User Guide

Frequently Asked Questions
B-4
A: The DoC is new certification standard of FCC regulations. This new standard
allows DIY component (such as mainboard) to apply DoC label separately
without a shielding of housing. The rule to test mainboard for DoC is to remove
housing and test it with regulation 47 CFR 15.31. The DoC test of mainboard is
more difficult than traditional FCC test. If the mainboard passes DoC test, that
means it has very low EMI radiation and you can use any kind of housing (even
paper housing). Following is an example of DoC label. Currently, AOpen
AX65/AP57/AP5T/AX5T had passed DoC test.
AX5T
Test To Comply
With FCC Standards
FOR HOME OR OFFICE USE
Q: What is PBSRAM (Pipelined Burst SRAM)?
A: For Pentium CPU, the Burst means reading four QWord (Quad-word, 4x16 = 64
bits) continuously with only the first address decoded by SRAM. The PBSRAM
will automatically send the remaining three QWord to CPU according to
predefined sequence. The normal address decoding time for SRAM is 2 to 3
clocks. This makes the CPU data read timing of four QWord to be at least 3-
2-2-2 and a total of 9 clocks if traditional asynchronous SRAM is used.
However, with PBSRAM, there is no need to decode address for rest three
Qword. Therefore, data read timing can be 3-1-1-1, that is equivalent to 6
clocks and is faster than asynchronous SRAM.
Q: What is EDO (Extended Data Output) memory?
A: The EDO DRAM technology of EDO is actually very similar to FPM (Fast Page
Mode). Unlike traditional FPM that tri-states the memory output data to start the
pre-charge activity, EDO DRAM holds the memory data valid until the next
memory access cycle, that is similar to pipeline effect and reduces one clock
state.
Q: What is SDRAM (Synchronous DRAM)?
A: The SDRAM is a new generation DRAM technology that allows DRAM to use
the same clock as the CPU host bus (EDO and FPM are asynchronous and do
not have clock signal). The idea is the same as "Burst" (refer to the previous Q
& A). It requires only one clock for the 2nd, 3rd, and 4th QWord (for example,
5-1-1-1 compares with EDO 5-2-2-2). The SDRAM comes in 64-bit 168-pin
DIMM (Dual-in-line Memory Module) and operates at 3.3V. Note that some old
DIMMs are made by FPM/EDO and only operate at 5V. Do not confuse them