Summary of SCSI Protocols and Transfer Modes
Reprinted, with permission, from The PC Guide
Summary of SCSI Protocols and Transfer Modes
For easier comparison, the chart below shows all of the different SCSI transfer modes and feature sets, along with their key characteristics. For your clicking pleasure, I've also hyperlinked everything that wasn't nailed down ;^)
Signaling Method |
Maximum Devices Per Bus |
Maximum Cable Length (m) |
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8 |
5 |
5 |
8 |
6 |
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8 |
25 |
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16 |
5 |
10 |
16 |
6 |
|||||
16 |
25 |
||||||||
8 |
10 |
10 |
8 |
3 |
|||||
8 |
25 |
||||||||
16 |
10 |
20 |
|
16 |
3 |
||||
16 |
25 |
||||||||
8 |
20 |
20 |
8 |
1.5 |
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4 |
3 |
||||||||
8 |
25 |
||||||||
16 |
20 |
40 |
8 |
1.5 |
|||||
4 |
3 |
||||||||
16 |
25 |
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8 |
40 |
40 |
8 |
12 |
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2 |
25 |
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8 |
25 |
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16 |
40 |
80 |
16 |
12 |
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2 |
25 |
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16 |
25 |
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16 |
40 (DT) |
160 |
16 |
12 |
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2 |
25 |
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16 |
40 (DT) |
160 |
16 |
12 |
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2 |
25 |
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16 |
40 (DT) |
160 |
16 |
12 |
|||||
2 |
25 |
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16 |
80 (DT) |
320 |
Fast-160, ? |
16 |
12 |
||||
2 |
25 |
Some notes on this table:
- "(DT)" means that transfer mode uses double transition clocking.
- Throughput numbers are in decimal megabytes per second.
- To keep the table from getting cluttered, I've only mentioned current cabling, not obsolete cables.
- The number of devices includes the host adapter.
- For Ultra and faster speeds, the maximum length of cable for some signaling types depends on the number of devices on the chain; thus, the multiple rows.
- Ultra320 specifications are not final as of this writing.
Note: The number of
devices (8 or 16) includes the host adapter.
Next: SCSI Host
Adapters