Question PC refuses to start with new CPU

Apr 18, 2021
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I just installed a Ryzen 7 3700x into my PC and it refuses to start, the system fans don't even spin. I took it out and tried my old CPU and it works perfectly, so it's not an issue with my motherboard. BIOS is fully updated as well. No clue if it is a faulty cpu. Also tried reseating it and replugging all cables to no avail.
Motherboard: AB350m DS3h
PSU: EVGA 450w
 
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Apr 18, 2021
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Should also add that I am waiting on a mounting bracket for the cooler, so my PC is on it's side with the cooler on top that way. It's adequately cooled considering the old cpu ran fine like this.
 
Should also add that I am waiting on a mounting bracket for the cooler, so my PC is on it's side with the cooler on top that way. It's adequately cooled considering the old cpu ran fine like this.
Did you update the BIOS to a version that supports the new CPU? that would be rev F50. Gigabyte says to update first to F31, then F50.

You'll do this with the old CPU as the 3700X won't work otherwise. I would not attempt any of this, though, until the cooler is properly mounted. If the BIOS update fails for any reason it will leave your motherboard bricked.

After updating BIOS (or if you've updated to that level) be sure to reset CMOS. That motherboard is going to be pushed to the limits with a 3700X; B350 boards had weak VRM's across the board and that one is weak even for a B350. Good luck.
 
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Apr 18, 2021
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Did you update the BIOS to a version that supports the new CPU? that would be rev F50. Gigabyte says to update first to F31, then F50.

You'll do this with the old CPU as the 3700X won't work otherwise. I would not attempt any of this, though, until the cooler is properly mounted. If the BIOS update fails for any reason it will leave your motherboard bricked.

After updating BIOS (or if you've updated to that level) be sure to reset CMOS. That motherboard is going to be pushed to the limits with a 3700X; B350 boards had weak VRM's across the board and that one is weak even for a B350. Good luck.
I just ordered a B450 tomahawk, i was planning on getting a new mobo anyway. Also yes, I did update the bios. If the CPU doesn't work on the new mobo I will just send the cpu back.
 
I just ordered a B450 tomahawk...
Good idea!

I hope it's the B450 Tomahawk Max as they're made for Ryzen 3000 CPU's and will work out-of-the-box. But update BIOS anyway as later AGESA's have better performance and significantly better memory compatibility. I also notice your current board is mATX while Tomahawks are ATX boards... you better have an ATX case or it won't fit

I seriously doubt the CPU is faulty. Or at least wasn't when you got it since, while I tend to doubt it, you may have toasted it trying to run with the heatsink improperly mounted.
 
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Apr 18, 2021
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Good idea!

I hope it's the B450 Tomahawk Max as they're made for Ryzen 3000 CPU's and will work out-of-the-box. But update BIOS anyway as later AGESA's have better performance and significantly better memory compatibility. I also notice your current board is mATX while Tomahawks are ATX boards... you better have an ATX case or it won't fit

I seriously doubt the CPU is faulty. Or at least wasn't when you got it since, while I tend to doubt it, you may have toasted it trying to run with the heatsink improperly mounted.
Is there any way to tell if the CPU is fried beforehand? I don't think it is because I used the same cooling setup as the old CPU (ryzen 5 2600) when I popped it back in last night, and it worked fine. I have a hunch that the motherboard just doesn't want to handle the 3700x. Also is it safe to leave the 3700x in the plastic it came in while i'm waiting for the mobo? It's not going to move at all, it's just sitting in my desk.
 
Is there any way to tell if the CPU is fried beforehand? I don't think it is because I used the same cooling setup as the old CPU (ryzen 5 2600) when I popped it back in last night, and it worked fine. I have a hunch that the motherboard just doesn't want to handle the 3700x. Also is it safe to leave the 3700x in the plastic it came in while i'm waiting for the mobo? It's not going to move at all, it's just sitting in my desk.
I know of no way to test a CPU out of a system or without a special purpose test rig of some sort.

CPU's don't operate in full performance modes until everything is initialized and the OS starts to load up. I don't even think all 8 cores are enabled in BIOS as they're not needed. Although, CPU power saving features are also not enabled, that's why they can get pretty warm just in BIOS on only one core. But the CPU may never have gotten hot enough and even if it did protections might just shut it down before it got to the point of damaging it. So, you may be correct and the problem really is that your system simply can't handle a 3700X....either that or properly clamping on the heatsink will cool it correctly and allow it to work. But B350's never were intended to run 3rd gen and it's a bit dodgy trying to run one on them even when it works right.

Lastly; 3rd gen CPU's are a far cry different from any of the 1st or 2nd gen. They're designed to run very close to silicon limits by design. That makes them far more sensitive to cooling problems. Just because it works with your 2600 is no reason to assume it will with a 3700X.

Assuming this is what you mean, it's perfectly safe sitting in the clam shell package it came in. It's designed to protect the delicate pins as well as against electro-static discharges.
 
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Apr 18, 2021
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I know of no way to test a CPU out of a system or without a special purpose test rig of some sort.

CPU's don't operate in full performance modes until everything is initialized and the OS starts to load up. I don't even think all 8 cores are enabled in BIOS as they're not needed. Although, CPU power saving features are also not enabled, that's why they can get pretty warm just in BIOS on only one core. But the CPU may never have gotten hot enough and even if it did protections might just shut it down before it got to the point of damaging it. So, you may be correct and the problem really is that your system simply can't handle a 3700X....either that or properly clamping on the heatsink will cool it correctly and allow it to work. But B350's never were intended to run 2nd gen and it's a bit dodgy trying to run one on them even when it works right.

Assuming this is what you mean, it's perfectly safe sitting in the clam shell package it came in. It's designed to protect the delicate pins as well as against electro-static discharges.
Thanks, you've been a big help. There's nothing worse than thinking I <Mod Edit> up a 320 dollar chip when it's actually just my mobo crapping out.
 
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