GregM Posted March 16, 2006 Report Share Posted March 16, 2006 We are getting ready to purchase a new SCSI card as our system hasn't worked for some time. The only imcompatible device is the old SCSI card. We are looking to purchase an ATTO UL4D for use in a G4 tower. It's the only ATTO card available through local channels. My one question. I read in the Dantz SCSI troubleshootings section that I need to use a WIDE card with a WIDE drive, rather then a narrow card with a WIDE drive. And that intermixing has caused some problems. I believe my drive is considered a WIDE drive, it's a 68 PIN. I noticed the UL4D spechs say it's WIDE and Ultra Wide compatible. However the external connector is a Hi Density 68 Pin connector rather then the standard 68 pin connector. Should this PCI card work and be compatible with other WIDE drives, or will that possibly pose a problem. Greg Link to comment Share on other sites More sharing options...
waltr Posted March 16, 2006 Report Share Posted March 16, 2006 hi greg, what does ATTO say? they are probably the authority in this case. i've found them very helpful in the past. Link to comment Share on other sites More sharing options...
rhwalker Posted March 17, 2006 Report Share Posted March 17, 2006 Quote: I believe my drive is considered a WIDE drive, it's a 68 PIN. I noticed the UL4D spechs say it's WIDE and Ultra Wide compatible. However the external connector is a Hi Density 68 Pin connector rather then the standard 68 pin connector. You will need the right cable and terminator, and you don't say whether your drive is internal or external. If you are connecting to an internal drive in your computer, the UL4D has two HD68 connectors on the top edge of the card, for connecting to ribbon cables with HD68 connectors. The two external connectors on the ATTO UL4D are VHDCI 68 pin (in order to fit two of them on the ExpressPCI card rear panel). It's a bit unclear from your post which "standard 68 pin connector" your drive has, but if it's an external drive, I would guess that it's a HD68 connector. The correct external cables to connect to the UL4D can be found at Cables to Go VHDCI cables. We use their cable #28295 VHDCI to HD68 with Ferrites to connect to the back of our UL4D in our Xserve G5 (with the cable management arm, which is why we need 6 feet of cable). Once you are to the "standard 68 pin connector" size, the usual external interconnect cables such as their cable #28142 HD68 to HD68 with Ferrites can connect any additional SCSI devices. The other, more important thing to note is not to mix LVD (low voltage differential) with HVD, which can blow things up. Choose an appropriate terminator (LVD, etc., preferably active termination) for your setup. There's a nice picture of all the different connectors for the various ATTO cards here ATTO SCSI connectors and also see these nice drawings: ATTO SCSI Connectors. Hope this helps. Russ Link to comment Share on other sites More sharing options...
GregM Posted March 18, 2006 Author Report Share Posted March 18, 2006 Thanks for the info and the reply. To follow up... my drive is external, it uses an HD68 connector. The drive is a Sony AIT drive that is listed as compatible. I think inside the drive itself uses a 50 PIN cable. But the APS case it's in uses an HD68 connector externally. Could that pose and issue? Also, I assume the VHDCI and the HD68 are comaptible then. As I'm trying to make sure we have it hooked up in accordance with EMC's suggetions about using HD68 devices with the correct cards and cables, see bellow. Last question. How do I determine which type of terminator that I need. I.e. LVD or HVD. Also what is active termination, so I know what I'm looking for. And if I was to mount this drive internally do I need to terminate it there as well? Or is the ribbon cable already terminated? Thanks, Greg Montgomery Bellow is EMCs comments that we are trying to follow for 68-Pin device compatibility. 68-pin Wide Storage Device Issue If your storage device has a wide 68-pin interface, make sure it is connected to a wide 68-pin SCSI adapter. Many issues have been found when wide devices have been connected to a narrow 50-pin or 25-pin SCSI adapter when using Mac OS X and therefore this is not a supported configuration. Link to comment Share on other sites More sharing options...
