MCIO, SlimSAS & Mini-SAS Cables: A Selection Guide

Server & storage interconnects

Compare six cable families for motherboard, controller, backplane and drive connections. Check the wiring, power and fit before ordering.

By Renhotec · October 8, 2026

RENHOTEC / SELECTION GUIDE

Server & storage.
Choose the right
cable.

MCIO · SlimSAS · Mini-SAS
Mini-SAS HD · OCuLink · U.2

MCIO x8 cable with straight and right-angle connectors, illustration

MCIO x8 cable with straight and right-angle ends. Illustration.

In this guide

01 / Start with the connection

What are you connecting?

A cable search often begins with a connector name: MCIO, SlimSAS or Mini-SAS HD. Before comparing part numbers, write down the two devices the cable must join. A motherboard-to-backplane connection needs a different review from a controller-to-drive connection, even when the plugs look familiar.

The equipment manual identifies the port’s signals; a photograph shows the housing, latch and cable exit. Together they help distinguish a mechanical match from a usable system connection.

START HEREHostMotherboard or controller

Interface · wiring · routeCable assembly

CONNECT TODestinationBackplane or drive

Identify the host and destination before choosing a cable.

The quick selection check

Identify both mating connectors, including their size and orientation.
Confirm the protocol, lane arrangement and required wiring at those ports.
Choose the connection layout: direct, cross-interface or breakout.
Check cable routing, power and the drawing for the exact assembly.

Choose the family from the installed ports first. Use the family overview below to identify the interface, then compare the configurations for your connection. Renhotec’s High-Speed I/O Cable Assemblies range provides the corresponding product configurations.

02 / Recognize the interfaces

Six cable families, with different jobs

The names below appear at different levels of a cable description. MCIO and SlimSAS identify connector families; U.2 commonly describes the drive-side interface. A cable can therefore belong in more than one search: an MCIO-to-U.2 assembly has an MCIO end and a U.2 end. Read the complete endpoint description before comparing two listings.

Interface reference for this guide
Family	Names to recognize	First selection question
MCIO	x4 / x8 configurations	Which port, lane arrangement and exit direction?
SlimSAS	SFF-8654, 4i / 8i	What protocol and wiring does this port require?
Mini-SAS	SFF-8087 / SFF-8088	Internal or external, and direct or breakout?
Mini-SAS HD	SFF-8643 / SFF-8644	Which connector and electrical implementation?
OCuLink	4i; SFF-8611 / SFF-8612 references	Which cable and mating-port specification?
U.2	SFF-8639 drive-side connection	What host connection and power feed are needed?

Renhotec MCIO x8 assembly with straight and right-angle ends — MCIO x8 · RHT-726-0001
Straight and right-angle ends

MCIO: compact connections with x4 and x8 options

MCIO is a compact connector family used in server and storage interconnects. Molex’s MCIO overview shows multiple circuit counts, plug designs and cable exits for space-constrained equipment.

Renhotec’s listed x4 and x8 assemblies include direct cables, x8-to-two-x4 breakouts and connections to other interfaces. A direct cable carries the connection to one endpoint; a breakout routes it to separate connectors. The platform’s lane arrangement determines whether those branches can serve the intended devices.

View MCIO configurations →
Read the MCIO cable guide →

Renhotec SlimSAS SFF-8654 4i cable showing both ends — SlimSAS 4i · RHT-726-1002
SFF-8654 at both ends

SlimSAS: SFF-8654 connections for storage systems

SlimSAS uses the SFF-8654 connector form factor; 4i and 8i are common labels in cable listings. Applications include SAS and PCIe connections, as shown in Amphenol’s internal interconnect overview. The equipment port determines the electrical use.

Renhotec’s range includes SlimSAS-to-SlimSAS cables, SATA breakouts and assemblies with Mini-SAS HD or U.2 at the other end. This makes the full endpoint description useful: “SlimSAS 8i to two Mini-SAS HD” describes a different physical route from “SlimSAS 4i to four SATA.”

