What are Port Multipliers (PM)?

Port Multipliers allow the connection of multiple Serial ATA devices to systems through a single Serial ATA port. Port Multipliers can be used for connecting any Serial ATA device, including SATA hard drives, SSD (solid state drive), other types of flash memory with SATA interface or SATA optical drives. The Port Multiplier offers unprecedented scalability, breaking the traditional Serial ATA connection topology of a single SATA device per port.

All the key advantages of Serial ATA technology over comparable interface solutions are preserved in the Port Multiplier. Both Serial ATA 1.5Gbps and Serial ATA 3.0Gbps devices are compatible, and the PM retains the 3.0Gbps SATA channel for connection to the SATA controller installed inside the host machine. With a supported 3.0Gbps SATA device and SATA controller, the Port Multiplier is able to take advantage of NCQ (Native Command Queuing). Similar to it's lower speed competitors USB 2.0/1.1 and Firewire 400/800, devices connecting to the PM hot swapped without system reset.

What are the benefits of using a Port Multiplier?

1. Port Multipliers increase the number of SATA devices which can be connected onto a single controller.
   
   Prior to the Port Multiplier, SATA controllers with 4 Serial ATA ports are limited to 4 SATA devices, one per port. To increase the amount of drives on the system, additional SATA controllers must be installed. With a Port Multiplier supporting up to 5 hard drives attached onto each of the SATA ports, a controller previously limited to 4 SATA devices is now able to simultaneously connect up to 20 SATA devices. This is beneficial to users who own a motherboard with very few or no bus slots available for adding SATA controllers.
   
   

   Example of a system configuration without Port Multipliers	Example of a system configuration with Port Multipliers

2. Port Multipliers reduce the amount of cabling required to connect an array of SATA devices.
   
   The SATA Port Multiplier combines several SATA devices into a single high speed 3.0Gbps SATA connection. In particular, this is an improvement for eSATA external storage units by allowing the convenience of only needing to connect one eSATA cable instead of requiring one cable per each device, with no substantial decrease in data transfer speed.
3. Port Multipliers are available with built-in Hardware RAID controllers for combining drives.
   
   Hardware RAID Port Multipliers are a great option when considering the creation of a redundant data storage solution. RAID capability is attributed to the built-in RISC chips which assume the load of handling RAID parity calculations, resulting in superior performance over software RAID sets which direct the processing load to the system CPU. At the same time, implementation of Hardware Port Multipliers avoid the cost of expensive Hardware RAID SATA controllers. The Silicon Image 4726 chip is able to create RAID 0, 1, JBOD, SAFE FAST, and SAFE BIG. The Oxford OXUFS936QSE chip is able to create FAST2 (2 drive RAID0 Striping), FAST4 (4 drive RAID0 Striping), SAFE2 (RAID1 Mirroring), SAFE FAST (Mirrored Striped), BIG 2 (2 drive Concatenation), BIG 4(4 drive Concatenation), RAID 3+S, or RAID 5+S using built-in hardware RAID.
4. A potentially unlimited number of hard drives can be daisy chained to a single SATA port using Hardware Port Multipliers.
   
   With a Hardware RAID Port Multiplier, drives connected configured as a single RAID volume (for example, a blazing fast 5 drive Striped set) can be attached onto any SATA port whether or not it is port multiplier compatible. This allows for a potentially unlimited amount of storage capacity by daisy chaining up to 5 Hardware Port Multipliers each fully populated with 5 hard drives onto one Hardware Port Multiplier for a total capacity of 25 hard drives through a single SATA or eSATA port. To the operating system all the drives appear as a single volume, yet a redundant RAID set still retains the ability to rebuild the RAID under the situation of data loss.
   
   
   
   
   
5. Port Multipliers are not only limited to SATA or eSATA interface.
   
   Newer Port Multipliers or storage enclosures utilizing Port Multiplier ASIC may now include other common interfaces such as USB 2.0, Firewire 400, or Firewire 800. For systems which do not have an available SATA or eSATA port to attach a Port Multiplier, these alternative interfaces can be used instead for better compatibility. eSATAp to USB 3.0 Adapters (ADU3ESA) can be attached onto Port Multipliers based on the 3726 which have no built-in USB support, allowing the connected drives to be seen as separate devices or as a single RAID volume on any computer with a USB 2.0/1.1 port. With hard drives set up as a single RAID volume using a hardware RAID port multiplier, the RAID volume can be connected to the computer through USB 3.0 using the Addonics USB 3.0 to eSATAp Adapter.

