About two week ago I purchased a used Z420 with the 'old' Boot Block Date of 12/28/2011. I have been doing a little reasearch into getting the boot block date updated to 2013 to support the Ivy Bridge CPU's and this thread makes for some interesting reading, since its a common theme for Z420/620/820 machines. I thought I'd share some preliminary findings in the hope of i) kickstarting the discussion off again ii) complementing / clarifing the information already present in this thread, since IMHO there are a few bits and pieces of information which were not mentioned here outright, but which could help resolve this, without the need for desoldering / reprograming the BIOS chip with an external programmer.
First thing is that there is no point looking for older bios versions in the hope that they change the boot block date during flashing - the new boot block date is contained in all subsequent bios versions (I am on the latest 3.90 Rev.A 8 Aug 2016). It can be seen near the end of the bios file when viewed with a hex editor.
The problem is of course that the boot block does not get updated during flashing. I have tried to look into this, by creating a bootable USB disk with FreeDos and using the Intel Flash Programming Tool (FPT) from the command prompt.
FPT correctly identifies the bios chip in the Z420 as a Winbond 25Q128BVFG. It also shows that the Boot Block region of the BIOS (0xFF0000 - 0xFFFFFF) is read / write locked. So removing this lock would allow us to flash this region of the bios, either via FPT or perhaps even using the original HP bios flashing utility.
The locks are contained in the Descriptor section of the Bios. Dumping the contents of the Descriptor to a file, modifing it and reflashing would allow for unlocking of the Bios and allow us to execute a full flash, including of the boot block.
I was pretty excited when I was able to dump the Descriptor section from my bios using FPT to a file desc.bin (fpt.exe -desc -d desc.bios). The result is a 4kb file. Then, using Intel Flash Image Tool (FITC) I edited Decriptor Region \ Master Access Section to remove the read / write locks. A problem however arouse on the last hurdle - flashing back the modified descriptor to the bios (fpt -desc -f desc.bin) as FPT reports that 'host CPU does not have write access to the target flash region'. It suggests modifing the descriptor settings (clearly just tried that with no success) to give host access to this region.
On some motherboards there are jumpers to unlock the Descriptor of the bios, other boards can be put into debug mode which allows the Decriptor to be changed. More likely than not there is some way of forcing the Zx20 boards into such mode.
This is pretty much all I got for the timebeing. Will be looking into this some more, in the meantime if any one has any other news or developments would be grateful if you could post this here.