I have a couple of old computers. Some of them have a SCSI-1 or SCSI-2 interface over an internal 50 pin IDC connector or an external DB25. Now I want to connect something to them, in particular a hard drive. One option is to get a "modern" hard drive.
I have heard that parallel SCSI is backwards compatible, so given the right adapter it should be possible to connect an Ultra-320 SCSI hard drive to a SCSI-1 platform. A comment to this question mentions that it is almost correct that SCSI is completely backwards compatible and that a new question should be asked concerning the details. This is that question.
(Please note that this question is not about SCSI-to-CF/SD adapters, it's not a generic "how to add storage to an old platform".)
- Bus width
The old systems use an 8 bit bus, but a lot of the newer SCSI devices are listed as having a 16 bit bus. What happens there? Will the device figure out that my host can only use 8 bits?
There seems to be a few different electrical standards: Single-ended, LVD, HVD. Presumably an adapter needs to convert between them. Is it possible? How do I know which is being used by the device? Wikipedia has this to say:
Different SCSI standards use the same SCSI connectors as in HVD and LVD SCSI (High Voltage Differential and Low Voltage Differential) . HVD uses 15V while LVD uses 3.3V, so connecting an HVD device to an LVD host bus adaptor can blow the line drivers on the HBA, likewise an HVD HBA connected to an LVD device.
- Device size
I know that a lot of file system drivers on the host side will have issues with larger disk sizes, and this question is not about that, but will the SCSI-1 command set at least be able to figure out that the device on the other end is indeed a super-mega-unheard-of large block device of several hundred gigabytes? That is - would a correctly implemented SCSI-1 hard drive driver with no arbitrary limits be able to interrogate and access the full size of a modern SCSI device?
What do I have to do, know, or find out if I want to connect an Ultra-320 SCSI hard drive to a SCSI-1 computer from the late eighties or early nineties?