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#21
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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 Ron Martell wrote:
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. Interesting. Arno |
#22
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Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
Yes, I remember those days before speed of data movement became more
critical for ATA timing aspect to become an issue. Had same experiences, Ron. Fraid we have to be more compliant nowadays. -- Jonny "Ron Martell" wrote in message ... 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." |
#23
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Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
Arno Wagner wrote
wrote Arno Wagner wrote glee wrote glee wrote 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. Nope. An unterminated drive connected to the end actually makes things worse for the device in the middle. Nope. The impedance of that drive is better reflections wise than no drive at all. |
#24
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Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
Arno Wagner wrote
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. Its more complicated than that with most of the lines that arent pure receivers. The ATA ribbon cable has an impedance of 200 Ohm, if I remember correctly. No termination effect at all. Wrong, the drive presents an impedance that is different to no drive 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. Its more complicated than that too if termination is used. But the end-device has no terminator it turns on. It has an impedance anyway. I suspect that at some time that was planned, Not a shred of evidence of that. ATA has always been an unterminated system. but at least the last time I looked at the physical ATA bus characteristics, there was no mention of it anywhere. Because it has always been an unterminated system. That does NOT mean that the drive impedance isnt relevant tho. |
#25
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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 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. And that's what you said. Too stupid even to understand it's own ramblings. Of course there is not physical interaction between multiple IDE busses / channels (of which you incidentially can have more than two or only one). Babble, babble, rant. 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. Nope. Device initialization at power-up or reset only. Not for booting. The Master is supposed to be detected first. Then the slave. Completely irrelevant. After that both are identical, except that they have different select signals. No they don't. And yes, the BIOS is free to assign them any order wanted. Arno |
#26
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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 Ron Martell wrote: 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 than 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. Interesting. In that it shows how you don't have the faintest clue. Arno |
#27
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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 |
#28
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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 Jeff Richards wrote:
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. SCSI is complicated today. U2W cables are actively terminated. Older standards allow terminated devices (i.e. devices with internal termion) as well as external terminators. As it turns out UDMA capable devices has some sort of half-assed device terminaton, i.e. _every_ device on the bus has some pull-up or pull-down resistirs. Quite inelegant IMO. Arno |
#29
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Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
Folkert Rienstra wrote:
AFAIK Which is zip. LOL |
#30
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Can IDE cable's end connector be left idle ( w-o affecting data transfer ) ?
"Jeff Richards" wrote in message
Your comments are confused. And your's are any better? There's no such thing, in SCSI or IDE, as a terminated or unterminated device. Well, there is in the physical sense, as a device that provides the termination. There's a device, a terminator, or no device. The terminator is a cheap way of pretending some sort of device is connected, Uh no. It is pretending that the cable is endless. and it's important for SCSI mainly because of the cable lengths involved. In part. Without any termination a SCSI bus doesn't function at all, nomatter how short. 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, In part. and the IDE interface can cope with it. No, it *can't*. It *could* when interface speeds were still (s)low and the *interface* wasn't yet acting like a *bus*, ie a *transmission line*. Changes were necessary to keep it working with the higher UDMA modes. One of those came to be known as series termination. 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. 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 |
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