Electronic Design

EPIC Express Rides The Rails

With the ink barely dry on the EPIC Express standard, Ampro delivers the Ready-Board 820, the first of possibly many EPIC Express products (Fig. 1). This Pentium M-based platform fits into the same space as the EPIC standard, but it swaps the large PC/104 Plus expansion connectors with a tiny PCI Express connector. Even so, a single PCI Express lane brings more bandwidth to the table than an entire PC/104 stack.

EPIC Express burst on the scene almost a year ago (see "More On EPIC Express"). Initially developed by a small group of PC/104 vendors, it's since been refined, and connectors have been developed to handle PCI Express speeds. The existing standard forgoes the PC/104 ISA bus for a stackable PCI Express expansion system, and the PC/104 Embedded Consortium has adopted it.

PCI Express is a point-to-point interconnect, whereas PC/104 has gone with an ISA or PCI bus. EPIC Express employs a staggered stacking architecture to distribute PCI Express links to expansion boards (Fig. 2). Unlike PC/104, the EPIC Express expansion boards use two surface-mount connectors, one on the bottom of the board and one on top.

The first PCI Express x1 lane is always routed to the expansion board's PCI Express device. The remaining lanes are routed from the bottom to the top connector. Shifting the PCI Express links means the first lane will always have a connection to the baseboard until the stack exceeds the number of lanes provided.

The ReadyBoard 820 implements the Standard connection with four x1 PCI Express lanes. The EPIC Express standard also supports a three-bank connector. This adds two x4 PCI Express lanes that move up the stack like the x1 links, except the x4 links are shifted together. The current stacking limit is two x4 boards and four x1 boards using the three-bank connector.

Also, the ReadyBoard 820 will support four x1 expansion boards. It has the usual complement of peripherals in addition to the EPIC Express expansion connection (see "ReadyBoard 820 Specifications"). And, it includes a pair of Ethernet ports—one for 1-Gbit/s Ethernet and the other for 10/100 Ethernet.

EPIC Express is now out of the starting gate. It will be interesting to see what expansion board options next become available.

EPIC Express
PC/104 Embedded Consortium

ReadyBoard 820 Specifications
CPU: 1.8-GHz Pentium M 745
Memory: 1-Gbyte DDR2 400 SO-DIMM
BIOS: AMI with APCI 2.0
Expansion: EPIC Express standard quad x1 connector; 3.55- by 3.75-in. expansion board
Peripherals: Dual Serial ATA, Ultra DMA 33/66/100 IDE with Compact Flash socket, floppy-disk interface, dual serial, parallel printer port, four USB 2.0, PS/2 keyboard/mouse, eight general-purpose I/O, AC 97 audio
Networking: 1-Gbit Ethernet port, 10/100 Ethernet port
Video: Intel GMA 900 2D/3D accelerator, CRT and Direct Broadcast Delivery System display interfaces, 3.3- and 5-V low-voltage differential-signaling support
Packaging: 4.5- by 6.5-in. board

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