Power Macintosh G3, G4: Differences Between Available SCSI Cards

This article lists SCSI cards available for Power Macintosh G3 (Blue and White) and Power Mac G4 computers.


The three Apple SCSI cards available as configure-to-order options are as follows, with a shortened name in parentheses:

• Ultra SCSI PCI Card (Ultra)
• Single Channel Ultra2 LVD SCSI Card (Single)
• Dual Channel Ultra2 LVD SCSI Card (Dual) version 1 and 2

The version 2 dual channel SCSI card is functionally equivalent to the version 1 card, though it has been tested and approved for use with the Power Mac G4 (AGP Graphics) computer. Refer to the table below for specific technical information. The card is based on the ATTO ExpressPCI UL2D card. You may refer to the ATTO Web site at http://www.attotech.com for more information about the card.

Table 1 differentiates the various Apple cards based on their features. The Ultra card is best used for connecting slower, legacy SCSI-1 and SCSI-2 devices such as tape drives, hard drives, and scanners, as well as Ultra Narrow SCSI devices.

While there is some overlap among the cards, make purchase decisions based on what type of device you intend to connect to the card.

Specification	Ultra SCSI Card	Single Channel Card	Dual Channel Card version 1	Dual Channel version 2
Supported Computer	Power Macintosh G3 (Blue and White) and Power Mac G4	Power Macintosh G3 (Blue and White)	Power Macintosh G3 (Blue and White)	Power Mac G4 (AGP Graphics)
Max. Transfer Rate (MB/Sec)	20	80	80 per channel	80 per channel
Apple Supported Types	SCSI-1, SCSI-2 (Fast), Ultra Narrow	Ultra2 LVD	Channel A: SCSI-1, SCSI-2 (Fast), Ultra Narrow, Ultra Wide, Ultra2 LVD Channel B: Ultra2 LVD	Channel 1: SCSI-1, SCSI-2 (Fast), Ultra Narrow, Ultra Wide, Ultra2 LVD Channel 2: Ultra2 LVD
Internal Connector	50-pin standard (plug) (Not Apple Supported)	68-pin high-density Ultra2 (socket)	Channel A: 68-pin high-density Ultra2 (socket) Channel B: 68-pin high-density Ultra2 (socket), and 50-pin standard (plug) *	Channel 2: 68-pin high-density Ultra2 (socket)
External Connector	50-pin high-density (socket) Includes a high density 50-pin to DB25 adapter	68-pin high-density Ultra2 (socket)	Channel A: 68-pin high-density Ultra2 (socket) **	Channel 1: 68-pin VHDCI Ultra2 (socket)
Max. Devices Int/Ext	Up to 7 total	Up to 15 total	Up to 30 total	Up to 30 total
Maximum Cable Length Internal/External	3 m with non-Ultra devices; 1.5 m with Ultra devices or a mix of Ultra and non-Ultra devices	12 m with only Ultra2 LVD devices	Channel A: 3 m with non-Ultra devices; 1.5 m with Ultra devices or a mix of Ultra and non-Ultra devices; 12 m with only Ultra2 LVD devices Channel B: 12 m with only Ultra2 LVD devices	Channel 1: 3 m with non-Ultra devices; 1.5 m with Ultra devices or a mix of Ultra and non-Ultra devices; 12 m with only Ultra2 LVD devices Channel 2: 12 m with only Ultra2 LVD devices
PCI System Bus	32 bit	32 bit	64 bit	64 bit
Driver Compatibility	Compatible with SCSI Manager 4.3, and earlier drivers	Requires SCSI Manager 4.3 compliant driver	Requires SCSI Manager 4.3 compliant driver	Requires SCSI Manager 4.3 compliant driver

Table 1 Apple SCSI Card Specifications

* For maximum performance, the internal connector (Channel B) is recommended for Ultra2 devices only.

** The internal/external (Channel A) connectors are recommended for use with all SCSI types.

All three Apple SCSI cards allow the Power Macintosh G3 (Blue and White) to start up from an attached device that has appropriate system software installed.

Maximum throughput (Ultra2) is possible only when Ultra2 devices are on the SCSI bus. When you connect a non-Ultra2 device to the single or dual channel card, the SCSI manager negotiates with each device for maximum speed for that particular device.

Definitions

Additional definitions may be found at the following Web sites:

http://www.seagate.com/support/kb/disc/scsirev.html

http://www.adaptec.com/tools/glossary/general.html

Notes

1. The term Low Voltage Differential (LVD) can be used interchangeably with the term Ultra2.
2. High Voltage Differential devices, also known as Differential devices, are not compatible.
3. With regard to the Ultra2 LVD SCSI cards, there are adapters to connect a Narrow device to the Wide bus, but this may severely affect performance. Using such an adapter is not recommended or supported.
4. Though Apple SCSI cards may be similar to certain Adaptec cards, use only Apple SCSI Card Firmware Updates on Apple cards. Do not use Apple Firmware Updates on Adaptec Power Domain cards. Similar firmware updates for Adaptec SCSI cards may be available from Adaptec.
5. For more information on the Apple Ultra SCSI PCI Card, see the following article:
Article 58245: "About Your Ultra SCSI PCI Card"

This article provides information about a non-Apple product. Apple, Inc. is not responsible for its content. Please contact the vendor for additional information.

The following article can help you search for a particular vendor's address and phone number:
Article 17159: "Locating Vendor Information"