CSPS Common Slot Server Power Supply Interface and Pinout

Thu, 16 Apr 2026 23:11:04 +0800

CSPS here refers to Common Slot Server Power Supply, also often called Common Slot Power Supply. These power supplies are common on HP / HPE ProLiant server platforms. Their typical characteristics are:

Modular hot-plug power supply form factor.
Mainly 12V output, suitable for centralized server backplane power distribution.
64 pin edge connector / gold finger interface to the backplane.
In addition to high-current 12V and GND, they also provide 12VSB standby power, enable signals, status signals, and a PMBus / SMBus / I2C management interface.

These power supplies are common on the used market, such as DPS-750RB and DPS-1200FB. They have high power density and are usually inexpensive, making them useful as lab 12V high-current supplies, charger front ends, 3D printer / CNC / radio equipment power supplies, or custom server PSU backplanes.

Note that Common Slot is more of a common slot form factor within a server vendor ecosystem. It is not the same kind of broadly published consumer standard as ATX. Different models are often very similar, but before building a breakout board or applying power directly, it is still best to compare the specific PSU model documentation and actual measurements.

Interface Structure

Common CSPS power supplies use a 64 pin edge connector for output. Based on Jayy’s open-source breakout board project, the connector can be a 2.54mm pitch 64 pin edge connector, for example:

Vertical: WingTat S-64M-2.54-5
Right angle: WingTat S-64L-2.54-5

The high-current section is not carried by a single pin. Instead, multiple 12V and GND pins are paralleled. This reduces current per contact, lowers heating caused by contact resistance, and makes current sharing on the backplane easier.

The signal section is concentrated in the middle pins and includes:

EN: main output enable control.
PRE: power supply present detection.
12VSB: standby 12V, usually always on when AC input is present, with limited current capability.
SCL / SDA: PMBus / SMBus / I2C communication.
PSOK: power supply OK signal.
IMON: current monitor signal.
PSIN: alarm / status related signal.
ADR: PMBus address related pin.

64 Pin Pinout

The following table groups the pins by function. It is useful when designing a breakout board, testing with wires, or troubleshooting the connector.

Pin	Signal	Description
01-13	`12V`	Main power `+12V` output
14-26	`GND`	Main power ground
27	`ADR`	PMBus address setting / address related signal
28	`NC`	Not connected
29	`NC`	Not connected
30	`GND`	Signal ground
31	`SCL`	PMBus / SMBus / I2C clock
32	`SDA`	PMBus / SMBus / I2C data
33	`EN`	`#ENABLE`, pull low to enable the main 12V output
34	`IMON`	Current monitor
35	`PSOK`	Power OK / power supply normal status
36	`PRE`	Present, pull high as part of enabling the main output
37	`12VSB`	12V standby power, low current, usually always on
38	`PSIN`	Power supply alarm / status signal
39-51	`GND`	Main power ground
52-64	`12V`	Main power `+12V` output

From this layout, the two ends of the connector are the high-current area, and the middle is the control and management signal area. When designing a PCB, 12V and GND should use large copper pours, many parallel vias, sufficiently wide traces, or copper bars. Signal lines should stay away from high-current switching loops to avoid coupling current ripple and contact noise into the management interface.

Enabling the 12V Main Output

After AC power is applied, a CSPS power supply usually does not immediately enable the high-current 12V main output. To turn on the main output, the PRE and EN signals need to be handled.

Proper Enable Method

Pull PRE, Pin 36, up to 12VSB, Pin 37.
Pull EN, Pin 33, down to signal ground. Pin 30 is recommended.

In practical terms:

PRE tells the power supply that the module has been inserted into the backplane and the system allows it to enter the working state.
EN is an active-low enable signal. Pulling it low turns on the main 12V output.
12VSB can power a control board, MCU, fan controller, or soft-start circuit, but it should not be used as a high-current output.

If using an MCU for control, a safer approach is:

Power the MCU from 12VSB through a DC-DC converter or LDO.
Pull EN down to signal ground through an open-drain output, N-MOS, or optocoupler.
Pull PRE up to 12VSB through a suitable resistor.
After power-on, check status first, then enable EN after a delay.

Quick Test Method

According to the open-source breakout board project, you can also place a resistor between Pin 33 EN and Pin 36 PRE to enable the output. Many people short the pins directly, but using a resistor is recommended instead of a hard short.