View SlimSAS configurations →
Read the SlimSAS cable guide →

Renhotec internal Mini-SAS SFF-8087 straight-to-straight cable — Mini-SAS · RHT-726-2004
Internal SFF-8087 configuration

Mini-SAS: internal, external and SATA breakout cables

In this range, SFF-8087 identifies internal Mini-SAS configurations and SFF-8088 identifies external ones. Both may appear under “Mini-SAS cable,” so the SFF reference is the quickest way to separate the two when reading a listing.

A forward breakout connects an SFF-8087 controller port to individual SATA drives; a reverse breakout connects individual SATA host ports to a compatible SFF-8087 backplane. Direction describes endpoint roles and wiring, not one-way data flow.

View Mini-SAS configurations →

Renhotec external Mini-SAS HD SFF-8644 cable — Mini-SAS HD · RHT-726-3021
External SFF-8644 example

Mini-SAS HD: SFF-8643 inside, SFF-8644 outside

Mini-SAS HD uses SFF-8643 for the internal configurations discussed here and SFF-8644 for external configurations. These interfaces differ from Mini-SAS SFF-8087 and SFF-8088. For example, an internal cable joining an SFF-8643 controller to an SFF-8087 backplane needs a different connector at each end.

Check the electrical role as well as the connector: some SFF-8643 ports carry PCIe for an NVMe drive. Match the equipment’s specified port assignment before selecting an assembly.

View Mini-SAS HD configurations →

Renhotec OCuLink 4i cable with straight connectors at both ends — OCuLink 4i · RHT-726-4004
Straight-to-straight assembly

OCuLink: PCIe cabling between system components

OCuLink appears in PCIe cabling, including storage systems. Documentation may refer to SFF-8611 and SFF-8612 for the cable and mating connector. Renhotec’s listed 4i configurations include same-interface assemblies and connections to other storage interfaces.

View OCuLink configurations →

Renhotec SlimSAS to U.2 SFF-8639 assembly with a separate 15-pin power connection — U.2 connection · RHT-726-5001
SlimSAS host-side end and 15-pin power

U.2: the drive-side connection and its power feed

U.2 is commonly associated with the drive-side connection of a 2.5-inch NVMe SSD. SNIA’s SSD form-factor guide relates U.2 to the PCI Express SFF-8639 module specification. The host end may use MCIO, SlimSAS or another interface, so “U.2 cable” is only part of the description.

For a direct-drive assembly, include the separate power feed as well as the host signal route. A U.2 cable listing does not establish U.3 system compatibility: the drive, host and backplane must support the proposed arrangement.

View U.2 configurations →

MCIO-to-U.2 cable connected to a drive with a separate power tail, application illustration — **Direct-to-drive connection**Plan the signal-cable route and the separate power connection together.Application illustration

03 / Compare the interfaces

MCIO vs SlimSAS, and other common comparisons

MCIO and SlimSAS are different connector families with overlapping server and storage uses. Their plugs are not interchangeable. In an existing system, choose the assembly that matches both installed ports. A cable can have MCIO at one end and SlimSAS at the other when the equipment supports that connection.

MCIO vs SlimSAS: what actually changes?

Interface characteristics and examples from the Renhotec range
Selection point	MCIO	SlimSAS
Physical interface	Mini Cool Edge connector family; match the specified MCIO receptacle	SFF-8654 connector family; match the specified SlimSAS receptacle
Labels in this range	x4 and x8; straight, angled and breakout arrangements	4i and 8i; same-interface cables and breakouts
Where you encounter it	Compact server and storage links; PCIe interconnect applications	Storage-controller and backplane links; SAS or PCIe applications depending on the port
Representative routes	MCIO to MCIO, MCIO to SlimSAS, or MCIO to U.2	SlimSAS to SlimSAS, SATA, Mini-SAS HD or U.2
Mechanical choice	Plug exit direction, latch access and clearance around the installed port	Connector size, cable exit and the space needed for the selected branch arrangement
Performance comparison	Use the rating of the exact assembly at the required length and the equipment’s supported link mode. Neither family name establishes a universal speed ranking.

