Specifications

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Table 2-5. Onboard DRAM Memory Size Jumpering
SIMM
QTY.
SIMM
TYPE
LOCATION W3 W4 W5 SYSTEM
MEMORY
EXTENDED
MEMORY
2 256K U1,2 open short short 512K 0K
4 256K U1,2,3,4 short open short 640K 0K
4 256K U1,2,3,4 open short short 640K 384K
2 1M U1,2 short short open 512K 0K
2 1M U1,2 open short open 640K 0K
2 1M U1,2 short open open 640K 1408K
4 1M U1,2,3,4 open open open 640K 3456K
On a 12MHz system, use 120 nS (or faster) SIMMs. On a 16MHz system, use 100 nS (or faster)
SIMMs.
An additional set of six jumpers (W10, W11, W14-W17) is factory set according to both the
board's CPU clock rate and the DRAM memory's access time requirement. These are factory
settings, and should not be altered.
2.3.3 Math Coprocessor
Signals for interfacing with a standard 80287/80C287 floating point coprocessor are provided at
J11, which is identical in pinout with the normal 40-pin DIP socket, but on .1" row-to-row
spacing. An 80287/80C287 Carrier assembly, available from Ampro, allows you to install a
80287 math coprocessor at this location.
The required speed of the 80287/80C287 math coprocessor is 2/3 the clock rate of the CPU.
Therefore the 12 MHz Little Board/286 requires an 8 MHz device (80287-8), while the 16 MHz
board requires a 10 MHz device (80287-10).
Note
Be sure to install the 80287 on the 80287 Carrier with the IC's
pin 1 correctly positioned in pin 1 of the IC socket; be sure to
install the 80287 Carrier on the Little Board/286 so that it
overlaps the board (pin 1 of J11 mates with 80287 Carrier
socket receptacle 1).
When installed on J11, the 80287 math coprocessor is compatible with that of a standard AT
computer in all operational details.
Note
The NMOS 80287 math coprocessor generates a large amount
of heat relative to that produced by the Little Board/286 itself.
Be sure to provide adequate clearance and air flow in the
vicinity of the math coprocessor if the NMOS device is used.