On a modern system (Windows 7+, Linux wth GRUB 2.0 bootloader) all of the drawing is done without the VBIOS; the VBIOS is just used to set up the mode.
The VBIOS is a 16-bit x86 application, but it does not run on these systems in vm86; reason being that mode is not supported in 64-bit long mode.
When the VBIOS does execute, it never does from Flash. SBIOS copies into system memory first.
The Surface Book had an interesting narrative not only because of the hardware, but also the ironic underdog story of Microsoft vs Apple. Nevertheless Samsung gets plenty of coverage and discussion over new Galaxy S and Galaxy Note products and I bet they too would cause a stir if they launched a product like the Surface Book. Too bad they left the PC industry...
No, my Google-fu also failed me. There's also an SPI ROM that is an input into the DP-HDMI2 chip, so there's likely firmware there that is not part of Google's open-sourcing.
For what it's worth, this appears to be an active dongle using a MegaChips device to do the DisplayPort to HDMI 2.0 conversion. USB Type-C alternate mode handles the passing of DisplayPort audio/video data from the GPU over the USB pins (ML0-3), and the MegaChips device converts that to HDMI 2.0 TMDS signaling.
Apple is going for even higher margins, and it will still sell well since who doesn't want a lighter iPad?
* SoC: A5X was 165mm^2. A6X was 123mm^2. A7 is only 102mm^2 with a 64-bit memory interface instead of 128-bit. They can do PoP memory too for even smaller PCB area. So much cheaper.
* WiFi/LTE: same chips probably used on iPhone 5c, 5s, iPad Air, and iPad mini. Simpler inventory and buy in even higher quantities.
* Screen: same screen as all previous retina generations likely.
* Battery: much smaller since the GPU is more efficient. More cost savings.
Facebook joined the Linaro Enterprise Group (watched the announcement at ARM TechCon in Santa Clara last year), indicating that they are at least interested in developing that necessary server environment.
You're definitely right there is a large software maintenance cost, but that has to be weighed against any perf/watt savings (Anandtech's Calxeda review shows even early systems have potential http://www.anandtech.com/show/6757/calxedas-arm-server-teste...), being able to put pricing pressure on Intel, and not being tied to Intel as a single supply source.
The VBIOS is a 16-bit x86 application, but it does not run on these systems in vm86; reason being that mode is not supported in 64-bit long mode.
When the VBIOS does execute, it never does from Flash. SBIOS copies into system memory first.
Source: I’ve worked on VBIOS