Does a 3680 require a 1000W power supply for an I7-14700K to post?

It looks as though Dell consider a 1KW PSU mandatory for the 14700k

Dell UK offers the basic i7-14700 with as little as a 500w PSU. While it doesn't appear possible to spec a 3680 with the 14700k on the UK site (at the moment), it is still possible on other Dell sites and if you do so, e.g. on the Australian site, the 14700k is only available with a 1000W PSU

https://www.dell.com/en-au/shop/dell-desktop-computers/precision-3680-tower/spd/precision-t3680-workstation/on3680wt02au

In addition, if you look for 3860 Towers with the i7-14700k in the UK, they all seem to have the 1KW PSU.

e.g.

https://uk.insight.com/en_GB/shop/product/R7X8R/DELL/R7X8R/Dell-Precision-3680---Tower-Workstation---Intel-Core-i7-14700K---32-GB-RAM---1-TB-SSD/

https://www.misco.co.uk/product/Computers/Workstations/Dell/Dell-Precision-3680---performance-tower-Core-i7-i7?prodid=9481333&info=9

Apologies for repeating myself, I thought the first reply had been lost as it disappeared - so I reposted :-) 

The I7-14700K is only 125w.  500w PSU should suffice depending on the GPU card.  May be a dud CPU?

The 'base power' demand for the i7-14700K may be 125W but the maximum power draw is 253W when in full-fat turbo-nutter mode (likely to be entered as part of the POST) 

Along with this, the majority of components are likely to draw maximum power rating during boot, and they'll all be doing its at once - we don't know the full config of the system but PSUs rarely have to supply as much power as they do during initial power-up.

The OP quotes and 'ASF2-Force Off' log entry. This indicates an issue with power delivery, Dell even say that 'In some cases, the error is related to TurboBoost, which overstrains the system's power delivery'.

If the OP still has access to the 750W supply, I'd be tempted to strip back the machine to bare essentials - use a single low-power GPU, remove any other add-in cards, disconnect power to any HDD etc. and then try the 14700k again.

Since my previous post, it's occurred to me that it might not be as  simple as trying to reduce the power draw to a certain level to get the system to boot.

As Dell don't know what additional upgrades the system might receive, they have to allow for worst-case scenarios and as a 14700k with a GeForce 5090 could easily result in a power draw of over 800w a 1000w PSU would be regarded as the minimum required.

To enforce this, it's quite possible that the Dell BIOS has a table with the minimum PSU requirements for each supported CPU, if the PSU is under that requirement, the system refuses to boot.

To enforce this, it's quite possible that the Dell BIOS has a table with the minimum PSU requirements for each supported CPU, if the PSU is under that requirement, the system refuses to boot.

Thanks for the input. Dell do seem to make things as difficult as possible. I upgraded a 3660 from 300W PSU to 500W - no other changes -  and the BIOS then demanded I fit front case fans with no way of disabling the error. However, at least in that situation you could just accept the error and continue to boot. 

With the 14700K it won't even post.

I'm going to try and borrow a Z790 motherboard so I can test the chip. Assuming that is all OK then it must be the 1000W PSU.

The answer is 'Yes, the i7-14700k requires a 1000w PSU' (and 'premium cooling')

I found the 3680 Technical Guidebook at

https://www.delltechnologies.com/asset/en-us/products/workstations/technical-support/precision-3680-tower-technical-guidebook.pdf

If you look at the supported processor matrix at the bottom of p.10 there is a note at the bottom that states

Precision 3680 Tower supports Unlimited Turbo Duration feature (PL1=PL2) for all K-processor (125W) CPUs. A 1000W power supply and Premium Air Cooling solution are required.