@diligentminds. Sorry i came over rude. But i took your post as 'instrument bashing without backup'.
The new machine does not aspire to be better than a 34401. Its goal is to be a 100% replacement for the aging 34401. Like i said the 34401 will disappear soon as they are running out of parts for it. Yet industry demands it. There are rpoblems plonking in a 34410 or 34411 instead of a 34401 as there are software incompatibilities ( sending 10nplc to a34410 is different dan 10nplc to a 34401. What is slow 61/2 on the 34401 is fast 61/2 on the 410... This gives problems. Also some of the other new machines have no more gpib. The new 6x has gpib (albeit an option).
It is purely designed as 100% code and function replacement.
So they are not going to put in ltz references as it is not needed. Nor does it need to ne more accurate than the 34401. As they will not alter the program code driving the testsetup the extra precision would be lost anyway. If the code is written to extract 51/2 digit in fast mode. It does no good to plonk in a machine that can doe 71/2 digit. The code only extracts 51/2 . So they dont want to pay for functionality that will not be accessed. Like i said: goal no1 of the machine is 100% compatibility. Sure they threw in some extra stuff that did not add to the bomcost. But adding an ltz style reference would have mandated higher cost. The twrget price was 34401 territory.
If you want better performance , faster reading, better tolerance they got other machines.
And by the way , the service manul IS up for the machine. No schematics though but there are some color pictures of the inside , some repair , replace tips and an explanation of how it does certain things.
I have it on good authority that we will see a replacement for the 3458 as well....