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#1
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Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
Per www.pcguide.com/ref/hdd/if/ide/confCable-c.html
"Using the middle connector and leaving the end connector unattached ...... leaves part of the cable "dangling". This is called a stub and creates much worse electrical characteristics on the cable, due to reflections from the unterminated ends of the cable wires. It is not recommended." I 1st ignored this warning, & found my Toshiba cd drive ( using cable select, & assigned by Award bios as 2nd channel's slave device ) though can play any VCD just as well, cannot pass BCM diagnostic ( blue screen of "fatal error" appears in Win98se ) unless I use the end connector of this 80 wire cable to connect this drive ( i.e. bios assigned as master device ) to my ( VIA ) kt266a 's hdd controller. Does any1 here have a similar experience ? If this warning is valid, then why does no mboard / hdd / cdd / dvd / cable manufacturer warn users of this requirement ? |
#2
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Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
In comp.sys.ibm.pc.hardware.storage TE Cheah wrote:
Per www.pcguide.com/ref/hdd/if/ide/confCable-c.html "Using the middle connector and leaving the end connector unattached ..... leaves part of the cable "dangling". This is called a stub and creates much worse electrical characteristics on the cable, due to reflections from the unterminated ends of the cable wires. It is not recommended." I 1st ignored this warning, & found my Toshiba cd drive ( using cable select, & assigned by Award bios as 2nd channel's slave device ) though can play any VCD just as well, cannot pass BCM diagnostic ( blue screen of "fatal error" appears in Win98se ) unless I use the end connector of this 80 wire cable to connect this drive ( i.e. bios assigned as master device ) to my ( VIA ) kt266a 's hdd controller. Does any1 here have a similar experience ? If this warning is valid, then why does no mboard / hdd / cdd / dvd / cable manufacturer warn users of this requirement ? First, IDE cables are not terminated. That means that for the drive on the middle connector it makes no difference whether there is a drive at the end or not! If anybody says different, then they do not understand the subject matter. In SCSI cables (what likley causes the confusion) it is a different matter: The last device on an SCSI bus _is_ terminated and havinf no device there either means the bus is not terminated or it is teminated somewhere in the middle. Both useually cause mor or less secvere problems. Again, the same is _not_ true for IDE cables. The device at the end does _nothing_ for signal quality when the controller and the device in the middle talk to each other. From the point of view of the device in the middle, the end-connector is allways empty. The only exception is during the power-on sequence, but not during normal operation. That said, yes, the electical characteristics are worse, but any well-designed IDE device needs to be able to deal with it. I do have a TEAC CD-writer (CD-W540E) that is sensitive to rounded cables when data is transferred to the device. I get bit-errors on the written CDs. The burner has no problems with normal flat cables, no matter what connector it is on. I would say the device is borderline broken by design. If you use standard length flat cables then the CD drive or IDE controller has likely been damaged, e.g. by static electricity. It usually makes digital I/Os much more sensitive to noise. Arno |
#3
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Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
You are correct as far as what that particular web page refers to: 40-pin,
80-wire IDE cables. It is my understanding however (and the recommendation of the manufacturers), that 40-pin, 80-wire IDE cables *do* require particular devices to be attached to particular connectors on those cables, and that the end connector *not* be left vacant. This is especially true in the example given in the original post: using Cable Select. http://www.pcguide.com/ref/hdd/if/ide/conf_Cable80.htm -- Glen Ventura, MS MVP Shell/User, A+ "Arno Wagner" wrote in message ... In comp.sys.ibm.pc.hardware.storage TE Cheah wrote: Per www.pcguide.com/ref/hdd/if/ide/confCable-c.html "Using the middle connector and leaving the end connector unattached ..... leaves part of the cable "dangling". This is called a stub and creates much worse electrical characteristics on the cable, due to reflections from the unterminated ends of the cable wires. It is not recommended." I 1st ignored this warning, & found my Toshiba cd drive ( using cable select, & assigned by Award bios as 2nd channel's slave device ) though can play any VCD just as well, cannot pass BCM diagnostic ( blue screen of "fatal error" appears in Win98se ) unless I use the end connector of this 80 wire cable to connect this drive ( i.e. bios assigned as master device ) to my ( VIA ) kt266a 's hdd controller. Does any1 here have a similar experience ? If this warning is valid, then why does no mboard / hdd / cdd / dvd / cable manufacturer warn users of this requirement ? First, IDE cables are not terminated. That means that for the drive on the middle connector it makes no difference whether there is a drive at the end or not! If anybody says different, then they do not understand the subject matter. In SCSI cables (what likley causes the confusion) it is a different matter: The last device on an SCSI bus _is_ terminated and havinf no device there either means the bus is not terminated or it is teminated somewhere in the middle. Both useually cause mor or less secvere problems. Again, the same is _not_ true for IDE cables. The device at the end does _nothing_ for signal quality when the controller and the device in the middle talk to each other. From the point of view of the device in the middle, the end-connector is allways empty. The only exception is during the power-on sequence, but not during normal operation. That said, yes, the electical characteristics are worse, but any well-designed IDE device needs to be able to deal with it. I do have a TEAC CD-writer (CD-W540E) that is sensitive to rounded cables when data is transferred to the device. I get bit-errors on the written CDs. The burner has no problems with normal flat cables, no matter what connector it is on. I would say the device is borderline broken by design. If you use standard length flat cables then the CD drive or IDE controller has likely been damaged, e.g. by static electricity. It usually makes digital I/Os much more sensitive to noise. Arno |
