PROTEUS user manual
Issue C
34
Graphics support
The IGD (Integrated Graphics Device) provides LVDS and Serial DVO (SDVO) display
ports permitting simultaneous independent operation of two displays.
in the COM Express configuration SCH LVDS interface is connected directly to the
board-to-board COM Express connector and SDVO interface is connected via a Chrontel
CH7308B SDVO to LVDS converter to a edge connector. in the standalone configuration
two LVDS onboard connectors are used.
Bandwidth limitations
The ATOM chipset has been optimized for low power operation and therefore has some
limitations in terms of it’s data throughput capabilities. The internal bus architecture has a
maximum theoretical throughput of approximately 254MB/s. System IO devices are
interfaced to the US15W backbone, so if the PCI Express controller has control of the
backbone then no other devices are able to gain access.
The backbone does not allow peer-to-peer transactions, so if the incoming PCI Express
data is being transferred to the PATA port, then the two devices have to share the
backbone with PCI Express data being transferred to memory, and then from memory to
the PATA port. in some usage models for the PROTEUS, full data bandwidth of devices is
not available.
Main memory
The PROTEUS is populated with eight on-board 16-bit DDR-2 memory devices. The
COM Express specification lists a SODIMM implementation for adding memory whilst the
physical requirements for this are such that it limits the available area for wireless
expansion. A decision was made to support only soldered down memory components.
Both industrial and commercial temperature range memory components are available as
build options. These have a population option to run at either 400 MHz or 533 MHz. The
chipset supports only non-ECC memory.
The system memory is shared with the video memory and therefore limits the maximum
available system memory. The BIOS configuration allows for the default video memory
size to be specified.
BIOS ROM memory
The PROTEUS module incorporates a minimum of 4Mb of FLASH memory with a default
population of 8Mb of FLASH memory for support of the BIOS.
An external FWH, required by the COM Express specification, is supported and enabled
as a boot ROM device via control signals available on the COM Express board-to-board
connector.