Architecture

Unlike AMD, Intel doesn't manufacture just one kind of die with a large core count to then carve out lower core-count SKUs by disabling cores for the simple reason that its lower core-count SKUs sell in overwhelmingly higher volumes, and it would be a waste to for all 9th generation Core SKUs to be based on the 177 mm² 8-core die. The Core i5-9600K is built on a 6-core "Coffee Lake Refresh" die. The only things we deem to set this die apart from the "Coffee Lake" 6-core die of last year are hardware fixes to certain CPU security vulnerabilities and a refreshed integrated memory controller that now supports up to 128 GB of dual-channel DDR4 memory.


The "Coffee Lake Refresh" silicon driving the Core i5-9600K physically features six CPU cores with 256 KB of dedicated L2 cache per core and 12 MB of shared L3 cache. On the Core i5 "Coffee Lake" series, the L3 cache is reduced to 9 MB, which still keeps up with the 1.5 MB/core configuration of previous-generation Core i5 chips. Intel could maximize this silicon with its full 12 MB cache on certain mobile SKUs. The integrated Gen 9.5 graphics core is physically carried over from the "Kaby Lake" die. Internal communication is handled by a "ring bus" and not the mesh-interconnect Intel deployed on its new Core X "Skylake-X" processors.


Much of the processor's uncore components are clumped into the System Agent, which contains the memory controller, PCI-Express gen 3.0 root-complex, DMI interface, and memory PHY. On the other end of the ringbus is the Gen 9.5 integrated graphics, which has practically been carried over for the past three generations, featuring 24 execution units in the GT2 trim. At best, Intel may give it some software improvements that leverage the additional CPU power on tap. The iGPU is still branded under Intel's Graphics UHD family. Don't expect to play PUBG at 4K on this; the "UHD" moniker only indicates that the IGP can handle 4K Ultra HD displays, features modern connectivity options, such as DP 1.4 and HDMI 2.0, and can playback 4K video in new formats with 10-bpc color and HDR10/Dolby Vision standards.


Between "Skylake" and "Coffee Lake," Intel turned its R&D efforts toward refining the 14 nm process. It met with success on "Kaby Lake," and owing to its significantly higher clock speeds, "Kaby Lake" was able to provide higher performance than "Skylake." With "Coffee Lake," the nominal clock speeds look low, but Turbo Boost frequencies are higher than "Kaby Lake," and refinements in the process allow the chip to sustain elevated boost-clock states better. Between "Coffee Lake" (8th gen) and "Coffee Lake Refresh" (9th gen), the CPU core design has not changed. Intel did implement certain silicon-level fixes against security vulnerabilities.

The Intel Z390 Express Chipset

As we mentioned earlier, the only reason Intel appears to have launched the Z390 Express chipset while its existing Z370 chipset supports this processor through BIOS updates is because there could be motherboards with assured out-of-the-box support for 9th generation Core processors. Intel has also reportedly raised the CPU VRM requirements for the Z390, so motherboards based on it can maximize the overclocking headroom of the i9-9900K and i7-9700K. You can still overclock these chips with Z370. In terms of connectivity, the only thing that sets the Z390 apart from the Z370 is integrated 10 Gbps USB 3.1 and an external WLAN controller for 802.11ac.