SCSI question: what's u, w, uw, u2w, u160???????

[Hahah307]

Can anyone explain these different types of SCSI to me? Please.....?

 

[pdo]

I don't know too. All these U-W, FAST, UltraWide shat so confusing. But you can check this out.

 

[Bronko]

They basically represent different implementations of SCSI.

U = Ultra
W = Wide
UW = Yep, you guessed it Ultra Wide (40 Mb/s)
U2W = Ultra 2 Wide (80 Mb/s)
U160 = Ultra 160 (160 Mb/s)

If you go to www.adaptec.com, you should be able to find a SCSI primer without to much difficulty.

 

[Ben]

Wide SCSI 10MB/S

Fast Wide SCSI 20MB/S
(aka Ultra SCSI)

Ultra Wide SCSI 40MB/S

Ultra2 Wide LVD SCSI 80MB/S

Ultra160 Wide SCSI 160MB/S


LVD=Low Voltage Differential

 

[andylawcc]

are they pin compatible with each other?

 

[Ben]

Not all of them.

Ultra SCSI uses the 50-pin connectors and the flat ribbon cable that resembles the IDE cables.

Ultra Wide SCSI uses the 68-pin connectors with the flat cable. This looks more like a DMA66 cable with 68-pin high density connectors.

Ultra2, Ultra160, and Ultra320, all use the woven ribbon LVD cables with the 68-pin connectors.

SCSI is getting much better at retaining backward compatability. The last 4 generations have used the 68-pin connectors and the last 3 have used the same cable. All of the 68-pin drives will function on all the 68-pin controllers, but there are data transfer speed issues with mixing unlike protocols.
I/O Guide
Connector Chart
Typical SCSI bus

 

[MereMortal]

Things are a bit more complicated, actually. SCSI protocols are defined not only by maximum throughput, but also by bus size. One thing to keep in mind is that 'wide' corresponds to a 16 bit bus,
whereas 'narrow' corresponds to an 8 bit bus. So two standards with
the same max throughput, say ultra and fast wide, will need different connectors.

Here's a list:
SCSI1: 5 MB/s, 8 bit
SCSI2: 5 MB/s, 8 bit
SCSI2 wide: 10MB/s, 16 bit
SCSI2 fast: 10MB/s, 8 bit
SCSI2 fast wide: 20MB/s, 16 bit
ultra: 20MB/s, 8 bit
ultra wide: 40MB/s, 16 bit
ultra2: 40MB/s, 8 bit (never implemented in hardware)
ultra2 wide: 80 MB/s, 16 bit
ultra160: 160 MB/s, 16bit (part of ultra3 standard)

 

[andylawcc]

what's with the 50 pin one (after reading adaptec's chart, thx Ben anyways)
It belongs to Ultra2 Wide too which also has 68 pin?

and a Adaptec PCI SCSI controller card (or any SCSI card),
I can USUALLY connect 3+3+1 SCSI device right?

 

[Ben]

Sorry, I'm not too clear on what your asking.