This method is suitable for temporary testing, not for a finished power supply intended for long-term operation. For long-term use, it is better to handle the signals as PRE -> 12VSB and EN -> GND, and leave protection and test points for the control signals.

PMBus / SMBus / I2C Management Interface

Pin 31 SCL and Pin 32 SDA are the management bus. Many server power supplies support PMBus internally and can expose or configure status information such as:

Output voltage, current, and power.
Temperature and fan status.
Input voltage status.
Alarm, fault, and protection states.
Manufacturer, model, serial number, and other identification data.

Several details are worth noting:

PMBus is based on SMBus / I2C, but its command set is not the same as an ordinary I2C sensor.
Different power supplies expose different commands. Some commands are read-only, and some may be vendor locked.
ADR may affect the device address, which is useful for multi-PSU parallel or redundant backplanes.
Before connecting an MCU or USB-I2C tool, confirm the bus voltage level. Do not assume it can be connected directly to 5V.
SCL / SDA usually need pull-up resistors. The pull-up voltage and resistance should be decided based on the PSU documentation and measurements.

If you only want to use the PSU as a high-power 12V output, you can leave PMBus disconnected at first and only handle PRE, EN, 12VSB, and GND. If you want to build a full monitoring panel or automatic protection, PMBus becomes very useful.

Breakout Board Design Notes

High-Current Output

Common CSPS power supplies range from several hundred watts to more than one kilowatt. At 12V output:

750W is about 62.5A.
1200W is about 100A.

This is far beyond what ordinary Dupont wires, breadboards, or thin PCB traces can safely carry. When designing a breakout board:

Use large copper pours or copper bars for 12V and GND.
Choose output terminals with sufficient current rating, such as Anderson Powerpole, copper studs, terminal blocks, or XT series high-current connectors.
Connect multiple 12V pins and multiple GND pins. Using only a few contacts can cause overheating.
Add fuses, circuit breakers, or electronic protection to the output.
During long high-current operation, check the temperature rise of connectors, solder joints, and cables.

Control Signals

Control signals should not share long thin return paths with the main current. Recommended practices:

Bring out Pin 30 signal ground separately as the reference ground for the MCU / control board.
Pull EN down with a transistor or MOSFET. Do not let the MCU directly take unknown transients.
Add current limiting, voltage division, or protection before feeding PSOK, PSIN, and IMON into an MCU.
Keep PMBus traces short and place a ground reference nearby.

Cooling and Noise

Server power supplies are designed for rack servers and usually rely on high airflow. When used standalone, common issues include:

Fans can still be noisy at no load or light load.
Connectors and output terminals heat up under high current.
Some models may need a minimum load to stay stable.
Parallel operation requires additional care for current sharing and reverse current.

For a lab supply, place it in a well-ventilated area and add a voltmeter, ammeter, and temperature monitoring at the output. Do not seal it in a small box with no airflow for long-term full-load operation.

Common CSPS Power Supply Models

When searching for CSPS power supplies on the used market, three sets of numbers are often mixed together:

Option Part Number: HPE option number, commonly in the form 503296-B21.
Spare Part Number / SPS: spare part number, commonly in the form 511777-001.
PSU body model: commonly in the form DPS-750RB A, HSTNS-PL18, or PS-2751-7CB-LF.

Do not look at only one number when buying a PSU. It is better to check the power rating, input voltage range, edge connector form, and label model at the same time. The following are common Common Slot / CSPS related models for initial filtering.

HPE Common Slot Option Numbers

Power	Common HPE option number	Common spare / generic numbers	Notes
460W	`503296-B21`	`499249-001`, `511777-001`	460W AC Common Slot Gold Hot Plug
460W	`656362-B21`	`643931-001`, `643954-201`, `660184-001`	460W Common Slot Platinum series
750W	`512327-B21`	`506821-001`, `506822-201`, `511778-001`	750W Common Slot series, common `DPS-750RB`
750W	`593831-B21`	`591556-101`, `591554-001`, `599383-001`	750W Common Slot series
750W	`656363-B21`	`643932-001`, `643955-101`, `660183-001`	750W Common Slot Platinum series
750W	`739254-B21`	`746072-001`, `748281-201`, `742516-001`	750W Common Slot series
750W	`697581-B21`	`697579-001`, `700287-001`, `697554-201`	750W Common Slot Platinum series
1200W	`438202-001` / `438202-002`	`440785-001`	1200W Common Slot series, common `DPS-1200FB`
1200W	`656364-B21`	`643933-001`, `643956-101`, `660185-001`, `643956-201`	1200W Common Slot Platinum series
1500W	`684532-B21`	`684529-001`, `684530-201`, `704604-001`	1500W Common Slot Platinum Plus series