Addonics Port Multiplier Comparison Chart 1 (see chart 2 below for additional models)
Model #	AE5EHPMEU3	AD5ESAPM-E	AD5HPMREU	AD5HPMSXA	AD5HPMRXA-E
Type of Port Multiplier	External Hardware Port Multiplier (EHPM)	External Port Multiplier (EPM)	Hardware Port Multiplier (HPM)	Hardware Port Multiplier (HPM)	Hardware Port Multiplier (HPM)
Maximum number of storage Devices supported	5 eSATA drives	5 eSATA drives	5 SATA drives	5 SATA drives	5 SATA drives
Connect to system via SATA port	Yes. Any eSATA port	Yes. Any eSATA port	Yes. Any eSATA port	Yes. Any SATA port	Yes. Any eSATA port
Connect to system via USB port	Yes, USB 3.0 and USB 2.0	requires optional Addonics USB 3.0 - eSATA adapter (AAU3ESA)	Yes, USB 3.0 and USB 2.0	requires optional Addonics USB 3.0 - eSATA adapter (AAU3ESA)	requires optional Addonics USB 3.0 - eSATA adapter (AAU3ESA)
Supported enclosures or system	Any system with eSATA or USB port	Any system with eSATA	Rack mounted system with SCSI-I cut out. Addonics Storage Tower, Mini Storage Tower or Storage Rack. SCSI enclosure with SCSI - I back panel	Standard computer case with 1 free standard height or low profile PCI slot	Rack mounted system with SCSI-I cut out. Addonics Storage Tower, Mini Storage Tower or Storage Rack. SCSI enclosure with SCSI - I back panel
RAID Configuration requirement	using a set of onboard dip switches or RAID utility software	using the RAID utility1 of the SATA controller	using a set of onboard dip switches or RAID utility software	using a set of onboard dip switches or RAID utility software	using a set of onboard dip switches or RAID utility software
Supported RAID functions	RAID 0, 1, 10, BigDrive, 5, 5+S, N-Way Mirror	Dependent on the controller	RAID 0, 1, 10, BigDrive, 5, 5+S, N-Way Mirror	RAID 0, 1, 10, BigDrive, 5, 5+S, N-Way Mirror	RAID 0, 1, 10, BigDrive, 5, 5+S, N-Way Mirror
Drives can be configured to appear as individual drive to the OS	Yes when connecting to PM compatible controller or USB port	Yes when connecting to PM compatible controller	Yes when connecting to PM compatible controller or USB port	Yes when connecting to PM compatible controller or USB port	Yes when connecting to PM compatible controller or USB port
Integrated RAID controller	Yes	No	Yes	Yes	Yes
Bootable	Yes	No	Yes	Yes	Yes
Supported Type of Storage Devices	eSATA hard drives, eSATA SSD, CF (with Addonics SATA-CF adapters), eSATA optical drive	eSATA hard drives, eSATA SSD, CF (with Addonics SATA-CF adapters), eSATA optical drive	SATA hard drives, SATA SSD, CF (with Addonics SATA-CF adapters), SATA optical drive	SATA hard drives, SSD, optical driveCF (with Addonics SATA-CF adapters), SATA optical drive	SATA hard drives, SATA SSD, optical drive, CF (with Addonics SATA-CF adapters), SATA optical drive
Host Link Speed	1.5 / 3Gbits/s	1.5 / 3Gbits/s	1.5 / 3Gbits/s	1.5 / 3Gbits/s	1.5 / 3Gbits/s
SATA optical drive support	Yes when connecting to PM compatible SATA controller	Yes (cannot be used in simultaneous burn application)	Yes when connecting to PM compatible SATA controller	Yes when connecting to PM compatible SATA controller	Yes when connecting to PM compatible SATA controller
RAID status diagnostic	PM monitoring software	PM monitoring software	PM monitoring software	PM monitoring software	PM monitoring software
Support email notification	Yes	No	Yes	Yes	Yes
Maximum storage volume capacity	2TB with a 32-bit OS, 256TB theoretical maximum with 64-bit OS	2TB with a 32-bit OS, 256TB theoretical maximum with 64-bit OS	2TB with a 32-bit OS, 256TB theoretical maximum with 64-bit OS	2TB with a 32-bit OS, 256TB theoretical maximum with 64-bit OS	2TB with a 32-bit OS, 256TB theoretical maximum with 64-bit OS
LED connectors	Host link, storage device, individual drive activity, power and system ready	Host link, storage device, individual drive activity, power and system ready	Host link, storage device, individual drive activity, power and system ready	Host link, storage device, individual drive activity, power and system ready	Host link, storage device, individual drive activity, power and system ready
Supported Operating Systems	OS independent	Windows 2000, XP, 2003, Vista, Mac OS X and above, Linux kernel 2.62 and above	OS independent	OS independent	OS independent
Storage device can be hot swapped from the Port Multiplier	Yes	Yes	Yes	Yes	Yes
Port Multiplier can be hot swap from host	depends on controller	depends on controller	depends on controller	depends on controller	depends on controller
Daisy chain multiple Port Multipliers	Yes	No	Yes	Yes	Yes
Dimensions (W x D x H)	135mm x 65mm x 25mm	135mm x 65mm x 25mm	85 mm x 55 mm x 23 mm	85mm x 55mm x 23mm	85 mm x 55 mm x 23 mm
power connection requirement	USB power or external power adapter	external power adapter	standard floppy power connector	standard floppy power connector	standard floppy power connector
Chipset	JMB393	Sil3726	JMB393	JMB393	JMB393

