The Coffee Lake Refresh Silicon

At the heart of the Core i9-9900K is the new 8-core "Coffee Lake Refresh" silicon built on the same 14 nm++ process as the 8th generation Core processors. The die is laid out in the same essential design as "Skylake," with two rows of CPU cores sandwiching the ringbus, each core with a dedicated L2 cache and 2 MB slice of the L3 cache. Each core can address the entire 16 MB of L3 cache on the die. For the Core i9-9900K, all L3 cache slices are fully unlocked. For the i7-9700K, each core is configured with a 1.5 MB slice, which adds up to 12 MB. The 6-core i5-9600K is based on a die with only 6 cores physically available, and configured with 1.5 MB slices adding up to 9 MB. Intel is starting to reach the core-count barrier beyond which the ringbus has to be junked in favor of Mesh Interconnect tiles, or it will suffer the detrimental effects of ringbus latencies.


The ringbus is town-square and the primary intra-silicon communications fabric. It binds all eight cores with the uncore components (integrated northbridge, memory controller, PCIe root-complex, etc.) and the iGPU. Intel has improved the integrated memory controller to now support up to 128 GB of dual-channel DDR4 memory. For most users, this is meaningless, but if you plan on building a future-proof machine that will last the next seven years or so, you never know when you'll need more than 64 GB of RAM.


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.


A long-overdue innovation Intel introduced with the 9th generation is STIM, or soldered thermal interface material, Intel-speak for a soldered IHS (integrated heatspreader). Intel has been using thermal paste as the TIM between the CPU die and IHS for the past several generations, and in response to AMD implementing the soldered IHS across its entire lineup, Intel implemented it on at least the 8-core i9-9900K and i7-9700K. Some of the cheaper parts could continue to use thermal paste.

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.