UEFI and "Secure Boot" W510 and maybe W7xx


For several weeks now people have been trying to get any meaningfully information about changing the BIOS Boot mechanism from UEFI to Legacy. Just turning off "Secure Boot" seems to have no effect.


Before I start, more than you ever wanted to know can be found by  downloading the UEFI specification v2.3.1 from http://www.uefi.org/ and the tool from http://www.intel.com/content/www/us/en/architecture-and-technology/unified-extensible-firmware-interface/intel-uefi-development-kit-debugger-tool.html


OK from what I have seen UEFI recommends that manufacturers provide a "Legacy" mode, primarily for troubleshooting and diagnosis. In UEFI mode, only signed boot devices will be recognised. The problem is that for many, (like Windows 7) the only signed version are the 64 bit  and the Intel 2760 in the W510 only supports 32 bit. I saw the same reference on several Linux pages.


In fact the version of Windows 8 on one of my test machines loaded "Legacy" possibly because the BIOS is pre-UEFI.


Why can't the W510 BIOS be switched from UEFI to Legacy ? There are two theories: One has to do with the W510 being sold by the Microsoft store and mentioned specifically in some Intel items.


More likely the answer is power. One of the major elements of the Clover Trail (2760) is that it is very low power. In fact like the switch from 5W-30 to 5W-20 oil in cars to get another .01 MPG out (not sure why sine the EPA rounds up to the nearest MPG but...) the Clover Trail has many power saving features to extend the internal battery life.


At present only Windows 8 (Microsoft and Intel working together) fully supports these features of the chipset. Some have reported "throttling" on other Intel devices (e.g. I5) which is a crude form of power reduction. Excessive heat (another issue with sealed Tablets). In the old days this would continue until the system failed due to overtemp. Today's tablets have temperature sensors in various places (see Coretemp). Windows 8 can respond to impending overtemp by reducing power to various components or to should down entirely if exceeded. Other operating systems have only limited capability but this is what enables a CloverTrail to run normally at 1.8 GHz instead of 1.5.


Now if the device were allowed to run Windows 7 or Ubuntu "Live", it is possible that power/heat capacity could be exceeded with nasty effects on warranty claims. An easy was t prevent this is to allow only UEFI signed operating systems and further limit them to only ones that can comply with the Clover Trail limits.


So my personal suspicion (am sure will be corrected if rong) is that the W510 is right on the limit of both thermal and power capacity and must be able to be throttled back by the OS when needed. Right now, Win 8 is the only OS that can do this. This is why I am using a powered USB hub and have suggested that some CD/DVD issues might be power related.


Personally think we should be amazed and appreciative that this is even possible (and the 7" form factor designs I expect next will be even more so) but then I tend to take a long view. It would just be nice for Acer to either admit to what is going on or demonstrate that I am full of it. Either is possible. But for people used to being on the bleeding edge, Mushroom management does not work.


BTW http://www.anandtech.com/show/6529/busting-the-x86-power-myth-indepth-clover-trail-power-analysis make a very interesting read with a picture of an open W510.


ps We now know how to make a flash drive "recovery disk" from the System DVD disk. You need to load into a PC as an .ISO file and make a bootable Flash drive (I use an 8 GB class 10) formatted as Fat32 (and not NTFS). Not difficult once you know how.





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