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TURBO MAIN BOARD (426A)

UNIDENTIFIED

TURBO MAIN BOARD (426A)

Processor

8088

Processor Speed

4.77/8MHz

Chip Set

Unidentified

Video Chip Set

None

Maximum Onboard Memory

640KB

Maximum Video Memory

None

Cache

None

BIOS

Unidentified

Dimensions

330mm x 218mm

I/O Options

None

NPU Options

8087

CONNECTIONS

Purpose

Location

Purpose

Location

Turbo switch (to turbo switch button)

JP5

Power LED

JP9 pins 3 & 4

Turbo LED

JP9 pins 1 & 2

Speaker

P4

USER CONFIGURABLE SETTINGS

Function

Label

Position

Factory configured - do not alter

JP1

Unidentified

 

Turbo enabled

JP6

Closed

 

Turbo disabled

JP6

Open

 

Turbo enabled (CTRL, ALT, +)

JP7

Closed

 

Turbo disabled (CTRL, ALT, -)

JP7

Open

 

Keyboard lock disabled

JP8

Closed

 

Keyboard lock enabled

JP8

Open

Factory configured - do not alter

SW1/1

Off

 

NPU not installed

SW1/2

On

 

NPU installed

SW1/2

Off

Note: JP6 is for turbo selectable through hardware. JP7 is for turbo selectable through software. Both jumpers cannot be closed at the same time.

DRAM CONFIGURATION

Size

Bank 0

Bank 1

Bank 2

Bank 3

256KB (A)

(9) 4164

(9) 4164

(9) 4164

(9) 4164

256KB (B)

(9) 41256

None

None

None

512KB

(9) 41256

(9) 41256

None

None

640KB

(9) 41256

(9) 41256

(9) 4164

(9) 4164

Note: The location of banks 0, 1, 2, & 3 are unidentified.

DRAM JUMPER CONFIGURATION

Size

JP3

JP4

256KB (A)

Pins 1 & 3, 5 & 7 closed

Pins 2 & 4 closed

256KB (B)

Pins 2 & 4, 6 & 8 closed

Pins 1 & 3 closed

512KB

Pins 2 & 4, 6 & 8 closed

Pins 1 & 3 closed

640KB

Pins 2 & 4, 6 & 8 closed

Pins 1 & 3 closed

DRAM SWITCH CONFIGURATION

Size

SW1/3

SW1/4

128KB

Off

On

192KB

On

Off

256KB

Off

Off

FLOPPY DRIVE SELECTION

Drives installed

SW1/7

SW1/8

1

On

On

2

Off

On

3

On

Off

4

Off

Off

MONITOR SELECTION

Type

SW1/5

SW1/6

None

On

On

Color (40 x 20)

Off

On

Color (80 x 25)

On

Off

Monochrome

Off

Off