Common Models Seen on PSU Labels

Power range	Common PSU model / code	Common HPE numbers
460W	`DPS-460EB A`, `HSTNS-PD14`, `HSTNS-PL14`	`499249-001`, `499250-101`, `499250-201`, `511777-001`, `503296-B21`
460W	`HSTNS-PL23B`, `PS-2461-6C1-LF`	`591553-001`, `591555-201`, `599381-001`
460W	`DPS-460MB A`, `HSTNS-PL28`, `PS-2461-7C-LF`	`643931-001`, `643954-201`, `660184-001`, `656362-B21`
460W	`HSTNS-PR28-AD`, `HSTNS-PL28-AD`, `7001613-J100`	`746071-001`, `748279-201`, `748279-301`, `742515-001`, `739252-B21`
750W	`DPS-750RB-A`, `HSTNS-PL18`, `HSTNS-PD18`	`506821-001`, `506822-101`, `506822-201`, `511778-001`, `512327-B21`
750W	`HSTNS-PL12`	`449838-001`, `449840-001`, `454353-001`
750W	`DPS-750AB-4 A`, `HSTNS-PD31`	`674890-001`, `666375-101`, `674275-B21`
750W	`DPS-750UB B`, `HSTNS-PD22B`	`591556-101`, `591554-001`, `599383-001`, `593831-B21`
750W	`DPS-750AB-3 A`, `HSTNS-PD29`	`643932-001`, `643955-101`, `660183-001`, `656363-B21`
750W	`HSTNS-PL29-AD`, `PS-2751-7CB-LF`	`746072-001`, `748281-201`, `742516-001`, `739254-B21`
750W	`HSTNS-PL34`, `PS-2751-9C-LF`	`697579-001`, `700287-001`, `697554-201`, `697581-B21`
1200W	`DPS-1200FB A`, `HSTNS-PD11`	`440785-001`, `438202-001`, `438202-002`
1200W	`DPS-1200FB-1 A`, `HSTNS-PD19`	`570451-001`, `570451-101`, `579229-001`
1200W	`DPS-1200SB A`, `HSTNS-PD30`	`643933-001`, `643956-101`, `660185-001`, `643956-201`, `656364-B21`
1200W	`DPS-1200LB C`	`MVKTR-LF`
1500W	`HSTNS-PL33`, `PS-2152-1C-LF`	`684529-001`, `684530-201`, `704604-001`, `684532-B21`
2400W	`DPS-2400AB`	Verify against the specific label

Do Not Confuse It With Flex Slot

HPE later introduced Flex Slot power supplies, such as 500W / 800W / 1400W / 1600W / 1800W-2200W series. Flex Slot is also a hot-plug server PSU form factor, but it is smaller than the previous Common Slot generation, and the connector and breakout board are usually not directly compatible. This article mainly covers the 64 pin edge connector Common Slot / CSPS type. Do not assume that any hot-plug server PSU can use the same breakout board.

Some Huawei server power supplies have an appearance and connector that are very close to HP Common Slot, but not all Huawei hot-plug 12V power supplies should be classified as CSPS. Many previously mentioned PAC*, PDC*, EPW*, PHD*, and TPS* models are simply server hot-plug PSU series. Their connector size, control pins, and startup logic may not match HP 64 pin Common Slot.

At present, the following model can be listed more confidently as Huawei-related CSPS / Common Slot form factor:

Model	Manufacturer	Huawei part number / related marking	Common systems	Specification	Notes
`PS-2122-3H`	Lite-On	`02130985`, `WEPW12K00`, sometimes written as `PS-2L22-3H`	Often seen in used Huawei X6000, RH1288 V2/V3, RH2288 V2/V3 parts	1200W, `+12V 100A`, `+12VSB 2.5A`	Documentation and used-parts listings both point to a 1200W 12V hot-plug module used in Huawei servers, with an appearance close to Common Slot PSUs

The output capability of PS-2122-3H depends on the input voltage range. Common markings are:

100V input: +12V 62.5A, about 750W.
110-127V input: +12V 75A, about 900W.
200-240V AC or 240V DC input: +12V 100A, about 1200W.
Standby output: +12VSB 2.5A.