rhwalker Posted March 18, 2006 Report Share Posted March 18, 2006 Quote: my drive is external, it uses an HD68 connector. The drive is a Sony AIT drive that is listed as compatible. I think inside the drive itself uses a 50 PIN cable. But the APS case it's in uses an HD68 connector externally. Could that pose and issue? Probably not, and I would suspect that the drive is using a 68 pin cable if you counted the wires. Specifically, which Sony AIT drive is it? Sony's web site is pretty good with all the specs, and we could poke about to see exactly what the interface is if the specific drive was known. Google is your friend. Quote: Also, I assume the VHDCI and the HD68 are comaptible then. Yep. They are just different connector sizes. That's why I pointed you to the ATTO and Cables-to-Go web pages. We connect to the VHDCI connectors on our ATTO UL4D in our Xserve G5, and the other end of the cable is HD68 to the LVD Exabyte VXA-2 tape drive and autoloader (with a terminator). Works fine, and that's exactly what is common. Quote: How do I determine which type of terminator that I need. I.e. LVD or HVD. Let us hope and pray that you don't need HVD, because if you connect an HVD terminator or device to a SCSI chain with LVD interfaces (like the ATTO UL4D and, I believe, probably your Sony drive), there will be smoke and all of the LVD devices will be trash immediately afterward. HVD was a short-lived technology that tried to permit longer cables with greater noise immunity than standard SCSI by using big (high) voltage differential swings. LVD is the more common and modern standard. But it would be prudent to check your drive's specs at the Sony web site before hooking things up. Quote: Also what is active termination, so I know what I'm looking for. Well, here's a description that is pretty good: SCSI Termination. Explained a little better, the high-speed bus cable has a certain characteristic impedance. If each connector is properly "terminated" with its same characteristic impedance, the electrical signals think the bus goes on forever, and don't reflect back down the bus to interfere with signals traveling behind. Visualize the old trick of a slinky stretched out on a floor, with one end held fast (not "terminated" with the impedance of the slinky). If you wiggle one end of the slinky, when that pulse gets to the far end it reflects off the impedance mismatch, and starts traveling back down the slinky, inverted. The impedance of each conductor of the cable can be modeled as one resistor from each conductor to a negative voltage (the negative LVD swing) and another resistor from that same conductor to a positive voltage (the positive LVD swing). The combined resistance of these two terminator resistors in parallel needs to match the characteristic impedance of the cable in order for signals not to reflect off the end. Additionally, the quiescent voltage seen by the end of the cable is the voltage divider result at the junction of the two resistors in series between the two voltage levels (positive and negative). That's how a "passive" terminator is constructed - two resistors only for each connector, extending to the + and - voltages of the SCSI bus at the terminator. If you think about it, having all those resistors connected between the positive and negative voltages in the terminator causes a lot of current to flow through the two series-connected resistors on EACH signal, for a total of a lot of current being dissipated in the terminator. So, to solve the power problem, "active terminators" have a voltage source ("active element") inside the terminator at the desired quiescent voltage, with a single resistor (of the same resistance as the parallel resistance of the two resistors of a passive terminator) between that voltage source and the end of each conductor (this is the "Thevenin equivalent" of the passive terminator - see Thevenin Equivalent - compare the "voltage divider" (passive terminator, a bit down the page) with the Thevenin equivalent (active terminator, a bit up from the voltage divider example)). Electrically, active terminators and passive terminators appear the same ("Thevenin equivalents") to the signals, but, because most of the time the SCSI bus is undriven or inactive, no current flows through the active terminator's resistors because the bus quiescent voltage matches the terminator's voltage source (both ends of each terminating resistor are at the same voltage, so no current flows). Basic EE freshman course stuff. So, the advantage of an active terminator is that it doesn't load the power supply of the device that supplies power to the end of the SCSI bus. Less heat, less power. Quote: And if I was to mount this drive internally do I need to terminate it there as well? Yep, so the signals don't reflect back onto the SCSI bus. Quote: Or is the ribbon cable already terminated? Nope, but almost every internal SCSI device has a jumper that, when set the right way, will terminate the SCSI bus at the device. For all external devices, that jumper must be set to NOT terminate the SCSI bus, or else you would have termination mismatches every place a device hooked onto the SCSI bus (or two terminators in parallel, if the device was at the end of an again-terminated bus, for 1/2 the desired termination impedance). That's why it would be helpful to know the exact Sony AIT drive, because Sony has good docs on their web site for all their devices, showing jumper positions, interface specs, etc. As for the EMC info: Quote: 8-pin Wide Storage Device Issue If your storage device has a wide 68-pin interface, make sure it is connected to a wide 68-pin SCSI adapter. Many issues have been found when wide devices have been connected to a narrow 50-pin or 25-pin SCSI adapter when using Mac OS X and therefore this is not a supported configuration. All EMC is saying here is not to mix SCSI-1 (narrow 50-pin or 25-pin SCSI) with LVD or Wide SCSI. The SCSI-3 specs are written to be backward compatible, and LVD devices are "supposed" to automatically switch into single-ended SCSI-1 mode (with slower transfer rates) when they detect that they are on a SCSI-1 bus, but you don't want that, and LVD SCSI is much more reliable than single-ended SCSI-1. Hope this helps. There will be a quiz. 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