Expanding on the palm-sized ODroid-X Exynos-based platform released in July for $129, Hardkernel has unveiled three additional packages for developers and hobbyists. Said to be the world's smallest and most cost effective quad-core ARM PC, Hardkernel's $69 ODroid-U appears to offer similar specs to the ODroid-X, despite having a much smaller body at 48 x 52mm (roughly 1.9 x 2.0in) versus 90 x 94mm.

The ODroid-U is powered by a 1.4GHz Samsung Exynos 4412, which includes a quad-core Cortex A9 CPU with 1MB of L2 cache and a 400MHz Mali 400 GPU that supports 1080p video playback via micro HDMI. For another $20, Hardkernel offers the upgraded ODroid-U2, which has a 1.7GHz CPU, 440MHz GPU and doubles the system memory from 1GB to 2GB, but is otherwise identical to the cheaper ODroid-U.

Both of those models carry a 10/10Mb/s Ethernet jack, two USB ports, a microSD card slot, an eMMC module socket, as well as audio output via HDMI and a standard 3.5mm headphone jack. They're also offered with various optional add-ons, including a $12 Realtek USB 2.0 Wi-Fi dongle. Interestingly, the base price includes a small (59 x 57 x 60mm) black aluminum chassis that doubles as a heatsink.

Along with the ODroid-U and U2, Hardkernel has unveiled a more direct update to the original ODroid-X, fittingly dubbed the ODroid-X2. Priced at $135, the X2 carries the same 1.7GHz/440MHz Exynos SoC and 2GB of RAM found in the U2, except its 90 x 94mm body is used to deliver six USB ports, a full size SDHC card reader and a 50-pin IO port. It doesn't ship with a case, but it does have a passive heatsink.

All three systems can run Android as well as Ubuntu and other Linux distributions. Of note, unless you have a compatible power adapter and a spare microSD card, you'll have to spend another $20 or so to get going (Hardkernel sells an 8GB microSD card with Android 4.x preinstalled for $13). Initial shipments of the ODroid-U and U2 are on track for early January, while the ODroid-X2 is due sometime this month.