Is anyone 100% sure that executing the 4,1 to 5,1 Firmware Update won't adversely effect ANYTHING regarding the 4,1 hardware once the firmware is implemented? I currently run a 4,1 Mac Pro 8-Core / duo 2.26MHz with 48GB mem (Tri-Channel configured) with a vB07 Boot. This machine presently runs Snow Leopard and will be configured to run a fresh install of El Capitan in a few shorts weeks. I do not plan on updating anything hardware related (aside from maybe graphics in the distant future) and not sure if the 5,1 firmware is forward optimized for only running what 5,1 machines had in them. I would hate to to do the firmware update and find my machine, for any reason, runs slower OR is effected more adversely in the future if I do install new hardware like new new graphics cards just because I am running a new firmware version not intended for the original machine build (board or whatever). I don't want to cause ANY issues but do want to take advantage of any more I can get out of my awesome 4,1 machine....it IS and HAS been running absolutely incredible for the past 7 years AS IS on Snow and I LOVE IT! What brought me to all this crap is now I have to finally bare down and upgrade the OS (going to El Capi) for simply 3 reasons at present: - The need to update my browsers (Safari and/or Firefox) moving forward - I'd like to finally be able to update my iPhone and iPad to the latest OS and still be able to sync my contacts & calendar - El Capi will supposedly run all my Adobe CS4 Apps with minimal to no issues (finally a newer OSX that will) If the 1st 2 above were not a concern I'd THANKFULLY and JOYOUSLY be running Snow till the pigs fly or until a new reason surfaced as a must for updating the software further. I have never in my life had a more flawless build than Snow and one that is so lighting fast...and that's without an SSD drive yet! To be frank I am pissed as all F@*&% that I have to do anything but as we all understand its the new Apple life we are now forever forced to mire in and we need to plan effectively to try and get the most out of what we have (incredibly huge investments) till its inevitable that we need to buy-into the NEW beast (without our past fearful leader behind us) or just make the move back to PC (UUUUGH!-PUKE I cringe at the thought of even just typing that). Sooooo...since I DO need to OS upgrade I am thinking it might be a good idea (???) to be ready for a FUTURE install of Sierra (or newer?) - hence the question of the firmware update NOW before we get locked out of anything that even surpass the download firmware check): 1) How can we be 100% sure there are absolutely no drawbacks to doing/running the third party firmware update with no effect related to the original 4,1 hardware? 2) Are there any concerns that the Firmware Tool application could have any malware qualities to it unbeknown to a rookie clueless like me? 3) Have enough people done this to qualify all that or is this still too new of a process to tell? 4) Has anyone done system bench-marking to determine any performance issues or glitches on a system that has gone from firmware 4,1 to 5,1 (without changing anything else)? *From most of what i read most people who perform the firmware update go right to the newer memory type (1333MHZ) and CPU upgrades (these I will NOT be doing at anytime - I'd only do the firmware update to get my hands on a fresh installer of Sierra for archiving before it ends up being too late). Thanks to all who took the time to read this post and for any help/insight you can offer.