SCSI SCSI SCSI & MO SCSI questions (basic)

[redrumloa]

Ok refresh my memory, please:-)

1)The whole SCSI chain is as slow as it's slowest device, correct right? So if you put a narow CD-ROM on the same chain as UW devices they will all work as narrow devices?

2) 80 pin SCA devices work just fine on cybscsi.device with a 80->68 pin adapter. Correct?

I'll add a couple more questions if I think of it, thanks in advance:-)

[PaSha]

redrumloa wrote:
Ok refresh my memory, please:-)

1)The whole SCSI chain is as slow as it's slowest device, correct right? So if you put a narow CD-ROM on the same chain as UW devices they will all work as narrow devices?

Wrong. You will always achieve maximum possible speed. Between two UW-SCSI units (harddrives, the cybppc.device), transfer is done at full UW-SCSI speed, 40 MB/s. But between a FastSCSI unit (like a cdrom drive) and a UW-SCSI unit, transfer will be done at FastSCSI speeds, 10 MB/s.

2) 80 pin SCA devices work just fine on cybscsi.device with a 80->68 pin adapter. Correct?

I'll add a couple more questions if I think of it, thanks in advance:-)

Well, they'll work perfectly on cybppc.device , this is the device name of the CS-PPC/mk3 UW-SCSI controller, and I'm assuming this is the controller you mean.

It won't work on cybscsi.device (CS mk2) since this is a 50-pin controller ;-)

Anyways, best of luck with your CS-PPC

regards,
Paul

[gwalp]

 
This is of course as long as the Fast SCSI is at the end of the chain.  cyperstorm board -> UW SCSI -> UW SCSI -> FAST SCSI.  If the FAST SCSI is in betweeen two UW SCSI devices transfer would not be at UW SCSI rate.
You can even have
 UW SCSI -> cyperstorm board -> UW SCSI-> Fast SCSI.
 Fast SCSI -> Cyperstorm board ->UW SCSI->UW SCSI.
The Cyperstrom MK III does not have active termination even if the board is the last device you need to add active ternination after the board and at the other end of the chain.

gwalp  

[PaSha]

gwalp wrote:
 
This is of course as long as the Fast SCSI is at the end of the chain.  cyperstorm board -> UW SCSI -> UW SCSI -> FAST SCSI.  If the FAST SCSI is in betweeen two UW SCSI devices transfer would not be at UW SCSI rate.

No offence, but this is nonsense.
SCSI transfer will always be at the maximum possible rate of the units transferring, regardless of what devices might be in between. This is what makes SCSI better than IDE :-)

If you utilize passive 68-50 pin adapters for your CD-ROM drives and other narrow SCSI units (passive as in not terminating the 8 Wide bits) you can stick them anywhere in the chain without affecting performance.
But if you use active 68-50 pin adapters (terminating the 8 Wide bits) you will obviously have to stick the narrow devices in the end of the chain.

You can even have
 UW SCSI -> cyperstorm board -> UW SCSI-> Fast SCSI.
 Fast SCSI -> Cyperstorm board ->UW SCSI->UW SCSI.
The Cyperstrom MK III does not have active termination even if the board is the last device you need to add active ternination after the board and at the other end of the chain.

gwalp  

Yes, this is correct. A good way to do this is to get two active passthrough terminators, and terminate the controller as one end, and the end of the chain with the other terminator. Make sure at least one unit supplies Term-Power.

-Paul