[Updated Jan. 24, 2005] — Octagon Systems has devised a smaller, potentially more cost-effective scheme for expanding PC/104-compatible embedded systems, and has begun manufacturing products to the associated “XBLOK” specification. The tiny modules measure 1.65 x 3.55 inches — less than half the size of standard PC/104 modules — and can implement any of three different PC/104-defined buses, as illustrated below.

XBLOK modules can be built three ways — with a 8-bit ISA bus (left), a 16-bit ISA bus (center), or a 32-bt PCI bus (right).

According to Octagon, the smaller size of XBLOKs permits two expansion modules, such as Ethernet and digital I/O, to be plugged onto a single PC/104 stack location, while only increasing stack height by 0.6 inches (adding two full-sized PC/104 expansion modules would add 1.2 inches to the stack).

Additionally, when two XBLOKs are plugged onto a single PC/104 stack location, there is a 0.75-inch gap between them as shown below, through which heat can be dissapated from the carrier board — a possible benefit in systems with higher-powered processors located below the PC/104 stack. (Note: this scenario requires that one of the XBLOKs be PCI-bus interfaced, while the other is ISA-bus interfaced.)

When an ISA and a PCI XBLOK module are stacked on the same level (in a PC/104-Plus expansion location), there is a gap between them through which heat from below can dissipate.

Octagon has applied for a patent on the XBLOK concept that covers “all fractional versions of PC/104, PC/104+, etc. and is believed general enough to completely encapsulate the idea,” according to CEO John McKown. The company plans to license the patent to other board makers in a “straightforward” manner, but has not finalized the licensing terms, he adds.

Octagon says it has already developed a family of the mini XBLOK expansion modules (shown below), which currently includes: 10/100 megabit Ethernet (photo), quad-USB 2.0, digital I/O, dual-serial, and a battery-backed SRAM disk. The modules range in price from $60 to $104, and are rated for -40 to +85 degrees C operation.

Octagon's first family of XBLOK modules
(Click above image to enlarge)

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