Replacing SCSI with IDE

[seabat]

I have a Tyan Tahoe 2 motherboard this is running the floppy disk. The
hard drive (Seagate 2gb) and the CD-ROM are run off a SCSI PCI card.
The CD-ROM is about to crap-out on me and I was wondering if I can
pull it out and then enable one or both of the IDE interfaces in the
BIOS and then hook-up an IDE CD-ROM unit?

If this is possible, would I have to reposition the hard drive on the
SCSI cable, or just unplug the CD-ROM and run? I might have to sneak
into the SCSI BIOS and disable the CD-ROM in there, huh?

 

[Ian Harding]

I have a Tyan Tahoe 2 motherboard this is running the floppy disk. The
hard drive (Seagate 2gb) and the CD-ROM are run off a SCSI PCI card.
The CD-ROM is about to crap-out on me and I was wondering if I can
pull it out and then enable one or both of the IDE interfaces in the
BIOS and then hook-up an IDE CD-ROM unit?

If this is possible, would I have to reposition the hard drive on the
SCSI cable, or just unplug the CD-ROM and run? I might have to sneak
into the SCSI BIOS and disable the CD-ROM in there, huh?

Is the CD-ROM at the end of the cable? If it is then you will need to
connect the hard drive to the end connector and enable termination on
the drive. If the drive does not support termination, leave it where it
is and buy a terminator to plug in to the connector the CD-ROM is
currently on. The SCSI host adapter will probably auto detect the
configuration changes when you boot, but if it's very old you might need
to manually enter the SCSI BIOS setup and remove the CD-ROM entry.

You will need to enable the on-board IDE interface that you plug the new
CD-ROM drive into. You will also need to set the boot order in the
motherboard BIOS setup if you want to be able to boot from CD-ROM.

Ian

 

[GEO Me]

I have a Tyan Tahoe 2 motherboard this is running the floppy disk. The
hard drive (Seagate 2gb) and the CD-ROM are run off a SCSI PCI card.
The CD-ROM is about to crap-out on me and I was wondering if I can
pull it out and then enable one or both of the IDE interfaces in the
BIOS and then hook-up an IDE CD-ROM unit?
If this is possible, would I have to reposition the hard drive on the
SCSI cable, or just unplug the CD-ROM and run? I might have to sneak
into the SCSI BIOS and disable the CD-ROM in there, huh?

It depends on your SCSI card. My BusLogic would allow doing what you
suggested.: unplug the CD-ROM, enable IDE (if needed), and plug an IDE
CD-ROM. (auto....?) Find the specs for your SCSI card.

HTH
Geo

 

[John R Weiss]

The CD-ROM is about to crap-out on me and I was wondering if I can
pull it out and then enable one or both of the IDE interfaces in the
BIOS and then hook-up an IDE CD-ROM unit?

If this is possible, would I have to reposition the hard drive on the
SCSI cable, or just unplug the CD-ROM and run? I might have to sneak
into the SCSI BIOS and disable the CD-ROM in there, huh?

If you have a terminator at the end of the SCSI cable already, just pull out the
CD-ROM. If there is no terminator, you'll have to buy one or replace the SCSI
cable with one that has a terminator installed.

Some devices like CD-ROMs have automatic or configurable internal terminators.
Most or all SCSI HDs do NOT have internal termination.

 

[Overlord]

Whatever device is at the end of the cable must (or at least Should) be
terminated.
Assuming you don't have an active terminator, ie. a little tiny module plugged
into the first open connector after the last device on the cable, then you'll have
to fiddle the termination.

Since the hard drive is so small, I'm assuming it's not LVD. I could be wrong
but you haven't told us what drive you have.
LVD SCSI drives have no onboard termination and require the active terminator
I mentioned above. Smaller, slower, older, non LVD drives, and non HVD drives
can be terminated by jumpers on the hard drive. Download the .pdf file for your
drive and see what jumpers are for termination and make sure it's not an LVD drive,
that is it's interface speed will be LESS than 80meg/sec.

If the CDROM is at the end of the cable, farthest down the cable from the PCI card,
then it is jumpered for termination. Pull the CDROM and jumper the hard drive for
termination and you'll be fine. You don't have to mess with the SCSI BIOS as it
will not see a device other than the hard drive anyway.

If the hard drive is on the end of the cable, with no active terminator after it, then
it is already jumpered for termination. Just pull the SCSI CD from the cable and
4pin molex power connector and you're all set to go.

I'd install the IDE CDROM and set it to boot from it in the motherboard BIOS with
the SCSI drive as the secondary boot device. That way if you want to boot a CD
you just put it in the drive. If you want to boot scsi, just don't have a bootable CD
in the IDE CDROM.

I have a Tyan Tahoe 2 motherboard this is running the floppy disk. The
hard drive (Seagate 2gb) and the CD-ROM are run off a SCSI PCI card.
The CD-ROM is about to crap-out on me and I was wondering if I can
pull it out and then enable one or both of the IDE interfaces in the
BIOS and then hook-up an IDE CD-ROM unit?

If this is possible, would I have to reposition the hard drive on the
SCSI cable, or just unplug the CD-ROM and run? I might have to sneak
into the SCSI BIOS and disable the CD-ROM in there, huh?

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[John R Weiss]

Assuming you don't have an active terminator, ie. a little tiny module plugged
into the first open connector after the last device on the cable, then you'll
have
to fiddle the termination.

In my experience, active terminators are placed at the end of the cable,
regardless of the placement of any other devices on the cable.

 

[Overlord]

...

In my experience, active terminators are placed at the end of the cable,
regardless of the placement of any other devices on the cable.

That's true. It is faster and easier to terminate the end of the cable and have done with it.
In the past occasionally I have terminated the next connector after the last device and had
no problems. Admittedly it may not be strictly electrically sound for the extra cabling.
Generally I fabricate my own cables so I don't have 39 feet of cable coiled up in the case.
Pre fabbed cables I've successfully trimmed to fit on occasion.

I've also run non-LVD devices on non terminated bus segments with no apparent problems
but don't recommend it. I suspect some of the higher end SCSI interface cards don't like that
tho. I recall AHA-2940UW cards didn't seem to care but AHA-2940UW Pro cards take a look
first and will nag mercylessly and balk. For multiple LVD bus segments I've always actively
terminated the last cable connector but still had concerns in borderline electrically noisy
situations that might have called for HVD SCSI devices.

You are right, I should have specified the last cable connector.
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