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ASUS Z97 Pro (Intel Z97) Motherboard - Circuit and Overclocking Guide (Page 3)

By: Steven Bassiri from Aug 11, 2014 @ 9:12 CDT

Motherboard Circuit Analysis


The Z97 PCH only provides eight PCI-E 2.0 ports, and if you want SATA Express, then you can only get six of those eight ports. SATA Express was made possible with Z87, Intel employed an IO solution referred to as FlexIO, originally it was to allow manufacturers to decide whether to trade USB 3.0 and/or SATA 6Gb/s for PCI-E bandwidth.

Board designers took advantage of this overlay of SATA and PCI-E and are now able to use the two FlexIO PCI-E ports designated to switch between SATA and PCI-E to work with SATA Express and M.2.


You could say that the Z97 Pro's connectivity is a juggling act employing countless switches continuously working to provide bandwidth to devices in use. If all the PCI-E connected devices sans the M.2 and SATA Express were to work at full speed, they would require a total of 12 PCI-E 1x lanes, however there are only six PCI-E 1x lanes left after SATA Express and M.2. ASUS uses a few different methods including swapping bandwidth, sharing bandwidth, and both swapping and sharing in some cases.


The ASMedia ASM1480's in the image above are only involved in switching 8x of PCI-E 3.0 from the CPU to either the first or second PCI-E 16x slot for SLI and CrossFireX. However, there are two other chips in the image, an ASM1184e and ASM1440. The ASM1184e takes in one PCI-E lane and outputs four; this is a common method to increase PCI-E lanes for devices that might not saturate it.

In this case, it provides PCI-E to the extra ASMedia SATA controller, three PCI-E 1x slots (two are switched through the ASM1440 in the picture), and the Wi-Fi/BT module. While the ASM1440 in the picture above decides whether one of two PCI-E 1x slots get bandwidth, there are two others on the board which help juggle bandwidth between the 4x PCI-E slot, a 1x PCI-E slot, and a USB 3.0 controller.


First we have the ASM1061, for the PCI-E bandwidth to get to the ASM1061, it must first go all the way to the ASM1184e pictured earlier, then back to the ASM1061. This IC provides two SATA 6Gb/s ports, ASUS says the two ASMedia powered ports are to only be used for hard drives. The Intel NIC is one thing you don't really want to route through a switch, the i218 above is Intel's latest iteration featuring ultra-low power consumption.


The ASMedia 1042 is a common USB 3.0 controller, it provides two USB 3.0 ports at the top of the back panel. For the PCI-E bandwidth to get all the way up there, it has to first go to an ASM1440, which could potentially impact PCI-E signal integrity, so ASUS employed a re-driver. The ASMedia ASM1467 sits on the back of the motherboard and it strengthens the signal allowing it to carry information back and forth across half the length of the board to the ASM1042.


The audio part of this board is well done, the isolation is not only between digital and analog signals on the board, but also between the left and right audio channel. ASUS is using an ALC1150, which is under cover, however they decided to use a Texas Instruments RC4580I amplifier for the front headphone port.

ASUS has also decided to use a few Nichicon electrolytic capacitors for the audio which is a step in the right direction. The UEFI is on a 64Mbit/8MB ROM, a tiny little chip labeled BIOS is used for the USB flashback feature that ASUS has.


The ASM1442K is a level shifter, it allows HDMI signal to come from the digital output the integrated GPU in the CPU provides. The ASM1480 is a PCI-E 3.0 quick switch used to switch between M.2 and SATA Express.


A nuvoTon (formerly Winbond) NCT6791D provides SuperIO capabilities such as voltage monitoring and fan control. A proprietary chip which is labeled TPU provides EC functions such as auto-overclocking.

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