#4
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Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
"glee" wrote in message
... You are correct as far as what that particular web page refers to: 40-pin, 80-wire IDE cables. Correction/Typo: That should read: 40-pin, 40-wire IDE cables. Brain failure (again)! I'm not sure I should go so far as to say you are correct there, either..... there can and will be the possibility of "electrical disturbances" regardless. ....glen It is my understanding however (and the recommendation of the manufacturers), that 40-pin, 80-wire IDE cables *do* require particular devices to be attached to particular connectors on those cables, and that the end connector *not* be left vacant. This is especially true in the example given in the original post: using Cable Select. http://www.pcguide.com/ref/hdd/if/ide/conf_Cable80.htm -- Glen Ventura, MS MVP Shell/User, A+ "Arno Wagner" wrote in message ... In comp.sys.ibm.pc.hardware.storage TE Cheah wrote: Per www.pcguide.com/ref/hdd/if/ide/confCable-c.html "Using the middle connector and leaving the end connector unattached ..... leaves part of the cable "dangling". This is called a stub and creates much worse electrical characteristics on the cable, due to reflections from the unterminated ends of the cable wires. It is not recommended." I 1st ignored this warning, & found my Toshiba cd drive ( using cable select, & assigned by Award bios as 2nd channel's slave device ) though can play any VCD just as well, cannot pass BCM diagnostic ( blue screen of "fatal error" appears in Win98se ) unless I use the end connector of this 80 wire cable to connect this drive ( i.e. bios assigned as master device ) to my ( VIA ) kt266a 's hdd controller. Does any1 here have a similar experience ? If this warning is valid, then why does no mboard / hdd / cdd / dvd / cable manufacturer warn users of this requirement ? First, IDE cables are not terminated. That means that for the drive on the middle connector it makes no difference whether there is a drive at the end or not! If anybody says different, then they do not understand the subject matter. In SCSI cables (what likley causes the confusion) it is a different matter: The last device on an SCSI bus _is_ terminated and havinf no device there either means the bus is not terminated or it is teminated somewhere in the middle. Both useually cause mor or less secvere problems. Again, the same is _not_ true for IDE cables. The device at the end does _nothing_ for signal quality when the controller and the device in the middle talk to each other. From the point of view of the device in the middle, the end-connector is allways empty. The only exception is during the power-on sequence, but not during normal operation. That said, yes, the electical characteristics are worse, but any well-designed IDE device needs to be able to deal with it. I do have a TEAC CD-writer (CD-W540E) that is sensitive to rounded cables when data is transferred to the device. I get bit-errors on the written CDs. The burner has no problems with normal flat cables, no matter what connector it is on. I would say the device is borderline broken by design. If you use standard length flat cables then the CD drive or IDE controller has likely been damaged, e.g. by static electricity. It usually makes digital I/Os much more sensitive to noise. Arno |
#5
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Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
In comp.sys.ibm.pc.hardware.storage glee wrote:
"glee" wrote in message ... You are correct as far as what that particular web page refers to: 40-pin, 80-wire IDE cables. Correction/Typo: That should read: 40-pin, 40-wire IDE cables. Brain failure (again)! I'm not sure I should go so far as to say you are correct there, either..... there can and will be the possibility of "electrical disturbances" regardless. True. There will be signal echoes on the wires. The enpoint will indeed get a significantly cleaner signal. But as I said a device at the end will not improve the situation for the device in the middle in any way. It does not matter whether it is an 40/40 or an 40/80 cable. IDE devices just don't do any termination. That means that while inactive the IDE device at the end will just be a very high resistance digital input. No effect on electical echoes on the wires at all. If you have a borderline broken device, then you may observe it only working on the cable end. However if you have a correctly working device it must work in both positions, regardless of whether another device is present. (Disregarding the CS/jumpers issue for the moment.) Arno |
#6
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Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
Arno Wagner wrote:
