Windows 10 not recognizing new CPU: The fix

I helped my son replace the i5 CPU in his PC with an i7 to hopefully solve some occasional performance problems he was having. But when we booted the upgraded machine for the first time and pulled up task manager, Windows 10 still thought it was an i5. Here’s how to fix Windows 10 not recognizing a new CPU.

Windows 10 not recognizing new CPU
If Windows 10 is not recognizing your new CPU, deleting the CPU cores in Device Manager fixes it.

The problem is when you replace the CPU and the new CPU isn’t substantially different from the old one, Windows doesn’t recognize the change. I’m not sure if a jump from an i3 to an i7 is enough, but the jump from an i5 to an i7 was not.

I’m also not sure if the problem is just cosmetic. It did indicate the CPU was running at I-5 type speeds rather than the higher speeds of the new i7. But the problem is easy to fix.

Making Windows 10 recognize the new CPU

Click the windows logo in the lower left, and type device manager. Click on the device manager icon when it comes up. Then expand the processors section and right click on each CPU core and click remove. Windows will want to reboot. Say no. Proceed to remove all of the remaining cores. I know what feels weird pulling the CPU out of device manager, but don’t worry. You’re not pulling the rug entirely out from under the system. After removing the last core, reboot.

When windows comes back, it will recognize that it doesn’t know what kind of CPU it has, and it will query the system and repopulate device manager appropriately. When you pull up task manager or device manager, you’ll see the new CPU.

Let’s also talk about what to do if you don’t see as many cores as you expect. Because we ran into that too.

One more thing

There was one other thing we forgot when we were upgrading his CPU. After you’ve powered the system up, go into the BIOS and look for the hyper threading option. If your old CPU wasn’t hyperthreaded, this option will probably be disabled. If your new CPU has hyperthreading, which most i7s do, you want to enable that.

Hyperthreading can be controversial, mostly because in the days when it first appeared with the P4, it didn’t exactly deliver the performance boost Intel promised. At least not all the time. And of course, there’s some people who want to dissable anything that they don’t understand, and hyperthreading is hard to understand, so you know the rest.

Here’s the thing about hyperthreading. Chips that have it have existed for nearly 20 years now. That’s a lot of time to figure out how to use something and to code your software to take advantage of it. Hyper threading helps more often than not, and that’s been the case for a long time.

Unfortunately I can’t necessarily tell you where to find the option, because every PC BIOS is different these days, especially when you’re dealing with a name brand PC, but it’s usually under a section labeled something like performance or CPU options or something like that.

Keep in mind that the additional cores from hyperthreading do not perform the same as physical cores, but when you throw eight threads at a four-core CPU with hyperthreading, it will outperform a comparable four-core CPU without hyperthreading. Which is the whole idea.

Is upgrading a CPU worth it?

Here is a related question. Is upgrading a CPU worth it, or should you just get a new PC?

It’s a fair question, and maybe a little more complicated than it first sounds. I am not a huge fan of modern Intel sockets. I’m not sure I could come up with a better design, mind you, but it is possible to damage the socket when you are upgrading a CPU. If you have a really steady hand and good eyesight and very small tools, you can straighten the pins in the socket. I know it’s possible to do, and some people are good at it. I am not.

But the upside is for $75 you can really pep up an older PC with an i7 and make it hold its own with a newer PC that may cost you several times as much.

The trick is when you are changing the CPU, not to get in a hurry. I remember when I could change a CPU in 5 minutes. When I tried to do an upgrade in 5 minutes, I ended up ruining my CPU socket.$50 mistake, but unnecessary $50 mistake.

There are two notches on either side of Intel CPUs, and they line up with matching protrusions on the sockets. If you don’t line them up, that’s when you damage the socket. So don’t count on the CPU to line itself up. Place the CPU in the socket carefully, and make sure it fits tightly, with no slop, and that you can see the protrusions lining up with the notches. If all that looks good, there’s no danger. Go ahead and close up the socket and mount the CPU fan.

But if it’s not lined up, you’ll probably run into what I did. When you power the system up, the system shows some very brief signs of life, but quickly powers itself back down.

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2 thoughts on “Windows 10 not recognizing new CPU: The fix

  • October 28, 2021 at 10:15 am

    Technically, things like Hyperthreading can be a security hole.

    • October 28, 2021 at 4:20 pm

      If you are referring to Spectre and Meltdown, it takes more than disabling Hyperthreading to mitigate those. But for the majority of us, the most important thing we can do to protect ourselves from those types of hardware vulnerabilities (there’s one in DDR RAM too!) is to keep our web browsers up to date. You can go back to a 1.13 GHz P3 using SDRAM in the name of security if you’d like, ut you probably don’t want to live without some of the other things you give up if you do that. Some of those things being other measures that protect your security, come to think of it.

      I ran through this whole exercise after I wrote a blog post about Spectre and Meltdown for my then-employer. A VP called me up and asked if I would be willing to speak with the CISO of a major airline, who had called him and asked to speak with “whoever wrote that article.” We talked for a good 45 minutes about what to do, and that conversation led to a follow-up blog post. I’ve done a little bit of vulnerability analysis and risk analysis here and there.

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