The Z170 Chipset; PCI-E Lanes Aplenty
The Z170 Chipset; PCI-E Lanes Aplenty
Much of the news about Skylake will be focused on the processors themselves but the Z170 chipset is arguably the more interesting aspect of this launch. It will usher in a whole new generation of motherboards, ones which are infinitely more capable of adapting to upcoming connectivity technologies. That's is particularly important since it looks like this chipset in one form or another may be with us for the better part of two years.
With so many devices moving over to the PCI-E bus, the outgoing Z97 chipset’s eight integrated Gen 2.0 lanes were proving to be a major hindrance for future expansion opportunities. Granted, some of the Flex I/O ports could be configured as for additional lanes but motherboard manufacturers were still dealing with a primary layout that dated back to the P67 Express days. With NVMe, M.2, USB 3.1 and even the ill-fated SATA Express interface all eating up significant amounts of bandwidth, those eight lanes proved to be woefully inadequate and some boards actually “stole” lanes from the graphics slots to feed higher end storage devices. The situation needed to change in a big way if Intel had any hope of providing a modicum of future-proofing for their newest processors.
Even though a number of design components haven’t been officially announced or detailed yet, a top-level look at the new Z170 PCH and its interface with Skylake processors still provides some interesting insights. First and foremost, the baseline graphics PCI-E capabilities of Skylake processors haven’t changed from previous generations; there’s still a total of 16 PCI-E 3.0 graphics lanes that can be configured in 1x16, 2x8 or 1x8 + 2x4 formats. There’s also support for three display outputs alongside HDMI 2.0 and DisplayPort 1.2 certifications.
Those CPU-bound display and PCI-E lanes seem to be some of the only elements carried over from previous designs. In the place of the old DDR3 controller the Skylake processors boast a new dual-use controller that can switch between standard high speed DDR4 or low voltage DDR3L for SFF and mobile applications. The Direct Media Interface which is charged with communication between the CPU and PCH has also been thoroughly upgraded to a third generation format and boasts drastically increased bandwidth of 8GT/s in order to better handle the chipset’s new capabilities.
Moving down to the Z170 itself, things start to get really interesting. In the place of those aforementioned outdated PCI-E 2.0 lanes there’s now a grand total of 20 PCI-E Gen 3.0 lanes. While Intel hasn’t exactly been forthcoming about how this copious number of lanes is doled out through their Flex I/O interface, some will likely pull duty for Ethernet, SATA and USB connectivity while the remainder can be dedicated towards additional PCI-E slots or PCI-E-based storage devices. This flexibility is why all of the SATA and USB figures are given an “up to” number as motherboard manufacturers are relatively free to spec their own layouts.
The availability of PCI-E 3.0 lanes for high bandwidth storage support is certainly a big step in the right direction but native USB 3.1 and Thunderbolt support are both still missing in action. Those interfaces can be added through third-party controllers and will access the chipset via the PCI-E 3.0 lanes so Intel’s partners can certainly add them if the situation dictates.
Aside from the PCI-E bonanza there are a few other changes to the chipset as well. For example, Intel’s RST service has been brought forward into the PCI-E storage sphere, allowing RAID arrays to be built with today’s fastest drives. Intel’s Smart Cloud Technology is being integrated here too.
To take an example from a higher end motherboard, ASUS’ Z170 Deluxe represents an excellent example of what this new platform is capable of since it utilizes a full array of controllers and the chipset’s native capabilities to deliver a full array of connectivity options in a great looking (albeit expensive) package. Naturally, the Z170-A doesn't have quite these capabilities.
There is quartet of both USB 3.0 and USB 2.0 outputs dedicated towards the board front panel connectors while two additional ports are housed on the board’s rear I/O area for the BIOS Flashback and Keybot features. Meanwhile, the Audio Codec is handled by a Realtek ALC1150, a single PCI-E lane feeds into an Intel 219 LAN network module and there’s a pair of native SATA 6Gbps ports.
High speed internal storage is handled in two different ways. There are two PCI-E lanes and a pair of SATA ports coupled together to provide bandwidth for a single SATA Express port (the two SATA connectors can be used separately as well) while four PCI-E lanes and those same two native SATA interconnects provide communication between the PCH and the onboard NVMe-enabled M.2 slot.
An additional four PCI-E lanes feed into an ASMedia 1480 switch, feeding a pair of additional SATA 6Gbps ports and the single additional PCI-E 3.0 x16 slot (which operates in x2 mode). If a user needs more bandwidth to this slot for higher end storage solutions it can be set to use all four lanes via a simple BIOS input, thereby disabling the attached SATA_5 and SATA_6 ports. Take this little foible into account when installing a x4 PCI-E SSD alongside SATA-based devices.
Things start to get really interesting when looking at how ASUS implemented the Deluxe’s tertiary functions. There’s a single ASMedia 1187e PCI-E switch that takes a single lane and multiplies it into seven individual x1 connections. These are then used to provide bandwidth to the four Gen2 x1 slots as well as an Intel i211 Ethernet controller and a single eSATA port. The final lane provided by this switch is converted to a USB 2.0 interconnect that feeds ASUS’ onboard Bluetooth / WiFi module.
The final part of this somewhat complicated puzzle is the way the Deluxe handles USB 3.1. There are three pairs of PCI-E lanes, each of which funnels its bandwidth towards a dedicated ASMedia 1142-1 PCI-E to USB 3.1 switch. Those three switches each provide sufficient power for this board’s five USB 3.1 Type-A connectors and a single Type-C connector.
While the Deluxe takes an “everything but the kitchen sink” approach to device support, ASUS’ other boards like the Z170-A go down a slightly more straightforward route. While we will still see plenty of support for the likes of USB 3.1, SATA Express, M.2 and PCI-E SSDs, the number of third party switches will be drastically reduced, simply providing less ports rather than eliminating any key functions.
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