Intel Z170 Chipset Summary
The Intel Z170 Chipset will be seen on most motherboard reviews that we publish here at HardOCP for the coming months. Before you dig through those however, what does the Z170 Chipset actually bring to desktop PC users? We give you a quick write up in hopes of covering what will be most important to you.
Z170 Express Chipset
Intel’s 6th generation Skylake Core i5 and i7 CPUs wouldn’t be complete without a new chipset to go along with those. Last week Intel introduced its Z170 Express chipset and LGA 1151 socket. In this case the chipset is a necessity given the changes to Skylake’s design architecture. Z170 isn’t by itself a massive improvement over the recent Z97 Express chipset. There are some important platform and design changes, but many of these exist at the motherboard level. I will get to that shortly.
The biggest change over last generation is DDR4 memory support. Z170 finally brings DDR4 to the mainstream platform and no longer relegates the technology to the expensive and high end X99 platform. The Z170 chipset was long rumored to support both DDR3 and DDR4. This is actually true but most of you won’t be able to utilize your old RAM along with a shiny new Z170 Express based motherboard and Skylake CPU. Support for DDR3 is limited to low voltage DDR3L modules with a maximum safe voltage of 1.35v. We have been told that some motherboard manufactures may at some point introduce specialty models which may circumvent this limitation but at this time we know of no specific models from any vendor. DDR3L isn’t really being embraced by the major motherboard vendors either so you will likely only see DDR3L support in small form factor or mobile applications for the most part.
Intel and memory makers are pushing DDR4 this generation and as production ramps up costs will come down even further. As it is the pricing of DDR4 memory has fallen quite a bit since X99 was introduced.
Improvements over Z97
Aside from DDR4 support, the most exciting improvement to Z170 Express is an increased number of PCIe lanes. Z170 now supports a total of 20 PCI-Express lanes at the PCH in conjunction with the CPU’s 16 PCIe 3.0 lanes for a platform total of 36. Last generation’s Z97 Express chipset coupled with Devil’s Canyon or Haswell CPUs only allowed for 24 lanes. All of these from the PCH were PCIe 2.0 compliant. In contrast all Z170’s PCI-Express lanes are Generation 3.0 compliant while retaining backwards compatibility with PCIe 2.0 and 1.0 specifications. Manufacturers will of course have a great deal of flexibility concerning how these are allocated. There will be a lot of additional integrated devices on Z170 motherboards so not all of those PCIe lanes will be free for use by the user via expansion cards. So keep this in mind.
Intel’s Management Engine interface or ME firmware has been raised to version 11. DMI 3.0 is being introduced with Z170 Express as well. The DMI or Direct Media Interface is used to connect the PCH to the CPU. Bandwidth for DMI 3.0 has increased significantly over 2.0. DMI is similar to PCI-Express in that it has multiple lanes and uses differential signaling to create a point to point link. In most applications 4x lanes are used for this although 2x lanes are used in some lower end applications. All PCH connected devices have to go across the DMI bus. The DMI 2.0 specification allowed for transfer rates of up to 20Gbit/s via an X4 link. DMI 3.0 increases bandwidth to 8GT/s or Gigatransfers per second. With DMI 2.0 there was a 20% overhead in the transfer protocols which has been reduced to around 1.5% or so in DMI 3.0 making it far more efficient.
Storage and Connectivity
Z170 still allows for up to 14x USB 2.0 ports but now allows for up to 10x USB 3.0 ports native to the chipset vs. 6x ports on Z97. Because USB 3.1 isn’t native to the chipset, a third party controller will have to be used in conjunction with the Z170 Express chipset. Intel offers the Alpine Ridge controller which handles USB 3.1 connectivity along with support for the new USB Type-C connector. Alternatively, some vendors may opt to use an ASMedia or competing controller for USB 3.1 connectivity. From what I’ve seen many if not all Z170 Express motherboards will probably feature USB 3.1 support through one means or another. So far I’ve seen solutions which use the Alpine Ridge controller and the ASMedia ASM1142.
