Upgrade from Intel Core i5 2500K to 3770K on Gigabyte Z78MA-D2H-B3

I wanted to upgrade my computer without having to change the CPU, the motherboard and the RAM (prices are currently high because of shortages). So I looked what CPU I could use with my 10-years-old motherboard in order to replace the 2500K.

And the answer was the 3770K that is similar to the 2500K but double the number of threads from to 4 to 8 (see Intel's comparison).

I found a 3770K at a decent price on eBay. But changing from the 2500K CPU to the 3770K was not an easy task. Here is how I did it.

Switch to 3770K

The 3770K was released after the motherboard, and use the Ivy Bridge architecture instead of the Sandy Bridge architecture of the 2500K. The BIOS required a new version F10 to allow the motherboard to recognize that new CPU.

Thanks Gigabyte for still providing drivers and BIOS for the 10-years-old Z68MA-D2H-B3 rev 1.0!

It was easy to upgrade the BIOS by putting the F10 file on a USB stick then using the tool provided with the BIOS (QFlash) to load the file and update the BIOS.

The 3770K was detected and worked perfectly.

Then I tried to overclock it but the BIOS didn't allow to choose values over 3.9 GHz. Things started to be more complicated.

Overclock the 3770K

Gigabyte provide the U1C (UEFI BIOS) but a warning written in red says that it's a "Beta BIOS" and that "When updating from legacy to UEFI, use only the utility attached to your BIOS file". This sounded a little bit scary.

But some people have been able to use that beta UEFI without issue and I saw that it would allow the overclocking.

So I followed this guide to install FreeDOS and update from BIOS to UEFI.

Once I booted on the USB stick, I had to type FLASHEFI.EXE Z8MAD2H3.U1C, press enter and wait.

It failed the first time then worked the second time!

I was finally able to boot on the UEFI "BIOS", push the 3.9 GHz limit and overclock the 3770K to 4.4 GHz.


I had crashes at 4.5 GHz but it worked perfectly since I lowered the overclocking to 4.4 GHz.

The improvements are noticeable in the Multi-Core Score of Geekbench:

  • Intel Core i5-2500K @ 4.50 GHz = 3200
  • Intel Core i7-3770K @ 4.40 GHz = 3900

This matched with the expected results.

The Single-Core Score (about 1000) is slightly better because of improvements on the CPU architecture, but the lower frequency reduces this.