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#11
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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* |
#12
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Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
"Arno Wagner" wrote:
glee wrote: 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. You are correct that *on a single IDE channel*, the device arrangement can be Master/Slave or Slave/Master or single Master or single Slave. What is not allowed by the IDE controller, though, is Master/Master and Slave/Slave on the same channel. But on different channels, you could have ch.0 Master/ ch. 1 Master and ch. 0 Slave/ ch. 1 Slave and ch. 0 Slave/Master/ch. 1 Master/Slave. The arrangement prohibited is having the same jumpering for both devices on the same IDE channel, i.e. on the same cable. That is imposed by the controller's need to be able to tell the two devices apart which are on the same cable. I think that's what you intended to express, but it wasn't clear. And the implications go farther: A Slave HD can be the "boot drive" just as well as well as a Master HD. All that is required is that the HD be at the head of the HD boot order. The default settings (or settings in BIOSes which don't enable adjustment of the HD boot order) put the Master on ch. 0 at the head of the HD boot order. But this can be changed by readjustment of the HD boot order. Indeed, it's quite legitimate to have the Slave on ch. 1 (the secondary IDE channel) be the "boot drive". *TimDaniels* |
#13
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Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
Timothy Daniels wrote
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? Yep, if that was the system, it would be specified in the standard. |
#14
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Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
Arno Wagner wrote:
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. On more that one occasion, because of the layout of the motherboard and the design of the computer case, I have connected drives using the middle connector for the motherboard with a drive at each end. 40 wire cables with master/slave jumpers set appropriately, of course. But zero problems with using the drives. Ron Martell Duncan B.C. Canada -- Microsoft MVP (1997 - 2006) On-Line Help Computer Service http://onlinehelp.bc.ca "Anyone who thinks that they are too small to make a difference has never been in bed with a mosquito." |
#15
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Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
"Arno Wagner" wrote in message
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 Which is zip. this is more of a historic problem today. Nope, most if not all harddrives still have jumpers for that situation. Arno |
#16
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Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
Stop feeding the swiss troll.
"Timothy Daniels" wrote in message "Arno Wagner" wrote: glee wrote: 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. You are correct that *on a single IDE channel*, the device arrangement can be Master/Slave or Slave/Master or single Master or single Slave. What is not allowed by the IDE controller, though, is Master/Master and Slave/Slave on the same channel. But on different channels, you could have ch.0 Master/ ch. 1 Master and ch. 0 Slave/ ch. 1 Slave and ch. 0 Slave/Master/ch. 1 Master/Slave. The arrangement prohibited is having the same jumpering for both devices on the same IDE channel, i.e. on the same cable. That is imposed by the controller's need to be able to tell the two devices apart which are on the same cable. I think that's what you intended to express, but it wasn't clear. And the implications go farther: A Slave HD can be the "boot drive" just as well as well as a Master HD. All that is required is that the HD be at the head of the HD boot order. The default settings (or settings in BIOSes which don't enable adjustment of the HD boot order) put the Master on ch. 0 at the head of the HD boot order. But this can be changed by readjustment of the HD boot order. Indeed, it's quite legitimate to have the Slave on ch. 1 (the secondary IDE channel) be the "boot drive". *TimDaniels* |
#17
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Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
Multigroup post thwarted. I don't particularly like some of the
participants at one particular newsgroup. ATA basics. Slave in the middle, master on the end. Using cable select or master/slave jumpers, makes no difference. There must be a master for a slave to exist. This is part of the timing aspect for ATA. There's alot of things motherboard makers don't provide information about. Most of use muddle our ways through to learn the hard way. Or, stumble upon a good website to fill that void. Pcguide is a good website. ATA has no terminations per se like scsi. It is however a stub, and reflections are a result. Poor explanation provided, but symptoms are nonetheless accurate. -- Jonny "TE Cheah" wrote in message ... 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 ? |
#18
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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 Oscar wrote:
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. Very relevant. An unterminated drive connected to the end actually makes things worse for the device in the middle. Arno |
#19
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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 Timothy Daniels wrote:
"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? You are entirely correct on how signal termination works. The input inpedance of an ATA device is a CMOS input plus ESD protection. Some mega Ohm or more. The ATA ribbon cable has an impedance of 200 Ohm, if I remember correctly. No termination effect at all. For the device in the middle that is how it should be. Termination in the middle of a signal path is very bad. But the end-device has no terminator it turns on. I suspect that at some time that was planned, but at least the last time I looked at the physical ATA bus characteristics, there was no mention of it anywhere. Arno |
#20
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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 Timothy Daniels wrote:
"Arno Wagner" wrote: glee wrote: 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. You are correct that *on a single IDE channel*, the device arrangement can be Master/Slave or Slave/Master or single Master or single Slave. What is not allowed by the IDE controller, though, is Master/Master and Slave/Slave on the same channel. But on different channels, you could have ch.0 Master/ ch. 1 Master and ch. 0 Slave/ ch. 1 Slave and ch. 0 Slave/Master/ch. 1 Master/Slave. The arrangement prohibited is having the same jumpering for both devices on the same IDE channel, i.e. on the same cable. That is imposed by the controller's need to be able to tell the two devices apart which are on the same cable. I think that's what you intended to express, but it wasn't clear. Sorry. Yes, that was what I wanted to say. Of course there is not physical interaction between multiple IDE busses / channels (of which you incidentially can have more than two or only one). And the implications go farther: A Slave HD can be the "boot drive" just as well as well as a Master HD. All that is required is that the HD be at the head of the HD boot order. The default settings (or settings in BIOSes which don't enable adjustment of the HD boot order) put the Master on ch. 0 at the head of the HD boot order. But this can be changed by readjustment of the HD boot order. Indeed, it's quite legitimate to have the Slave on ch. 1 (the secondary IDE channel) be the "boot drive". Again true. It is a start-up issue for the device detection only. Not for booting. The Master is supposed to be detected first. Then the slave. After that both are identical, except that they have different select signals. And yes, the BIOS is free to assign them any order wanted. Arno |
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