Specifications
Little Board/P5i Technical Manual
2–8
To connect the external battery to byte-wide socket S0 to back up an SRAM, install jumpers on W2 and
W21-2/3. If you use another type of memory device in S0, you must remove W2 and install a jumper on
W21-1/2.
2.2.4 Cooling Requirements
The Pentium CPU, DRAM SIMMs, video controller, and core logic chips draw most of the power and
generate most of the heat. The board is designed to support various speed versions of the Pentium from
100 MHz to 166 MHz with 66 MHz clocks. The standard models use a 3.3V CPU, and optional models
can be special-ordered with VRT (3.1V core) processors for use in power-sensitive applications. As CPU
speeds offered by manufacturers are continuing to increase, contact your Ampro sales representative for
the currently available speeds.
A heat sink and (optional) fan assembly are provided for the CPU. The fan gets its +5V power from J20.
Table 2-5 shows the maximum ambient temperature for a CPU case temperature of 70 °C at various
airflow values for various models of the Little Board/P5i. (Values for the 133 MHz VRT CPU are given
for an 85 °C CPU case temperature.)
Table 2–5 Airflow vs. Maximum Ambient Temperature
Processor Speed Still Air 200 LFM 400 LFM Fan/Heatsink
100 MHz Max
-5.8 30.6 49.8 54.9
100 MHz Typical
40.8 54.8 62.2 64.2
100 MHz Stop Grant
58.4 64.0 66.9 67.7
166 MHz Max
-24.5 20.9 44.8 51.1
166 MHz Typical
34.0 51.3 60.4 62.8
166 MHz Stop Grant
55.8 62.6 66.2 67.2
133 MHz* Max
25.8 54.2 69.2 73.2
133 MHz* Typical
55.0 69.4 77.0 79.0
133 MHz* Stop Grant
75.3 79.9 82.4 83.1
Thermal Resistance of a
Typical .65” Heat Sink and
Fan/Heatsink Combination
7.5 3.9 2.0 1.5
* VRT CPU
2.3 DRAM
The board has positions for two 72-pin Single In-line Memory Modules (SIMMs), U1 and U2. The
Pentium’s memory is organized as a 64-bit data bus, so you must use two modules, the size depending on
your memory needs. (Both SIMMs must be the same size and type.) The ROM BIOS automatically
detects the memory modules that are installed and configures the system accordingly.
You can use standard fast page-mode DRAMs or EDO DRAMs with access times of 70 nS or less. Either
32-bit or 36-bit SIMMs may be used.