iwer, stefacnt:
Thanks for your IRC help a couple days ago. I have been partially successful in using the ROM layout file  (-l) feature in flashrom to segment the writes to the flash in my HP Z820 workstation. It evident the HP Z820 flash has two ‘regions’: that below 0x510000 and that 0x510000 and above. The lower portion contains the coding for the Intel AMT/ME features and other data. The attached lower.txt file is log of the successful write flash addresses below 0x510000.
But writing to the space above 0x510000 is still a problem. In that space I tried writing just to the bootblock area (which is all I am seeking to update in this flash) and while flashrom tags it initially as read/write, the write fails. See the attached upper.txt logfile. I did attempt writing to the entire upper section (not just the bootblock) and got the same results.
The flash is hardware write enabled or I could not have written to the area below 0x510000. It seems something else seems needs enabling. Any thoughts would be helpful.
Thanks again ...