Huawei EPW750-12A type 750W power supplies are often compared with HP DPS-750RB A. They also have an edge connector, 12V main output, and 12VSB, and there is a user report that HP DPS-750RB A worked in a Huawei RH2288H V3. However, this is more like a clue from physical appearance and partial compatibility testing, and it is not enough to put EPW750-12A into the confirmed CSPS model table. A safer description is: treat it as a model to be verified, and confirm the edge connector pinout, enable logic, and PMBus behavior before use.

The following Huawei power supplies should not currently be written directly as CSPS-compatible models:

PAC550S12-BE
PAC900S12-BE
PAC1500S12-BE
PAC2000S12-BE
PAC2000S12-TE
EPW3000-12A
PHD3000S12-CE
TPS2500-12D
PDC1200S12-CE

They are all common Huawei server / telecom equipment 12V hot-plug power supplies, but “hot-plug 12V power supply” does not mean “HP Common Slot / CSPS pinout compatible.” If clear edge connector photos, original pinout tables, or measured pinouts are found later, they can be added to the confirmed table separately.

In theory, Common Slot power supplies with the same 64 pin edge connector and the same pinout may be compatible. However, used power supplies can come from many sources and may have vendor-specific firmware, different power ratings, different fan policies, or different management commands. Before actual use, it is best to verify with low risk:

Apply only AC input with no load, and confirm whether 12VSB is normal.
Handle PRE / EN with a resistor method, and confirm whether the main 12V starts.
Add a small load and test voltage stability.
Increase the load gradually while observing temperature rise, fan behavior, and protection behavior.

Summary

The core idea of CSPS / Common Slot server power supplies is straightforward:

Many pins at both ends are paralleled for 12V and GND.
A small number of middle pins handle enable, status, standby power, and PMBus management.
The main output requires PRE and EN to work together before it turns on.
12VSB is standby power for control circuitry, not the main output.
The real difficulty is not “turning it on,” but high-current connection, cooling, protection, and long-term reliability.

For a simple breakout board, at minimum you need to connect 12V, GND, 12VSB, PRE, and EN. For a complete backplane, SCL, SDA, ADR, PSOK, IMON, and PSIN should also be brought out for later monitoring and automatic control.

References

Common CSPS Power Supply Models

When searching for CSPS power supplies on the used market, three sets of numbers are often mixed together:

Option Part Number: HPE option number, commonly in the form 503296-B21.
Spare Part Number / SPS: spare part number, commonly in the form 511777-001.
PSU body model: commonly in the form DPS-750RB A, HSTNS-PL18, or PS-2751-7CB-LF.

HPE Common Slot Option Numbers

Power	Common HPE option number	Common spare / generic numbers	Notes
460W	`503296-B21`	`499249-001`, `511777-001`	460W AC Common Slot Gold Hot Plug
460W	`656362-B21`	`643931-001`, `643954-201`, `660184-001`	460W Common Slot Platinum series
750W	`512327-B21`	`506821-001`, `506822-201`, `511778-001`	750W Common Slot series, common `DPS-750RB`
750W	`593831-B21`	`591556-101`, `591554-001`, `599383-001`	750W Common Slot series
750W	`656363-B21`	`643932-001`, `643955-101`, `660183-001`	750W Common Slot Platinum series
750W	`739254-B21`	`746072-001`, `748281-201`, `742516-001`	750W Common Slot series
750W	`697581-B21`	`697579-001`, `700287-001`, `697554-201`	750W Common Slot Platinum series
1200W	`438202-001` / `438202-002`	`440785-001`	1200W Common Slot series, common `DPS-1200FB`
1200W	`656364-B21`	`643933-001`, `643956-101`, `660185-001`, `643956-201`	1200W Common Slot Platinum series
1500W	`684532-B21`	`684529-001`, `684530-201`, `704604-001`	1500W Common Slot Platinum Plus series

