Processor	80486SX/80487SX/80486DX
Processor Speed	20/25/33/50MHz
Chip Set	OPTI
Max. Onboard DRAM	256MB
Cache	64/128/256/512KB
BIOS	AMI/Phoenix
Dimensions	309mm x 331mm
I/O Options	None
NPU Options	4167

CONNECTIONS
Purpose	Location	Purpose	Location
Speaker	J4	Turbo LED	J6
Power LED & Keylock	J5	Reset switch	S9

USER CONFIGURABLE SETTINGS
Function		Jumper	Position
»	External BCLK buffering 486DX (33/50MHz)	JP1	pins 1 & 2 closed
	External BCLK buffering 486SX (20/25MHz) / 487SX	JP1	pins 2 & 3 closed
»	Snooping/Flush 20MHz CPU	JP8	closed
	Snooping/Flush 25/33/40/50 MHz CPU	JP8	open
»	Monitor type select monochrome	JP9	open
	Monitor type select color	JP9	closed
»	CPU speed select OSC/1	JP12	pins 1 & 2 closed
	CPU speed select OSC/2	JP12	pins 2 & 3 closed
»	RTC/CMOS type select DS1287/1287A	JP13, JP14 & JP15	pins 1 & 2 closed
	RTC/CMOS type select DS1387/1488	JP13, JP14 & JP15	pins 2 & 3 closed

DRAM CONFIGURATION
Size	Bank 0	Bank 1	Bank 2	Bank 3
4MB	(4) 1M x 9	NONE	NONE	NONE
8MB	(4) 1M x 9	(4) 1M x 9	NONE	NONE
12MB	(4) 1M x 9	(4) 1M x 9	(4) 1M x 9	NONE
16MB	(4) 1M x 9	(4) 1M x 9	(4) 1M x 9	(4) 1M x 9
16MB	(4) 4M x 9	NONE	NONE	NONE
20MB	(4) 1M x 9	(4) 4M x 9	NONE	NONE
24MB	(4) 1M x 9	(4) 1M x 9	(4) 4M x 9	NONE
28MB	(4) 1M x 9	(4) 1M x 9	(4) 4M x 9	(4) 1M x 9
32MB	(4) 4M x 9	(4) 4M x 9	NONE	NONE
36MB	(4) 1M x 9	(4) 4M x 9	(4) 4M x 9	NONE
40MB	(4) 1M x 9	(4) 1M x 9	(4) 4M x 9	(4) 4M x 9
48MB	(4) 4M x 9	(4) 4M x 9	(4) 4M x 9	NONE
52MB	(4) 1M x 9	(4) 4M x 9	(4) 4M x 9	(4) 4M x 9
64MB	(4) 4M x 9	(4) 4M x 9	(4) 4M x 9	(4) 4M x 9
64MB	(4) 16M x 9	NONE	NONE	NONE
128MB	(4) 16M x 9	(4) 16M x 9	NONE	NONE
192MB	(4) 16M x 9	(4) 16M x 9	(4) 16M x 9	NONE
256MB	(4) 16M x 9	(4) 16M x 9	(4) 16M x 9	(4) 16M x 9

CACHE CONFIGURATION
Size	Bank 0	Bank 1
64KB	(4) 8K x 8	(4) 8K x 8
128KB	(4) 32K x 8	NONE
256KB	(4) 32K x 8	(4) 32K x 8
512KB	(4) 128K x 8	NONE

CACHE TAG CONFIGURATION
Size	U54	U55	U56	U71	U72 (Dirty bit)
64KB	(1) 64K x 1	(1) 8K x 1	NONE	(1) 64K x 1	(1) 16K x 1 or (1) 64K x 1
128KB	(1) 64K x 1	(1) 8K x 1	NONE	(1) 64K x 1	(1) 16K x 1 or (1) 64K x 1
256KB	(1) 64K x 1	(1) 8K x 1	(1) 8K x 1	(1) 64K x 1	(1) 16K x 1 or (1) 64K x 1
512KB	(1) 64K x 1	(1) 32K x 1	NONE	(1) 64K x 1	(1) 64K x 1

CACHE JUMPER CONFIGURATION
Size	JP2	JP3	JP4	JP5	JP16	JP17	JP18
64KB	2 & 3	Open	Open	Open	Open	Open	Open
128KB	1 & 2	Closed	Open	Open	Closed	Open	Open
256KB	2 & 3	Closed	Closed	Open	Closed	Open	Closed
512KB	1 & 2	Closed	Closed	Closed	Closed	Closed	Closed
Note: Pins designated should be in the closed position.

CPU TYPE CONFIGURATION
Type	J10	J11
80486SX	pins 2 & 3 closed	open
80487SX	pins 1 & 2 and 3 & 4 closed	pins 1 & 2 closed
80486DX	pins 1 & 2 and 3 & 4 closed	pins 2 & 3 closed

EBC SPEED CONFIGURATION
Size	JP6	JP7
20MHz	Open	Open
25MHz	Open	Open
33MHz	Open	Closed
40MHz	Closed	Open
50MHz	Closed	Closed