In comp.sys.ibm.pc.hardware.storage glee wrote: "glee" wrote in message ... You are correct as far as what that particular web page refers to: 40-pin, 80-wire IDE cables. Correction/Typo: That should read: 40-pin, 40-wire IDE cables. Brain failure (again)! I'm not sure I should go so far as to say you are correct there, either..... there can and will be the possibility of "electrical disturbances" regardless. True. There will be signal echoes on the wires. The enpoint will indeed get a significantly cleaner signal. But as I said a device at the end will not improve the situation for the device in the middle in any way. Wrong, it reduces the 'signal echoes' which are actually the sharp edges getting reflected off the impedance discontinuity. Thats reduced with a drive on the end. It does not matter whether it is an 40/40 or an 40/80 cable. IDE devices just don't do any termination. Irrelevant. The drive has a different impedance to no drive. That means that while inactive the IDE device at the end will just be a very high resistance digital input. Wrong again. No effect on electical echoes on the wires at all. Wrong again. Its significantly different impedance to no drive. If you have a borderline broken device, then you may observe it only working on the cable end. However if you have a correctly working device it must work in both positions, regardless of whether another device is present. (Disregarding the CS/jumpers issue for the moment.) Separate issue entirely. |
#7
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Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
"Arno Wagner" wrote:
IDE devices just don't do any termination. That means that while inactive the IDE device at the end will just be a very high resistance digital input. No effect on electical echoes on the wires at all. If the input impedance of the device matches that of the cable, there will be no reflection. That is why high-freq comm receiver designers try to match the input impedance to the cable impedance. Are you saying that the input impedance of ATA devices do not match the impedance of IDE ribbon cable? *TimDaniels* |
#8
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Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
Your comments are confused. There's no such thing, in SCSI or IDE, as a
terminated or unterminated device. There's a device, a terminator, or no device. The terminator is a cheap way of pretending some sort of device is connected, and it's important for SCSI mainly because of the cable lengths involved. It doesn't really matter for IDE because the impact of an unterminated connector on the signal quality (ringing, overshoot) is much less with the shorter lengths involved, and the IDE interface can cope with it. But there is still a difference in signal quality between an IDE cable with a device connected and one without. An 'Inactive' IDE device is not particularly high resistance, and certainly has an impact on signal quality compared with an open connector. -- Jeff Richards MS MVP (Windows - Shell/User) "Arno Wagner" wrote in message ... In comp.sys.ibm.pc.hardware.storage glee wrote: But as I said a device at the end will not improve the situation for the device in the middle in any way. It does not matter whether it is an 40/40 or an 40/80 cable. IDE devices just don't do any termination. That means that while inactive the IDE device at the end will just be a very high resistance digital input. No effect on electical echoes on the wires at all. If you have a borderline broken device, then you may observe it only working on the cable end. However if you have a correctly working device it must work in both positions, regardless of whether another device is present. (Disregarding the CS/jumpers issue for the moment.) Arno |
#9
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Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
In comp.sys.ibm.pc.hardware.storage glee wrote:
You are correct as far as what that particular web page refers to: 40-pin, 80-wire IDE cables. Same for 40 pin 40 wire cables. It is my understanding however (and the recommendation of the manufacturers), that 40-pin, 80-wire IDE cables *do* require particular devices to be attached to particular connectors on those cables, and that the end connector *not* be left vacant. This is especially true in the example given in the original post: using Cable Select. In fact cable select is the only reason for this. There is no other one. If you jumper the devices to slave/master you can have them in arbitrary order, number and position on these cables. With cable select the device at the end is the master (during boot-up) and the device in the middle the slave. Some devices will fail to start or have problems if they are used as slave and no master is present. AFAIK this is more of a historic problem today. Arno |
#10
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Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
Arno Wagner wrote:
In comp.sys.ibm.pc.hardware.storage glee wrote: You are correct as far as what that particular web page refers to: 40-pin, 80-wire IDE cables. Same for 40 pin 40 wire cables. It is my understanding however (and the recommendation of the manufacturers), that 40-pin, 80-wire IDE cables *do* require particular devices to be attached to particular connectors on those cables, and that the end connector *not* be left vacant. This is especially true in the example given in the original post: using Cable Select. In fact cable select is the only reason for this. There is no other one. If you jumper the devices to slave/master you can have them in arbitrary order, number and position on these cables. Pity about what the ata standard recommends. With cable select the device at the end is the master (during boot-up) and the device in the middle the slave. Some devices will fail to start or have problems if they are used as slave and no master is present. AFAIK this is more of a historic problem today. |
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