In need of opinions before I blow cash on a temporary solution

[Brockllanders]

I apologize if this has not been posted in the correct group first of all.

System specs :

Case : Fractal design define R6
Mobo : Gigabyte GA-Z97X-gaming 5
HDD: 1 1tb
SSD: 1 tb patriot containing only windows 10 pro
NVME: 2 TB containing my games currently 800 gig remaining free.
CPU: i7 4790K at standard clocks
CPU cooler : nhd-14 paste re applied 8 months ago.
RAM : 16gig corsair vengeance 2333 ddr3 no OC 2x8 operating in slot 1 and 3 as duel channell
OLD GPU : EVGA 1070 sc
New GPU : amd xfx 6750 xt qick.
PSU : 750 watt cougar approx 8 years old.

Okay so the issue is that when i bought the patriot ssd pre-installed with windows from new, i started to notice that my system would run sluggish upon bootup and i would have to wait 2 minutes for it
to settle to then hit restart before i ever get a descent response from windows. And bearing in mind bloat ware is near zero, I have uTorrent that fires up on launch and steam this is all.

I first started to see this being a major issue 3 months ago when I started to play crusader kings 3 again after an absence, and the game would launch but run very sluggish. This was when using the EVGA 1070.
I didn't use any diognostic tools at all thinking ok the GPU is getting dated. So I bought the xfx 6750xt. But the slug upon start up continued. Until I restarted then it would run I would say 95% of what what i've previously
known it to run at.

Now recently i've bought on steam Aliens dark descent, Assassins Valhala, and the last of us part 2 that was a gift via the purchase of the GPU.

So I buy the GPU and get T>L>O>U free, fire it up and everything is fine for maybe 2 hours, bearing in mind i've never used AMD GPU before, and after 3 hours of use my screen went black and rebooted. Throughout the 70 hours I placed this
game I got maybe 9 shut downs in total. No freeze just a black screen and perfect restart. Above I mentioned CPU at standard clocks but i had raised this to 4.6ghz with temperatures fine and stability also.

Then I bought aliens dark decent and the issue happened more frequent so I returned the CPU back to stock settings and I could play for 1 hour then restart ( never a crash ) or 2 hours then restart.

Then I bought assassin's creed valhalla on sale on steam. 3 year old game I thought surely I won't get the same issue but over 28 hours of gameplay the system has done a reboot twice now.

My thoughts are on cold boot up the PSU is not ramping up correctly being old. Credit to cougar has not blown. And 2ndly the reboots are a reaction to modern graphics cards pulling twice as much of their rated power for short periods, and
this is what my psu cannot deal with.

The plan was to replace old with new, and 7800 x3d, was the goal and reach further than just air cooled by my noctua NHD-14 go water cooled with 2 360 rads, that i could later ajoin with the GPU once I bought one later down the line, that had
suppliers offering water blocks for.

But in the short term and this couldn't have happened at a worse time, because ATX 3.0 is now a thing and the GPU standard nVidia are pushing which AMD have not yet adopted means there is a limited number of vendors giving options. Yet
anyone needing to replace a PSU should think of these 2 things, else replace again when ATX and the 12pin gpu connector become a must.

At haste i found a PSU that fits my budget that I can buy now : Thermaltakes tough power GF3 @ 1200 watts for only 159 GBP.

But do you guys think this is the issue and if so is this the option to take?
Many thanks

https://www.tomshardware.com/reviews/thermaltake-toughpower-gf3-1200w-atx-v30-power-supply-review
https://www.tomshardware.com/reviews/thermaltake-toughpower-gf3-1200w-atx-v30-power-supply-review

 

[Brockllanders]

quite a bit of info here, in terms of what i think may be the issue is as you have pointed out is the psu, your unit has done well lasting 8 years but as with the next gen gpu's requiring so much more power, i would say your current unit if falling behind under load, your current system even with the new gpu should be pulling no more than 500w from the wall under full load.

If your looking at a complete rebuild including the 7800x3d and a custom loop, instead of the monster 1200w your thinking of buying, maybe opt for a good quality 850w to max 1000w, the latest gen tech excluding some gpu's are very power efficient so you simply dont need a crazy high psu, if you intent to keep the 6700xt but pair with a 7800x3d then look at psu's in the 850w region gold rated minimum.

If you want to go the high end gpu route like a 4080+ or 7900xt/xtx then you should be looking in the 1000w region again like the 850w option look for a decent gold rated or higher unit

For a short term fix with the hardware you have a decent 850w will be more than enough brands such as corsair, asus, seasonic and be-quiet would be some of my brands to shop with, even if you then updated to the 7800x3d the newer 850w unit will power it and the 6700xt no problem at all, and a custom loop if you did that.

Thank you for your timely response on this matter. Yeah just like you I totally think its a PSU issue. The fact that the rail doesn't fully ramp up on 1st boot is an odd one. But once rebooted and especially how we are in summer now. I think the psu
the hotter it is getting is getting less efficient and thus shutting down. Or like the newer age of GPU's are often doing is spiking at 2x its stated power draw. which AMD software is showing me 218 watts at full load so that could be a whopping 436
when these spikes occur.

Hence why I think the way people think about a power supply now needs to change. I had calculated with wattage similar to what you mentioned and thought I had the headroom. But for my instance I think now 1000watt bare minimum and 1200 watt
with my future plans in mind.

But like I say thanks for the reply. PSU wattage was never so complicated as it has been for the past 2 GPU gens.

And the PSU I chose was purely down to what was on sale from the top tier list of ATX 3.0 compatible on cultist networks PSU tier list.