Question New GTX 1660 doesn't work on my build and I can't figure out why.

Sep 29, 2020
I bought a new GIGABYTE GTX 1660S from PB Tech after my GTX 1060 6GB died. Every time I install it, the PC refuses to POST. I can swap back to my spare R7 250 and the pc works fine.
My motherboard is a GA-78LMT-USB3 (rev 6.0) and when I went to PB Tech I was told that it's simply too old to work with a new GPU, despite it appearing to match the specifications. I was told this is because this specific motherboard received no BIOS updates.
I contacted Gigabyte and they told me that it's either the card is dead, the PCI E slot has an issue or my psu wattage is exceeded during startup which is why it won't POST.
PC part picker says my power use should be at 329W (Although I didn't add the wattage from my stock cpu cooler) and I have a 500W PSU.

Dear Rhykynok,
The GTX1660 should work on this motherboard as the specifications are met.

There are several concerns when it comes to related situations.
1. Motherboard PCIe slot issue
Since your GTX 1060 was working before, this is unlikely the case here.
2. GTX 1660 itself is not functioning
To confirm this, need to install this in another system to find out.
3. Insufficient power supply unit
The recommended PSU for the GTX 1060 is 400W, while the GTX 1660 is 450W.
The entered power supply you have is 500W. Though it seems to be enough, the instant power draw at boot up may exceed this 500W, causing the not POST issue, as well as power supply decline throughout usage.
In this specific case, we would worry about the power supply first, as it is less likely to see graphics card issue, and in this case, the power supplied lacks redundancy.
Since not many users will have extra equipment to test, we would recommend contacting original supplier of the motherboard or graphics card for help.
Should these pieces all work together? What can I do to make them compatible. I have tried resetting CMOS. I have also considered upgrading the rest of my computer but I don't have much money and would like to resolve this ASAP so I don't have to worry about forgetting details about this situation.

System Specs

GA-78LMT-USB3 (rev 6.0)


AMD FX6300

2 x 4GB DDR3 - 1866 CL9

2 x 320 GB Seagate Barracuda HDD

FSP Group Hexa+ 500W

Windows 10 Pro 64 bit
Hey there,

Some older motherboards using the old Award type bios and not a UEFI bios have issues with modern graphics cards. However, what's unusual in your case is, that normally includes the GTX1060!

Typically newer cards like the GTX1xxx and RX4xx/5xx have issue running in boards without a UEFI bios. The R7/R9 and GTX9xx or before typically work perfectly.

You can try update your bios to ensure you have the most recent one, and then try the GPU install again.

What is the make and model of your PSU? Not all PSU's are made equal even if they appear to be okay from the oust side. It could be the PSU is not giving the new card enough juice.