +
+ 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 CPU selection (see below)
6 CPU selection (see below)
7 CPU selection (see below)
8 CPU selection (see below)
DIP switch settings for memory size
===================================
Memory Banks DIP Switch 1
-----------------------------------------------
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
DIP switch settings for CPU selection
=====================================
DIP Switch 1
---------------------
CPU Speed S5 S6 S7 S8
--------------------------------------
33MHz or 66MHz Off On Off Off
25MHz or 50MHz On Off On Off
+=============================+
+ +
+ MOTHERBOARD JUMPER SETTINGS +
+ +
+=============================+
J11 Com Port A
J12 Parallel Port
J14 Com Port B
J15 Floppy connector
J16 Primary IDE connector
J24 External 6-volt battery connector
Pin 1 - Battery Positive
Pin 2 - no connector
Pin 3 - Ground
Pin 4 - Ground
J28 External speaker
Pin 1 - Speaker
Pin 2 - no connector
Pin 3 - Ground
Pin 4 - +5 volts DC
J29 Keylock / Power LED
Pin 1 - Power LED signal
Pin 2 - no connector
Pin 3 - Ground
Pin 4 - Keyboard lock signal
Pin 5 - Ground
J30 Secondary IDE connector
W13 CPU selection
Pins 1-2 486DX, 486DX2
Pins 2-3 486SX
W15 Reset switch
Pin 1 - Signal
Pin 2 - Ground
W16 Parallel port I/O direction
Pins 1-2 Input mode
Pins 2-3 Output mode (default)
W17 Turbo LED
Pin 1 - Signal
Pin 2 - Ground
W18 Turbo switch
Pin 1 - Signal
Pin 2 - Ground
W19 IDE LED
Pin 1 - Signal
Pin 2 - Ground
W20 Flash ROM operation (see note below)
Pins 1-2 Recovery
Pins 2-3 Normal operation (default)
DO NOT change jumper W20 unless instructed by a Micronics Technical Support Engineer.
Changing the jumper will result in the Bios being erased. You must have a Flash
recovery floppy diskette before attempting to recover. The jumper is NOT moved when
updating the Flash ROM.
+==========================+
+ +
+ Additional Information +
+ +
+==========================+
I/O Port addresses
------------------
COM1 3F8h
COM2 2F8h
COM3 3E8h
COM4 2E8h
LPT1 3BCh
LPT2 378h
LPT3 278h
IRQ list
--------
IRQ 6 Floppy controller
IRQ 14 Primary IDE controller
IRQ 15 Secondary IDE controller
When using the on-board I/O ports, the interrupts used cannot be shared with
another device. IRQ14 and IRQ15 cannot be shared, regardless of whether or
not IDE drives are attached to the on-board connectors.