Precision 3620 will not work after cpu upgrade, help.

When upgrading processors, a BIOS firmware update will certainly helped.  But depending on the shipped date, BIOS firmware with supported microcode may already applied.  You can try to reset CMOS via jumper to see if new processor can be recognized.  Note that there is no overclocking option for K processor.

May need to reinstall previous CPU and update BIOS.  Then reinstall i7-7700k.

Make sure no pins are bent.  Also make sure old thermal paste didn't inadvertently get between CPU and socket.  It happened to me and I luckily had the impulse to double-check things before turning on.

Thank you for your help.

I have replaced the original cpu, monitor worked ok, reset CMOS now I have no video out put from my graphics card, on board HDMI or DP.

When it re booted, it seemed to go through a diagnostics set up but I can't see it.

I'm leaving it on for a few hours to see if it will turn the video back on after it's diagnostics. 

This is going from bad to worse

Try without the gpu.

Also, is the ram normal or ecc ? because if ecc, it will not let a normal cpu boot while the xeon will boot

Removed gpu, memory but nothing. Removed the button cel and re set cmos, nothing - then a bit later sprang into life. Had to do battle with the bios set up all over again. Forgot about raid setting, and legacy / uefi, all sata cables in the wrong holes   but it's back.

Memory not ecc, bios=1.2.4 anyone know if this old bios is ok with a i7-7700k ?

Thank you for your help.

probably the bios is a bit old , they moved to version 2.x since 2017

Latest BIOS for the 3620 is 2.25.0.  Dell recommends not jumping too many BIOS versions at once, but do about every other until caught up.  The part I don't like about that though is 2.10.2 gave speedstep (former Rockstar on this forum) trouble.  I can't remember if he was able to do BIOS recovery, but I think he got it going again.

I just found a Dell article.  Skip 2.10.2 if it lets you.  Precision Towers 3420 & 3620: System hanging at the Dell Splash Screen or failing to POST 

All bios up dated, 2.10.2 seems to be no longer available.

Cpu changed for i7-7700k

One of those tense moments when the monitor doesn't light up, then the fans stop, and start again, then the little green led on the monitor puts a smile on my face. All done.

One question before I go, the cpu is 4.2ghz, it take it that it can achieve it's turbo speed of 4.5ghz?

Thank you for your help.

Yes, the turbo boost will kick in when the condition required.  You can test it by running a task like Windows Security full scan to trigger full CPU load.  At the same time, opening Task Manager and monitoring CPU in Performance tab.

Glad that you have a successful upgrade.

There's 3 heatsinks available for the 3620.  A little pancake model for 65w CPU's.  Then a bigger pancake for 80w PSU's   Then a nice big one with copper with the fan in the middle of it for 91w CPU's.. - Dell Precision Workstation Tower 3620 Cooling Heatsink Fan 0VWMTJ VWMTJ  i7-7700k is 91w.

I have a water cooler that I can use, but getting the radiator higher than the cpu is a problem in most tower units. Some thing else to do battle with ha' ha'.

Thank you all.

It makes me wonder if the radiator, with its fans of course, can somehow be attached to the case fan.  Or move the case fan if possible.

Oh dear, no, it isn't going to fit.

My radiator is full of air, so that needs to be fixed before use anyway.

On Youtube some guys did a comparison between air and water cooled, and air cooled came out on top. A very good point was what if the water pump stops working? 

https://www.youtube.com/watch?v=hr0qLLv3dKc 

  https://www.youtube.com/watch?v=23vjWtUpItk 

Well that makes life a little easier lol. 

Just a reminder - Be sure to go with a heatsink that can handle 91w CPU, like the one I linked above.