As of last week, they’ve launched 2 new cards, the GTX 1660 and GTX 1660TI, both sub £/$300, and both really rather good. For a while now, if you had this sort of budget for a GPU, the RX 580 was a no brainer. Really, the GeForce GTX 1660 falls square between the Radeon RX 590 above and the Radeon RX 580 below; the latter card, in places, we're seeing for $199. Additional testing, though, has shown that... Jun 23, 2019 · The RTX 580 is equipped with a GPU codenamed Polaris 20 XTX while the GTX 1660 is codenamed TU166-300-A1. Core speed of the RTX 580 registers at 1257 MHz a bit lower than the GTX 1660 which is at 1530 MHz. The 580 can be boosted up to 1340 MHz while the 1660 can be boosted up to 1785 MHz.