dca@datacube.UUCP (12/01/87)
We have a new CDC Wren IV, which, other than bad documentation, has been completely satisfactory. It's quiet (relative to the other drives in our howling Sun 3/160), fast (I suspect the biggest bottleneck is the Sun SCSI interface and device driver -- of which I hear a new version is in the works), and cheap (<$2k for us). This is what I used to make the CDC Wren IV (94171-300) 300 Mb SCSI winchester disk drive (5 1/4" full height) work: The OEM manual that came with it was fairly complete on the matter of jumpers and cabling. The only really tricky part about the drive is that the OEM manual does not specify how many cylinders or how many data sectors per track there are. The marketing glossy claims 1365, but I believe this is wrong. I do believe it when it says that there are 9 data surfaces. Since the glossy claims the same bpi density as the wren III (19058), I expect about the same number of sectors per track as it, about 35 (I used 34 for the Wren III, but I'm not sure that's optimal). Using the Sun standalone diag utility, I found there are 586764 user-accessible 512-byte data sectors on the drive (the Wren III reserves 2 cylinders for internal use), which factors into (9 heads)(36 sectors/track)(1811 cylinders). Since 1811 is prime, I concluded there are 1811 cylinders, giving 293 Mb, about right for the drive. So I ended up using this geometry: 1809 cylinders, 2 alternate; 9 heads; 36 sectors/track; interleave 1. If anybody finds a hole in my logic, or confirms this with CDC (they haven't returned my call), please let me know. **************** The rest of this is for our internal use, and for the benefit of people without a manual. The main data cable is a standard SCSI pinout 50-conductor BERG-style mass-terminated connector, with pin 1 on the right-hand side, looking at the back with the PC cards on the underside. See the picture below. There are 4 sets of jumpers on the back. The Factory test jumpers should not be installed for normal operation. Pins 3 thru 5 of the options header select the SCSI unit. It is binary coded, with pin 5 as the LSB. Unit 6 would be configured with jumpers vertically across headers 3 and 4. Mine was set up as SCSI unit 1 (Sun "target" 1, unit 0; "disk sd1 at sc0 drive 8 flags 0"), with a jumper across 5. Pin 1 of the option header is the parity check option for the SCSI bus; remove the jumper to disable parity checking (that's what I did). Pin 2 of the option header controls the motor start option. Installing a jumper prevents the drive from spinning up until it receives a SCSI "Start Unit" command; I left it out. The gndsel header controls the usage of the faston connector to the right of the power connector; installing a jumper on pins 1 connects it to chassis ground; on pins 2 connects it to signal ground. I connected both of them. The term pwr header controls where the power for the terminating resistors comes from. (The terminating resistor packs are the obvious, socketed chips, one in each corner of the data PWA.) If the drive is not the last in a daisy-chain configuration, the r-packs should be removed and no jumpers installed here. otherwise, the packs should be in and one jumper should be installed either vertically next to the SCSI connector (above the t p in my drawing) for internal 5V power, or horizontally across the 2 pins farther away from the PWA for external (SCSI cable) power. Mine is configured for internal power. |-----------------------------------------------------------------------------| | | | | | HDA | | | | | | | | | | | | | | | | | | Factory options gndsel | | test 12345 12 | | ++ +++++ ++ +------+ | | ++ Servo PWA +++++ ++ | power| faston | | ------------------------------------------------------------------------ | | | | | | | | Data PWA | | ------------------------------------------------------------------------ | | r-pack | pin| ++ r-pack | | | SCSI connector 1 | ++ | | +---------------------------------------+ term | | pwr | | | | | | | |-----------------------------------------------------------------------------| David Anderson !mirror!datacube!dca dca@eddie.mit.edu