I like to listen to march music. It might seem odd, but it’s fun. Recently, I discovered the works of Fred Jewell (Fig. 1), the Indiana March King. After a little research, I found that Jewell was on par with and a contemporary of the more famous John Philip Sousa.
About the same time as my research, Intel announced its Tunnel Creek Atom processor (Fig. 2). The chip is going to be smaller and faster than its predecessor, but that’s to be expected. It also moves the memory controller and the display controller, which used to reside in the System Controller Hub (SCH), into the main processor chip. The SCH chip is actually larger than the Atom processor. The combination is designed for lower-power applications but the SCH is a significant portion of that.
The SCH also provides a range of interfaces frequently found on laptops and PCs depending on the incarnation such as USB ports, PCI or PCI Express, SATA or PATA disk interfaces, plus audio support. This feature set can be overkill for many embedded applications, but developers usually don’t have a choice.
The SCH and Atom processors typically communicated via a fast front-side bus (FSB). The architectural approach is common to many of Intel’s chips. It tends to limit the options for the SCH.
PCI Express And SPI Make A Difference
Tunnel Creek replaces the FSB with four x1 PCI Express links. This is critical for embedded developers because PCI Express brings key advantages.
It’s still possible to build a chip like an SCH with a range of peripherals. The SCH simply connects to the Atom processor via PCI Express. The chip also becomes more useful since it could be used by any processor with a PCI Express port.
Further, it’s handy if multiple interfaces found on this SCH are needed because a second SCH could be connected to another PCI Express port. Likewise, PCI Express switches could be used to expand the number of connections the Atom processor could work with.
More interesting configurations occur when the SCH goes away or is optional since there are a number of chips with PCI Express interfaces. For example, if a pair of Gigabit Ethernet ports are required, then the Atom could handle them with a pair of PCI Express/Gigabit Ethernet chips. In many applications, a single PCI Express port may suffice to handle the application interface.
Likewise, creating a custom interface chip for the Atom is straightforward. Even hooking in an FPGA should be easy since PCI Express ports are standard fare in programmable hardware. This simplified interface can greatly reduce the bill of materials (BOM).
Another vital change includes the boot options and the serial peripheral interface (SPI) and low-pin-count (LPC) bus interface found on the Atom. These features enable an Atom to boot from an SPI serial flash memory chip to DRAM supported by the on-chip memory controller. This combination makes the new Atom very interesting for embedded developers.
Check out Intel if you need to use the latest Atom. And, check out the Brazil Concert Band’s Web site if you like march music. Matt Huber, the band director, introduced me to Jewell’s music.