The amount of SATA ports hasn’t been increased so the drive controller is largely unchanged from Z97. You still get 6x SATA 6Gb/s ports and a single SATA Express port which can be used as two SATA 6Gb/s ports. Because of the shift to PCIe 3.0, SATA Express which can now effectively support up to 16Gb/s of bandwidth provided you can actually find drives that support it.
M.2 support on last generation’s hardware was a mixed bag. Some vendors allocated only two PCIe Gen 2.0 lanes to the slot giving you a maximum of 10Gb/s of bandwidth. Other manufacturers would allocate as many as 4x PCIe Gen 3.0 lanes to the slot allowing for 32GB/s of bandwidth. Motherboards also lacked support to RAID multiple M.2 slots together in the rare instances that more than one M.2 device was present in the system. This is no longer the case with Z170. Unfortunately for users, you will find limited value in using multiple M.2 devices in RAID. DMI 3.0 has a maximum transfer rate of 8GT/s as stated earlier. Roughly translated, this should allow for up to 64GB/s of bandwidth for DMI 3.0 but you would be wrong. While the performance penalty of DMI 3.0 is extremely low, around 1.5% overhead, you are still limited by PCI-Express on the backend. In other words after overhead is accounted for you are going to see an actual limit of 40GB/s of bandwidth across the DMI bus. This effectively means that while you can RAID two M.2 devices together, but you won’t see the same type of scaling we're used to from SSDs. You should see a return of 1.4x or 1.5x at most over a single drive. Controller design and workload do factor in of course, but as you can see you hit a wall with diminishing returns very quickly with M.2 drives on Z170.
Thunderbolt 3.0 is Here and No One Cares
Thunderbolt when you get down to it is probably the best interconnect in the last decade or so. Its capabilities are undeniable and its original form is still as fast as USB 3.1. The physical layer left something to be desired. The connector sucked in that you could plug it in wrong with almost no effort and visually it was hard to tell which way it was supposed to go as it was nearly symmetrical. At least to those of us without perfect vision anyway. No one gave a crap about the connector because of the sheer lack of devices built to support it. Many motherboard manufacturers spoke of the possibilities with this connector but virtually nothing was realized except for a few odd storage devices.
Thunderbolt is back again but this time it’s reinvented itself. The Alpine Ridge controller I mentioned for USB 3.1 support earlier has Thunderbolt 3.0 support built into the ASIC as well. While not every motherboard manufacturer will use it, the controller will be a common sight on many motherboards. The USB 3.1 Type-C connector has provisions for "alternate modes" to be used over the physical layer. Indeed VESA signaling can be passed over USB Type-C which could lead to mini-DisplayPort being replaced in the long run. Apple is really the only company that actively embraced Thunderbolt as a standard, and now Thunderbolt compatible signals can now be passed through USB Type-C connectors as well thanks to Intel reworking Thunderbolt. Thunderbolt 3.0 can deliver up to 40Gbps in a single channel along with over 100 watts of power although support for power over Thunderbolt 3.0 beyond 15w is entirely optional.
Today USB 3.1 Type-C is a standard which is emerging but looks poised to replace the 1.0 style physical connectors we’ve loved to hate for over a decade. Thunderbolt never really did well on its own but it might gain some traction now that Thunderbolt signaling can be passed over USB 3.1 Type-C connections. Being able to pass video and audio through that connector only increases the likely hood of this happening over the long haul.
Thunderbolt 3.0 support from a motherboard standpoint is basically built into any with an Alpine Ridge controller and a USB 3.0 Type-C connector. There are some brands out there which will have Alpine Ridge on virtually all its motherboards so this is actually going to be pretty common. Unfortunately for Thunderbolt specifically is that its support is governed by firmware and ultimately certification from Intel, on a per motherboard basis. While I have admittedly only seen a handful of Z170 designs at this point, the bulk of them aren’t Thunderbolt certified. Many use ASMedia’s ASM1142 USB 3.1 controller which lacks the Thunderbolt 3.0 support in the ASIC.