Molex specifies 0.60 mm pitch for its MCIO family, and Amphenol specifies the same pitch for its SlimSAS U10 connectors. Pitch alone therefore cannot identify a mating interface. Product-specific generation or data-rate claims in those manufacturers’ literature also do not rate a Renhotec assembly.

Which cable should you start with?

Replacing a cable: Start with the original assembly reference and the connector at each end. A different family would require a change at the mating connection.
Joining unlike ports: For an MCIO host port and a SlimSAS backplane port, look for an MCIO-to-SlimSAS assembly with the supported wiring. A passive cable does not convert PCIe into SAS.
Designing a new board: Compare the actual receptacle and plug drawings, supported channel performance and routing space before choosing a family. The cable and board connector form one connection design.

Mini-SAS, Mini-SAS HD, OCuLink and U.2

Common comparisons translated into a cable choice
Comparison	Direct answer	Selection consequence
Mini-SAS vs Mini-SAS HD	Different physical interfaces: internal SFF-8087 vs SFF-8643; external SFF-8088 vs SFF-8644	An SFF-8643 controller and an SFF-8087 backplane need a cross-interface cable, not a same-end replacement.
SFF-8643 vs SFF-8654	Internal Mini-SAS HD vs SlimSAS. These references identify connectors, not a single protocol.	An 8i SlimSAS-to-two-Mini-SAS-HD assembly routes one main connector to two ports. Its wiring must match the backplane application.
SlimSAS vs OCuLink	Separate connector families that can both appear in PCIe storage paths	Select by the host and destination ports. “PCIe cable” alone leaves the mechanical interfaces unspecified.
OCuLink vs U.2	They can be the two ends of one assembly: OCuLink at the system side and SFF-8639 at the drive	For a direct U.2 drive connection, include the power provision as well as the signal connection.

Connector, protocol and lane width answer different questions

01Connector

What physically mates?

Exact interface & orientation

02Protocol

What does the port carry?

Equipment specification

03Lane width

How is the link arranged?

x4 / x8 & branch mapping

The connector defines the mating interface; the port assignment defines the signals. For PCIe, x4 means four lanes and x8 means eight. A passive x8-to-two-x4 cable divides the assigned lanes between branches, so the host must provide two usable x4 links for two independent endpoints. It does not give each branch an x8 link or configure the host.

Identical endpoint names can also hide different wiring. Broadcom lists 05-60002-00 for a specified NVMe backplane arrangement and 05-60003-00 for SAS, both with SFF-8654 and two SFF-8643 ends. See page 3 of its controller cable guide. Those references demonstrate the distinction; they do not establish equivalence to a Renhotec SKU.

04 / Plan the connection

Direct, cross-interface and breakout layouts

Sketch the intended connection before selecting a cable. Label the host port, destination and each branch. This makes it easier to spot a missing power connection or an incorrect assumption about which device controls the link.

Direct example: MCIO x8 to MCIO x8 — Representative configurations illustrate the physical arrangement. Confirm wiring and system support separately.

Cross-interface example: MCIO x4 to SlimSAS 4i — Representative configurations illustrate the physical arrangement. Confirm wiring and system support separately.

Direct connections

A direct assembly joins two endpoints without separate branches. The two plugs can have different exits even within the same family: for example, straight at the controller and right angle at a backplane. Describe the orientation at each end independently.

Cross-interface connections

A cross-interface assembly joins different connector families, such as MCIO and SlimSAS. It is useful when the host and destination use unlike receptacles for a supported electrical connection. Record both endpoints in the cable name so a supplier can distinguish it from a same-interface assembly.

Illustration of an MCIO breakout beside an MCIO-to-U.2 cable with a separate power tail — MCIO breakout and MCIO-to-U.2 connection with a separate power tail. Illustration.

Breakout connections

A breakout divides the assembly into separately terminated branches. Give each branch a destination and identifier, then specify its length from a stated measurement point. Avoid describing every leg with one overall length if the receiving ports are spaced apart.

