When I was building the Fujitsu TX140 S2, I wanted to purchase a SATA controller to expand the capacity from 6 SATA devices to 12. The ASMedia ASM1166 seemed most interesting as it is a modern design offering six SATA3 6Gbps ports without use of a port multiplier.

Despite what the silk screen on the PCB states, it is not “PCIe 3.0 x4” except in PCIe slot dimensions (since there is no standard for a physical PCIe x2 connector). The ASM1166 has a PCIe 3.0 x2 interface:

So the ASM1166 cannot provide full bandwidth to six SATA3 devices, but it is not as bandwidth limited as other SATA controllers which have only a PCIe x1 host connection. Be aware that the bandwidth will be halved if you install it in a PCIe 2.0 slot, due to the less efficient encoding of PCIe 2.0 (8b/10b) versus PCIe 3.0 (128b/130b).

The board designer did properly route the PCIe x2 connection to the host, as confirmed by lspci:

02:00.0 SATA controller: ASMedia Technology Inc. Device 1166 (rev 02) (prog-if 01 [AHCI 1.0])
        Subsystem: ZyDAS Technology Corp. Device 2116
        Physical Slot: 3
        Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr+ Stepping- SERR+ FastB2B- DisINTx+
        Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
        Latency: 0, Cache Line Size: 64 bytes
        Interrupt: pin A routed to IRQ 26
        Region 0: Memory at f7a82000 (32-bit, non-prefetchable) [size=8K]
        Region 5: Memory at f7a80000 (32-bit, non-prefetchable) [size=8K]
        Expansion ROM at f7a00000 [disabled] [size=512K]
        Capabilities: [40] Power Management version 3
                Flags: PMEClk- DSI+ D1- D2- AuxCurrent=0mA PME(D0+,D1-,D2-,D3hot+,D3cold+)
                Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-
        Capabilities: [50] MSI: Enable+ Count=1/1 Maskable- 64bit+
                Address: 00000000fee00298  Data: 0000
        Capabilities: [80] Express (v2) Endpoint, MSI 00
                DevCap: MaxPayload 512 bytes, PhantFunc 0, Latency L0s <64ns, L1 <1us
                        ExtTag+ AttnBtn- AttnInd- PwrInd- RBE+ FLReset- SlotPowerLimit 75.000W
                DevCtl: CorrErr+ NonFatalErr+ FatalErr+ UnsupReq-
                        RlxdOrd- ExtTag+ PhantFunc- AuxPwr- NoSnoop+
                        MaxPayload 128 bytes, MaxReadReq 512 bytes
                DevSta: CorrErr- NonFatalErr- FatalErr- UnsupReq- AuxPwr- TransPend-
                LnkCap: Port #0, Speed 8GT/s, Width x2, ASPM L0s L1, Exit Latency L0s <4us, L1 <64us
                        ClockPM+ Surprise- LLActRep- BwNot- ASPMOptComp+
                LnkCtl: ASPM Disabled; RCB 64 bytes Disabled- CommClk+
                        ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-
                LnkSta: Speed 8GT/s (ok), Width x2 (ok)
                        TrErr- Train- SlotClk+ DLActive- BWMgmt- ABWMgmt-
                DevCap2: Completion Timeout: Not Supported, TimeoutDis-, NROPrPrP-, LTR-
                         10BitTagComp-, 10BitTagReq-, OBFF Not Supported, ExtFmt-, EETLPPrefix-
                         EmergencyPowerReduction Not Supported, EmergencyPowerReductionInit-
                         FRS-, TPHComp-, ExtTPHComp-
                         AtomicOpsCap: 32bit- 64bit- 128bitCAS-
                DevCtl2: Completion Timeout: 50us to 50ms, TimeoutDis-, LTR-, OBFF Disabled
                         AtomicOpsCtl: ReqEn-
                LnkCtl2: Target Link Speed: 8GT/s, EnterCompliance- SpeedDis-
                         Transmit Margin: Normal Operating Range, EnterModifiedCompliance- ComplianceSOS-
                         Compliance De-emphasis: -6dB
                LnkSta2: Current De-emphasis Level: -3.5dB, EqualizationComplete+, EqualizationPhase1+
                         EqualizationPhase2+, EqualizationPhase3+, LinkEqualizationRequest-
        Capabilities: [100 v1] Advanced Error Reporting
                UESta:  DLP- SDES- TLP- FCP- CmpltTO- CmpltAbrt- UnxCmplt- RxOF- MalfTLP- ECRC- UnsupReq- ACSViol-
                UEMsk:  DLP- SDES- TLP- FCP- CmpltTO- CmpltAbrt- UnxCmplt- RxOF- MalfTLP- ECRC- UnsupReq+ ACSViol-
                UESvrt: DLP+ SDES+ TLP- FCP+ CmpltTO- CmpltAbrt- UnxCmplt- RxOF+ MalfTLP+ ECRC- UnsupReq- ACSViol-
                CESta:  RxErr- BadTLP- BadDLLP- Rollover- Timeout- AdvNonFatalErr-
                CEMsk:  RxErr- BadTLP- BadDLLP- Rollover- Timeout- AdvNonFatalErr+
                AERCap: First Error Pointer: 00, ECRCGenCap- ECRCGenEn- ECRCChkCap- ECRCChkEn-
                        MultHdrRecCap- MultHdrRecEn- TLPPfxPres- HdrLogCap-
                HeaderLog: 00000000 00000000 00000000 00000000
        Capabilities: [130 v1] Secondary PCI Express
                LnkCtl3: LnkEquIntrruptEn-, PerformEqu-
                LaneErrStat: 0
        Kernel driver in use: ahci

Power consumption is very good, the card only draws 2.8W idle.

PCIe SATA controllers based on the ASM1166 are comparatively priced to other 5-6 port SATA controllers, but offer more bandwidth than cards using the JMicron JMB585 or Marvell 88SE9125. ASM1166 controllers can be found for around 20€ on AliExpress. There are seemingly some sellers shipping cards with PCIe x1 connectors, so I would advise you to check the reviews of other customers to see which variant the seller sends.

I was unable to find detailed information about the card such as power consumption and lspci output online, which I find very useful when making purchasing decisions, so I thought I should write a short summary. This is not a review or endorsement of any online marketplace or brand.