Here is a blast from the past. In case you were not aware of, INTEL never officially released the Core i5-7660X Skylake-X CPU to the consumer market. Though some samples actually landed in the hands of select few overclockers, but apart from this we never got any relevant info or details on this SKU.
Now, it appears that one Chinese user @Zed_Wang recently obtained a working sample of this 7’th gen Skylake-X Core i5-7660X CPU, and he has posted his findings along with CPU-Z screenshots on Twitter.
The Core i5-7660X is based on the “Skylake” microarchitecture, fabbed on the 14nm+ process node, and it uses the same old LGA2066 Socket. The Core i5-7660X inherits all attributes of Skylake-X, like support for a “quad-channel” memory (128GB), AVX-512 instructions, 28 PCIe lanes etc.
Had Intel previously released the Core i5-7660X, then it would have been the first Core i5 HEDT processor, and also the first Core i5 to support quad-channel memory. But unfortunately Intel had others plans at that time. This CPU never made to the Retail market.
This is a 6 Core 6 Thread SKU, having 8.25MB of L3 cache with 3.4GHz as the base clock, and 5Ghz boost clock. The boost clock is the highest in the entire Skylake-X family though.
Looking closely at the specs we can conclude that the Core i5-7660X CPU is essentially an i7-7800X SKU, with higher clock speeds but without “Hyper-Threading”/HT. The TDP is also rated the same at 140 Watts. This SKU seems to be a cut-down variant/silicon of the 7800X SKU, or maybe Intel used some of the defective batch of “chips” of the i7 7800X processor.
The Core i5-7660X provides us with 28 PCIe 3.0 lanes, and supports DDR4-2400 memory modules just like the Core i7-7800X SKU. Why INTEL never released this CPU to the public remains a mystery.
My guess is that INTEL wanted to reserve the HEDT platform for its core i7 and above SKUs.