For a PCIe connection intended to serve multiple independent endpoints, check the platform’s supported lane arrangement. Some designs require bifurcation, which divides a link into separately usable groups of lanes. ASUS’s bifurcation support tables show that the available arrangements depend on the board, CPU and slot. A passive breakout does not create support that the platform lacks.

For SATA breakouts, use the forward/reverse connection roles described above. Label the host and drives or backplane in the sketch.

05 / Work through the details

A practical cable selection sequence

Capture the equipment references

Equipment record

Host modelPort labelDestination model

Record the motherboard or controller, port label, backplane and drive models, including hardware revisions. For a replacement, retain the complete cable label and suffixes. Add a connector close-up and a wider installation photograph.

For an equipment family with several backplane options, the server model alone may leave the storage connection ambiguous. Identify the installed backplane rather than choosing from a photograph of a similar chassis.

Define the electrical requirement

Electrical brief

ProtocolLane mapRequired generation

Record the protocol, lane arrangement and required generation or data rate. State whether the destination is a drive or backplane, and obtain the proposed assembly’s pin assignment and sideband information. Leave unresolved fields explicitly marked as unknown.

Ask the supplier what evidence is available for the required length and configuration. A continuity check can establish whether connections follow a wiring map; it does not by itself demonstrate high-speed operation in the intended system. Agree on the relevant electrical and system validation before a production order.

Measure the installed cable route

Installed route

Plug exitCable pathLatch clearance

Measure along the route the cable will actually follow. Include the space needed around fan shrouds, chassis edges and drive cages. State whether the requested length is measured between connector faces, cable exits or another defined point, and have that convention shown on the drawing.

Ask for the cable’s specified bend limits and provide enough room to respect them. Include latch-release access in the clearance review. A plug that fits during initial assembly may still be difficult to service after nearby modules are installed. Check both installation and removal in the intended chassis.

MCIO cable routed between a motherboard and storage backplane inside a server chassis, application illustration — **Server cable routing**Allow space for the cable bend and access to the release tabs.Application illustration

Review power and branch placement

Power & branches

Power sourceSplit locationBranch labels

For a power tail, specify its mating connector, required wiring and reach to the power source using the drive documentation. Show the signal and power routes on the same sketch.

Label each branch with its destination port and locate the split relative to the main connector. Each leg needs enough reach to avoid pulling on the others; branch labels should match the chassis port labels.

Approve the drawing and validate a sample

Drawing → sample

RevisionFit checkSystem validation

Review the proposed drawing against the request: endpoints, orientations, overall and branch lengths, pin assignment, power connection and labels. Keep the drawing revision with the selected SKU so procurement and engineering refer to the same configuration. Resolve differences before treating a quotation as technically approved.

Use a sample to check fit, device recognition and operation under the intended workload. Keep the equipment models, firmware, drawing revision and results together. Changes to length, routing or endpoints may require renewed validation; one sample result does not qualify an entire family.

06 / Specify the assembly

Turn a cable name into a usable specification

A request such as “SlimSAS 8i to two Mini-SAS HD ports” identifies the layout. Add the controller and backplane references, branch destinations and measured route to make it useful for a quotation. Separate fixed requirements, such as mating connectors, from preferences such as sleeve color.

Compare quotations against the same request

Use the same specification sheet for every offer. Record the proposed drawing revision, length convention, branch arrangement, test evidence and exceptions. An empty performance field remains unknown; it should not become an assumed rating when prices are compared.

If a quotation proposes a variation from the photo, identify the governing drawing. Carry that reference into the purchase order so engineering and procurement order the same assembly.

Keep a record for repeat orders

Retain the approved drawing, cable label, installation photographs and sample results. For the next order, identify changes in the equipment, cable length or route against that record. This gives the review a specific starting point instead of repeating the original selection process.

07 / Apply the checks

Five Renhotec cable configurations

These examples from the Renhotec configuration range show how an installation requirement leads to a candidate assembly. Final compatibility depends on the equipment and wiring specified for the order.