Common Models Seen on PSU Labels

Power range	Common PSU model / code	Common HPE numbers
460W	`DPS-460EB A`, `HSTNS-PD14`, `HSTNS-PL14`	`499249-001`, `499250-101`, `499250-201`, `511777-001`, `503296-B21`
460W	`HSTNS-PL23B`, `PS-2461-6C1-LF`	`591553-001`, `591555-201`, `599381-001`
460W	`DPS-460MB A`, `HSTNS-PL28`, `PS-2461-7C-LF`	`643931-001`, `643954-201`, `660184-001`, `656362-B21`
460W	`HSTNS-PR28-AD`, `HSTNS-PL28-AD`, `7001613-J100`	`746071-001`, `748279-201`, `748279-301`, `742515-001`, `739252-B21`
750W	`DPS-750RB-A`, `HSTNS-PL18`, `HSTNS-PD18`	`506821-001`, `506822-101`, `506822-201`, `511778-001`, `512327-B21`
750W	`HSTNS-PL12`	`449838-001`, `449840-001`, `454353-001`
750W	`DPS-750AB-4 A`, `HSTNS-PD31`	`674890-001`, `666375-101`, `674275-B21`
750W	`DPS-750UB B`, `HSTNS-PD22B`	`591556-101`, `591554-001`, `599383-001`, `593831-B21`
750W	`DPS-750AB-3 A`, `HSTNS-PD29`	`643932-001`, `643955-101`, `660183-001`, `656363-B21`
750W	`HSTNS-PL29-AD`, `PS-2751-7CB-LF`	`746072-001`, `748281-201`, `742516-001`, `739254-B21`
750W	`HSTNS-PL34`, `PS-2751-9C-LF`	`697579-001`, `700287-001`, `697554-201`, `697581-B21`
1200W	`DPS-1200FB A`, `HSTNS-PD11`	`440785-001`, `438202-001`, `438202-002`
1200W	`DPS-1200FB-1 A`, `HSTNS-PD19`	`570451-001`, `570451-101`, `579229-001`
1200W	`DPS-1200SB A`, `HSTNS-PD30`	`643933-001`, `643956-101`, `660185-001`, `643956-201`, `656364-B21`
1200W	`DPS-1200LB C`	`MVKTR-LF`
1500W	`HSTNS-PL33`, `PS-2152-1C-LF`	`684529-001`, `684530-201`, `704604-001`, `684532-B21`
2400W	`DPS-2400AB`	Verify against the specific label

Do Not Confuse It With Flex Slot

At present, the following model can be listed more confidently as Huawei-related CSPS / Common Slot form factor:

Model	Manufacturer	Huawei part number / related marking	Common systems	Specification	Notes
`PS-2122-3H`	Lite-On	`02130985`, `WEPW12K00`, sometimes written as `PS-2L22-3H`	Often seen in used Huawei X6000, RH1288 V2/V3, RH2288 V2/V3 parts	1200W, `+12V 100A`, `+12VSB 2.5A`	Documentation and used-parts listings both point to a 1200W 12V hot-plug module used in Huawei servers, with an appearance close to Common Slot PSUs

The output capability of PS-2122-3H depends on the input voltage range. Common markings are:

100V input: +12V 62.5A, about 750W.
110-127V input: +12V 75A, about 900W.
200-240V AC or 240V DC input: +12V 100A, about 1200W.
Standby output: +12VSB 2.5A.

The following Huawei power supplies should not currently be written directly as CSPS-compatible models:

PAC550S12-BE
PAC900S12-BE
PAC1500S12-BE
PAC2000S12-BE
PAC2000S12-TE
EPW3000-12A
PHD3000S12-CE
TPS2500-12D
PDC1200S12-CE

Apply only AC input with no load, and confirm whether 12VSB is normal.
Handle PRE / EN with a resistor method, and confirm whether the main 12V starts.
Add a small load and test voltage stability.
Increase the load gradually while observing temperature rise, fan behavior, and protection behavior.

Summary

The core idea of CSPS / Common Slot server power supplies is straightforward:

Many pins at both ends are paralleled for 12V and GND.
A small number of middle pins handle enable, status, standby power, and PMBus management.
The main output requires PRE and EN to work together before it turns on.
12VSB is standby power for control circuitry, not the main output.
The real difficulty is not “turning it on,” but high-current connection, cooling, protection, and long-term reliability.

PMBus on KnightLi Blog

CSPS Common Slot Server Power Supply Interface and Pinout

Interface Structure

64 Pin Pinout

Enabling the 12V Main Output

Proper Enable Method

Quick Test Method

PMBus / SMBus / I2C Management Interface

Breakout Board Design Notes

High-Current Output

Control Signals

Cooling and Noise

Common CSPS Power Supply Models

HPE Common Slot Option Numbers

Common Models Seen on PSU Labels

Do Not Confuse It With Flex Slot

Huawei / xFusion Related Models

Summary

References

Common CSPS Power Supply Models

HPE Common Slot Option Numbers

Common Models Seen on PSU Labels

Do Not Confuse It With Flex Slot

Huawei / xFusion Related Models

Summary

References