IBM Support

SCSI Devices - Current Draw

Troubleshooting


Problem

SCSI-equipped PC systems have limitations to the amount of +5V and +12V current available from the power supplies. These limits differ from system to system. The Tables below list both the current limits by system type, but also the amount of current draw

Resolving The Problem

SCSI-equipped PC systems have limitations to the amount of +5V and +12V current available from the power supplies. These limits differ from system to system. The Tables below list both the current limits by system type, but also the amount of current drawn by various IBM SCSI devices. By totaling up the current draw for all devices used, and planned to be added, you can determine whether your PS/2 can handle the total power draw. (While the diskette drives listed below are not SCSI, they must be included in the total current draw calculations.)

Note 1: If the total amount of nominal operating voltage for either the 5V or 12V line required exceeds the available current available from the power supply you run the risk of the system shutting down.

Note 2: SCSI devices installed in external storage cabinets (like the IBM 3510 and 3511), and external self-powered drives (such as the 3440/3445/3450 Tape Drives) do not draw power from the system power supply, and therefore need not be included in the total. However, the 3511 itself has a power supply as the PS/2 Model 95, and therefore has limitations as well.

Note 3: Not all devices listed below can be used in all PS/2 systems. Refer to the system and device announcement letters for compatibility information. the 3511 expansion unit itself, which contains 7 SCSI drive bays, has the same power limitations as the PS/2 Model 95.

Current Draw by Device

Device Type Device +5V Draw +12V Draw
CD-ROM Drives CD-ROM Drive I 1 1.8
CD-ROM Drives CD-ROM Drive II 1 1
Diskette Drives 3.5" Enhanced 2.88MB Diskette Drive 0.6 N/A
Diskette Drives 5.25" 1.2MB Diskette Drive 0.9 1
Diskette Drives 5.25" Slim High 1.2MB Diskette Drive 0.3 0.5
Hard Disk Drives 60MB SCSI Hard Disk Drive 0.66 1
Hard Disk Drives 80MB SCSI Hard Disk Drive 0.5 0.8
Hard Disk Drives 104/208/212MB SCSI Hard Disk Drive 0.57 0.63
Hard Disk Drives 120MB SCSI Hard Disk Drive 0.66 1
Hard Disk Drives 160MB SCSI Hard Disk Drive 0.5 0.8
Hard Disk Drives 320MB SCSI Hard Disk Drive 0.66 1
Hard Disk Drives 400MB SCSI Hard Disk Drive 0.66 1
Hard Disk Drives 540MB Fast SCSI-2 Hard Disk Drive 1.16 0.78
Hard Disk Drives 1GB Fast SCSI-2 Hard Disk Drive (P/N 32G4198) 1.1 0.4
Hard Disk Drives 1GB SCSI Hard Disk Drive(P/N 6451052) 1.1 0.8
Hard Disk Drives 2GB SCSI Hard Disk Drive(P/N 32G4336) 1.1 0.8
Hard Disk Drives 2GB SCSI-2 Fast/Wide Hard Disk Drive (P/N 32G3796) 1.1 0.8
Magneto Optical (MO) Drives 3.5" Enhanced Rewritable Optical Drive 0.9 1.4
Magneto Optical (MO) Drives 3.5" Rewritable Optical Drive 0.9 1.4
Tape Drives 2GB Half-High SCSI Tape Drive 0.45 0.17
Tape Drives 2.3GB Full-High SCSI Tape Drive 2 0.4

Total Allowable Current Draw by System Type
System Machine Type +5V Draw +12V Draw
PS/2 85xx Systems 8556 (118W PS) 2.71 2.8
PS/2 85xx Systems 8557 (197W PS) 5 4.5
PS/2 85xx Systems 8565 (250W PS) 3 5
PS/2 85xx Systems 8580 (225W/242W PS) 3 5
PS/2 85xx Systems 8590 (194W PS) 2.3 3.2
PS/2 85xx Systems 8595 (329W/335W PS) 4.6 7.5
PS/2 95xx Systems 9553 (118W PS) 2.71 2.8
PS/2 95xx Systems 9556 (118W PS) 2.71 2.8
PS/2 95xx Systems 9557 (197W PS) 5 4.5
PS/2 95xx Systems 9576 (118W PS) 2.71 2.8
PS/2 95xx Systems 9577 (197W PS) 5 4.5
PS/2 95xx Systems 9585 (288W PS) 6 6.99
PS/2 95xx Systems 9590 (194W PS) 4 4.7
PS/2 95xx Systems 9595 (335W PS) 4.6 7.5
PS/2 95xx Systems 9595 (400W PS) 8 7
PS/2 Expansion Units 3511-003 Expansion Unit (335W PS) 4.6 7.5
PS/2 Expansion Units 3511-0V0 Expansion Unit (400W PS) 8 7

Document Location

Worldwide

Operating System

System x Hardware Options:All operating systems listed

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Document Information

Modified date:
29 January 2019

UID

ibm1MIGR-63270

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