Sonnet eGFX Breakaway Box Thunderbolt 3 graphics card enclosures shipping in late June for $299

Sonnet, the supplier of Thunderbolt 3 GPU enclosures Apple is providing to developers as part of an External Graphics Development Kit, is preparing to ship the eGFX Breakaway Box used in the kit to consumers from next month, giving end users a way to increase the graphical power of their iMac and MacBooks.

The eGFX Breakaway Box is a Thunderbolt 3-to-PCIe expansion chassis, equipped with a single slot for attaching a compatible PCIe card, including high-performance graphics cards. Measuring 7.25 by 8 by 13.38 inches and weighing 7.1 pounds excluding a GPU, the enclosure is able to fit a single full-length, full-height, double-width PCIe card.

Two versions will be offered to consumers, with the eGFX Breakaway Box 350 including one 8-pin and one 6-pin auxiliary power connectors, and a 350-Watt power supply capable of supporting cards requiring 300 Watts of power or less, and up to 15 Watts of upstream power. The 550 model houses a 550-Watt power supply, capable of driving cards requiring over 375 Watts of power with dual 8-pin aux power connectors, and offering 87 Watts of upstream power for charging a connected MacBook Pro.

Aside from the connections included with any installed card, the enclosure has only one Thunderbolt 3 USB-C port to connect it to the host system, with no option to daisy-chain other hardware over Thunderbolt 3 or to attach accessories using USB ports. This limitation effectively allows the installed graphics card full use of the 40Gb/s of bandwidth Thunderbolt 3 provides, without sharing it with other devices.

Sonnet claims the eGFX Breakaway Box is Thunderbolt-certified for both Mac and Windows. For Mac, it requires a Thunderbolt 3 connection, though it will also work with Thunderbolt and Thunderbolt 2 ports with adaptors, and though it claims to work with macOS 10.12.5 or later, Apple will not be officially supporting Thunderbolt 3 eGPUs until Spring 2018, under macOS High Sierra.

The enclosures will be able to support a wide array of AMD and Nvidia graphic cards, including some in the GeForce GTX 1000 and 900 families, and the Radeon RX 500, 400, and R9 product groups. Though the 550 model enclosure will work with the vast majority of cards, the lower capacity of the 350 unit will require owners to be choose a graphics card with more conservative power requirements.

Sonnet is expecting to ship the eGFX Breakaway Box 350 in early July for $299, with the 550 model available in the third quarter for $349. In both cases, users will have to supply their own graphics cards.

Apple's External Graphics Development Kit, which has started to ship to developers, uses the 350 model of Breakaway Box and also includes an AMD Radeon RX 580 8-gigabyte graphic card, a Belkin USB-C to 4-Port USB-A hub, and a promo code for $100 towards the purchase of an HTC Vive VR headset. The bundle, offered only to developers, is priced at $599.