Addonics Port Multiplier Comparison Chart 2
Model #	AD5SARPM-E	AD5SAPM	AD4SR5HPMUS
Type of Port Multiplier	Port Multiplier	Port Multiplier	Hardware Port Multiplier (HPM)
Maximum number of Storage Devices supported	5 SATA drive	5 SATA drives	4 SATA drives
Connect to system via SATA port	Yes. PM-compatible eSATA port	Yes. PM-compatible SATA port	Yes, any eSATA port
Connect to system via USB port	requires optional Addonics USB 3.0 - eSATA adapter (AAU3ESA). No RAID support	requires optional Addonics USB 3.0 - eSATA adapter (AAU3ESA). No RAID support	USB 2.0
Supported enclosures or systems	Rack mounted system with SCSI-I cut out. Addonics Storage   Tower, Mini Storage   Tower or Storage Rack. SCSI enclosure with SCSI-I back panel .	Standard computer case with 1 free PCI slot	Standard computer case with 1 free standard height or low profile PCI slot
RAID Configuration requirement	using the RAID utility1 of the SATA controller	using the RAID utility1 of the SATA controller	using onboard rotary switch
Supported RAID functions	Dependent on the controller	Dependent on the controller	2 drive RAID0, 4 drive RAID0, RAID1, RAID 10, BIG 2。BIG 4, RAID 5, or RAID 5+S
Drives can be configured to appear as individual drive to the OS	Yes when connecting to PM compatible controller or USB 2.0 port	Yes when connecting to PM compatible controller or USB 2.0 port	No
Integrated RAID controller	No	No	Yes
Bootable	No	No	Yes
Supported Type of Storage Devices	ATA hard drives, SATA SSD, CF (with Addonics SATA-CF adapters)	SATA hard drives, SATA SSD, CF (with Addonics SATA-CF adapters)	SATA hard drives, SATA SSD, CF (with Addonics SATA-CF adapters)
Host Link Speed	1.5 / 3Gbits/s	1.5 / 3Gbits/s	1.5 / 3Gbits/s
SATA optical drive support	Yes (cannot be used in simultaneous burn application)	Yes (cannot be used in simultaneous burn application)	No
RAID status diagnostic	PM monitoring software	PM monitoring software	via a lighting sequence of LEDs (LEDs are not included, pin header for LED is provided onboard)
Support email notification	No	No	No
Maximum storage volume capacity	2TB with a 32-bit OS, 256TB theoretical maximum with 64-bit OS	2TB with a 32-bit OS, 256TB theoretical maximum with 64-bit OS	2TB with a 32-bit OS, 256TB theoretical maximum with 64-bit OS
LED connectors	Host link, storage device, individual drive activity, power and system ready	Host link, storage device, individual drive activity, power and system ready	Host link, RAID status, individual drive activity, power, system ready and RAID diagnostic
Supported Operating Systems	Windows 2000, XP, 2003, Vista, Mac OS X and above, Linux kernel 2.62 and above	Windows 2000, XP, 2003, Vista, Mac OS X and above, Linux kernel 2.62 and above	OS independent
Storage device can be hot swapped from the Port Multiplier	Yes	Yes	Yes
Port Multiplier can be hot swap from host	Depends on controller	Depends on controller	Depends on controller
Daisy chain multiple Port Multipliers	No	No	Yes
Dimensions (W x D x H)	85 mm x 55 mm x 23 mm	85 mm x 22 mm x 49 mm	85mm x 55mm x 23mm
power connection requirement	standard floppy power connector	standard floppy power connector	standard floppy power connector
Chipset	Sil3726	Sil3726	OXUFS936QSE

note:

¹ Setting of the Port Multiplier requires configuration software from the controller, with the exception of the Hardware Port Multiplier (which uses it's own configuration software). 
² Certain older Linux distributions must patch the kernel with libata-tj-stable before they will support the Port Multiplier. Click here for instructions on how to patch the kernel under several Linux distributions.