As you may have seen, I previously did a writeup on Indy power supplies. I've recently examined the SGI Indigo 2 PSU, and while I won't be exploring it in the same level of detail as the Indy I wanted to share some of the basics.
If referencing or duplicating this information, I ask that you maintain a prominent link to this original forum post for further updates, as well as a credit by name.
Non-Impact
Power is supplied over two 18-pin single row 3.96mm connectors, with non-keyed male pin header on the motherboard side. I will refer to them as the Left Hand and Right Hand connectors from the perspective facing the power supply, as outlined in the picture below.
There is an additional AMP / TE Mate-N-Lock (a.k.a. disk drive "Molex connector") supplying +5/+12V for the disk backplane. The pin configuration on this is standard, as on modern PCs.
The Left Hand connector pins are as follows:
The Right Hand connector pins are as follows:
The model number under test is an ITT PowerSystems PEC4074, with the following output ratings:
The Indigo 2 power supply (like the Indy PSU) is Ground to Stop on pin 11 of the Right Hand connector. This means that properly functioning Indigo 2 (non-impact) power supplies will start up on their own if unplugged from the motherboard and given AC line power. However they will want at bare minimum load on their +5V rail to enter proper regulation. Be advised that testing an Indigo 2 power supply without load is unlikely to yield meaningful results.
The +5V rail can be increased in voltage (+0.3V) or decreased in voltage (-0.2V) by a register on the SGI HPC3 PBUS, interacting with the Left Hand pin 3 (MH) and pin 4 (ML). These are fixed voltage increments controlled fully by software, with no analog voltage sense feedback. See post #6 for more information.
The SGI Vault M is an external SCSI disk enclosure based on the Indigo 2 chassis, and uses the Indigo 2 PSU to power the disks inside. It achieves PSU stability by presenting 1 Ohm of resistance on the +5V rail, for 25W of power draw. This is the notorious "heater cage" in the enclosure, which is also present in the picture above.
Standby power usage was 5.5622W when switched soft-off via the Run line.
Like the Indy power supply it appears to have no power factor correction, and exhibited a dismal -0.57 (capacitive) Power Factor under load.
If referencing or duplicating this information, I ask that you maintain a prominent link to this original forum post for further updates, as well as a credit by name.
Non-Impact
Power is supplied over two 18-pin single row 3.96mm connectors, with non-keyed male pin header on the motherboard side. I will refer to them as the Left Hand and Right Hand connectors from the perspective facing the power supply, as outlined in the picture below.
There is an additional AMP / TE Mate-N-Lock (a.k.a. disk drive "Molex connector") supplying +5/+12V for the disk backplane. The pin configuration on this is standard, as on modern PCs.
The Left Hand connector pins are as follows:
Pin # | Wire Color | Function |
---|---|---|
1 | Black | 0V |
2 | Black | 0V |
3 | White | "MH" / Motherboard Higher (?) - raises 5V rail by 0.3V |
4 | White | "ML" / Motherboard Lower (?) - lowers 5V rail by 0.2V |
5 | Red / White | +5V standby |
6 | Red | +5V |
7 | Red | +5V |
8 | Red | +5V |
9 | Red | +5V |
10 | N/C | |
11 | Red | +5V |
12 | Red | +5V |
13 | Red | +5V |
14 | Red | +5V |
15 | Black | 0V |
16 | Black | 0V |
17 | Black | 0V |
18 | Black | 0V |
The Right Hand connector pins are as follows:
Pin # | Wire Color | Function |
---|---|---|
1 | Black | 0V |
2 | Black | 0V |
3 | Black | 0V |
4 | Black | 0V |
5 | Yellow | +3.3V |
6 | Yellow | +3.3V |
7 | Yellow | +3.3V |
8 | Blue | -5V |
9 | White | Power good signal |
10 | Violet | -12V |
11 | White | Run (Ground to stop) |
12 | Orange | +12V |
13 | Orange | +12V |
14 | N/C | |
15 | Black | 0V |
16 | Black | 0V |
17 | Black | 0V |
18 | Black | 0V |
The model number under test is an ITT PowerSystems PEC4074, with the following output ratings:
Rail | Rating |
---|---|
+5V | 40A |
+12V | 12A |
-12V | 1A |
+3.3V | 12A |
-5V | 1A |
+5V standby | 1A |
The Indigo 2 power supply (like the Indy PSU) is Ground to Stop on pin 11 of the Right Hand connector. This means that properly functioning Indigo 2 (non-impact) power supplies will start up on their own if unplugged from the motherboard and given AC line power. However they will want at bare minimum load on their +5V rail to enter proper regulation. Be advised that testing an Indigo 2 power supply without load is unlikely to yield meaningful results.
The +5V rail can be increased in voltage (+0.3V) or decreased in voltage (-0.2V) by a register on the SGI HPC3 PBUS, interacting with the Left Hand pin 3 (MH) and pin 4 (ML). These are fixed voltage increments controlled fully by software, with no analog voltage sense feedback. See post #6 for more information.
The SGI Vault M is an external SCSI disk enclosure based on the Indigo 2 chassis, and uses the Indigo 2 PSU to power the disks inside. It achieves PSU stability by presenting 1 Ohm of resistance on the +5V rail, for 25W of power draw. This is the notorious "heater cage" in the enclosure, which is also present in the picture above.
Standby power usage was 5.5622W when switched soft-off via the Run line.
Like the Indy power supply it appears to have no power factor correction, and exhibited a dismal -0.57 (capacitive) Power Factor under load.
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