Configuration examples and the next question to resolve
SKU	Listed configuration	Check before ordering
RHT-726-0001	MCIO x8, straight to right angle; 30 AWG	Installed exit direction and clearance
RHT-726-0003	MCIO x8 to 2 × MCIO x4	Platform lane arrangement and branch mapping
RHT-726-0006	MCIO x4 to U.2 SFF-8639; 15-pin power	Host support, drive requirement and power routing
RHT-726-1001	SlimSAS SFF-8654 4i to 4 × SATA	Host/device roles and required breakout wiring
RHT-726-1003	SlimSAS SFF-8654 8i to 2 × Mini-SAS HD SFF-8643	Backplane implementation and signal mapping

MCIO x8 to MCIO x8 · right angle cable assembly — RHT-726-0001

CONFIGURATION 01 / EXIT DIRECTION

An angled MCIO connection in a confined space

MCIO x8MCIO x8 · right angle

RHT-726-0001 combines straight and right-angle MCIO x8 ends. It is a candidate when one port has room for a straight exit and the other sits close to an obstruction. The installation sketch should show which way the angled cable must leave the port. Its listed 30 AWG wire gauge does not specify a supported link speed.

View MCIO cable configurations →

MCIO x8 to 2 × MCIO x4 cable assembly — RHT-726-0003

CONFIGURATION 02 / BRANCH ARRANGEMENT

One MCIO connector feeding two branches

MCIO x82 × MCIO x4

For RHT-726-0003, label the two x4 destinations before asking for a quote. Include the host port’s documented lane arrangement and the route to each destination. If the branches must pass on opposite sides of a bracket, show that in the installation sketch. Confirm the available branch lengths and mapping for the proposed assembly.

View MCIO cable configurations →

MCIO x4 to U.2 + 15-pin power cable assembly — RHT-726-0006

CONFIGURATION 03 / POWER ROUTING

An MCIO-to-U.2 direct-drive arrangement

MCIO x4U.2 + 15-pin power

RHT-726-0006 combines an MCIO x4 end, a U.2 SFF-8639 end and a 15-pin power connection. For a direct-drive layout, the signal path runs between the host and drive while the power tail reaches a separate source. Specify those two reaches independently, especially when the drive cage and power connector sit on opposite sides of a bracket.

View MCIO cable configurations →

SlimSAS 4i to 4 × SATA cable assembly — RHT-726-1001

CONFIGURATION 04 / HOST / DEVICE ROLES

A SlimSAS-to-SATA breakout

SlimSAS 4i4 × SATA

RHT-726-1001 has a SlimSAS 4i end and four SATA ends. Identify the controller or motherboard port and the intended destination of every SATA branch. State the required host-to-device arrangement explicitly. If drive positions are numbered in the chassis, ask how branch identifiers should correspond to them so the installation can be checked without tracing every cable by hand.

View SlimSAS cable configurations →

SlimSAS 8i to 2 × Mini-SAS HD cable assembly — RHT-726-1003

CONFIGURATION 05 / BACKPLANE WIRING

A SlimSAS-to-Mini-SAS HD backplane connection

SlimSAS 8i2 × Mini-SAS HD

RHT-726-1003 provides a SlimSAS 8i end and two Mini-SAS HD SFF-8643 ends. It is a candidate for a route from one controller port toward two backplane inputs. Label both destination ports on the request; the Broadcom example above explains why this physical arrangement can require different wiring for different storage applications.

View SlimSAS cable configurations →

08 / Prepare your inquiry

Send the connection details with your SKU

To discuss a Renhotec assembly, include the following information. If a field is unknown, attach the relevant equipment page or a photograph so it can be resolved during the configuration review.

Renhotec SKU, if you have selected a starting configuration.
Host and destination models, revisions and port labels.
Connector requirements, protocol and intended lane arrangement.
Cable route, exit directions, lengths and branch destinations.
Power requirements, quantity and any drawing or validation requirements.

Browse the complete High-Speed I/O range for configuration options, or send your equipment details to Renhotec for review.

Discuss your cable configuration