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19 BIOS Consideration
19.1 Legacy versus Legacy Free
For the purposes of this document, legacy refers to a set of peripherals provided in desktop PCs and
associated chipsets that are no longer in production, including PS/2 keyboard and mouse, parallel port
(LPT), and UART serial ports. The COM Express standard was created with newer chipsets in mind. As a
result, COM Express is legacy-free, which means that legacy peripherals are not directly supported by
the module. Such peripherals have been replaced by space-efficient high-speed interfaces such as
USB 2.0. To facilitate the market's transition toward newer peripherals, the low pin count (LPC)
interface was created as a space-efficient replacement for the Industry Standard Architecture (ISA) bus.
In addition to firmware devices such as BIOS flash, low-speed Super I/O controllers were developed for
the LPC bus to fill the gap until the momentum could build for new high-speed, serial-based
peripherals.
19.2 Carrier Super I/O Support
A carrier board Super I/O implementation usually requires BIOS customization to support the Super
I/O. If the carrier board uses the same Super I/O as the Emerson-recommended boards, then it may be
possible to use the standard legacy BIOS that goes with the particular module. One Super I/O that is
supported in the BIOS implementation for the COMX-ATOM-420 is the Winbond W83627THF. Check
the relevant user's guide with your Emerson FAE.
Page 88 of 103
COM Express Carrier Type 2
Design Guide
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