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PB88 Motherboard Layout

Backplane

CN1 (PARALLEL) CN2 (SERIAL)(POWER LED)

CPU Board:
256K_ (KEYBOARD) (SPEAKER)

Piggy Back 8087
Note This board plugs in on the CPU board into the Math co-processor socket (U43).

Sockets

1. BACKPLANE

Socket	Chip	Description
U8	8250	I/O
U29	765AC-2
U30	58167	Real Time Clock (RTC)
BAT		Battery Soldered

2. CPU CARD

Socket	Chip	Description
U16	8255A-5	Programmable Peripheral Interface
U24	8237A-5	DMA Controller
U25		BIOS
U29	8253-5	Programmable Interval Timer
U42	8088-2	Processor
U43	8087-2	Math Coprocessor/Piggy back board (optional)
U44	8288	System Controller and Bus Driver
U52	8284A	Clock Generator
U54	8259A-2	Programmable Interrupt Controller

3. PIGGY BACK 8087

Socket	Chip	Description
U1	8087	Math Co-processor (Optional)

Jumpers/Switches

1. JUMPERS
Note: This system does not have any Jumpers.

2. DIP SWITCHES:
CPU Board:
EXAMPLE:

Test OFF -- -- -- -- -- -- --
Math Coprocessor S1 S2 S3 S4 S5 S6 S7 S8
Not Installed -- ON -- -- -- -- -- --
Installed -- OFF -- -- -- -- -- --
No Function S1 S2 S3 S4 S5 S6 S7 S8
No Function -- -- OFF OFF -- -- -- --
Graphics S1 S2 S3 S4 S5 S6 S7 S8
Low Resolution -- -- -- -- OFF ON -- --
High Resolution -- -- -- -- ON OFF -- --
Monochrome -- -- -- -- OFF OFF -- --
Diskette Select S1 S2 S3 S4 S5 S6 S7 S8
    1 Floppy Drive -- -- -- -- -- -- ON ON
    2 Floppy Drives -- -- -- -- -- -- ON OFF

Video Card
Note The DIP Switch is located on the metal bracket on the Video Card.
Monitor Emulation S1 S2 S3 S4 S5 S6 S7 S8
Monochrome ON -- -- -- -- -- -- --
CGA OFF -- -- -- -- -- -- --
Monitor Type S1 S2 S3 S4 S5 S6 S7 S8
TTL Monochrome -- OFF ON OFF OFF ON -- --
CGA Color -- ON OFF ON OFF ON -- --
Composite Mono -- ON OFF ON OFF ON -- --
Composite Color -- ON OFF ON ON ON -- --

RESERVED S1 S2 S3 S4 S5 S6 S7 S8
Reserved -- -- -- -- -- -- ON ON

Connectors