>50 pin by itself does not mean narrow SCSI. It does, actually, it's the definition of narrow SCSI. narrow is not the same thing as "slow" though.
there are several flavors of SCSI, I'll only go into the older ones 'cuz I remember the most about them. SCSI-1 is five megabytes per second, and is also called "narrow" SCSI. It uses 50 pins. SCSI-2 is ten megabytes per second, and is also called "fast" SCSI. It also uses 50 pins. It's the same as SCSI-1, except that the data clock is twice as fast, so it talks faster. SCSI-2 Wide is twenty megabytes per second, and it's called "Fast and Wide" SCSI. It uses fast SCSI's double data clock, but also transfers data 16 bits per cycle instead of eight, thus goes twice as fast. It uses 68 pins. This is the fastest SCSI you can use in a NuBus Mac. Differential SCSI is a subset of SCSI-2 Wide that uses a different electrical waveform to represent the data, resulting in longer possible cable lengths. Otherwise it's basically the same. You don't see Differential SCSI much anymore. Ultra SCSI is twenty megabytes per second. It uses 50 pins, and has a data clock twice as fast as fast SCSI, four times as fast as slow SCSI UltraWide SCSI is fourty megabytes per second, and is basically Fast and Wide SCSI but with the data clock doubled. It uses 68 pins. Above that you get into different kinds of Low Voltage Differential SCSI, like Ultra160, Ultra320, and their ilk, which I don't know nearly as much about. Low Voltage Differential and Differential are totally different things. 80 pin SCSI isn't really 80 pin SCSI, it's some form of 68 pin SCSI with extra pins added to carry power and jumper settings. The design is so that you can just "plug in" your hard drive in things like RAID cases (and Sun workstations) without worrying about hooking things up or having cables. It's called SCA, which stands for Sun Connector Architechture, after it's inventor, Sun Microsystems. The advantage of all these flavors of SCSI is that a SCSI drive is a SCSI drive. You can plug any kind of SCSI drive into any kind of SCSI card (or motherboard, same thing) that has the same number of pins, and the two will talk the fastest way they both know about. A modern Ultra160 SCSI drive (68 pins) will plug into and give 20 MB/s with a Fast and Wide SCSI SiliconExpress IV NuBus card, for example. Further, you can run 68 pin SCSI flavors as their equivalent 50 pin flavor (or any lower 50 pin flavor, by extension of the above principle) by just terminating off the extra data lines, something that's done with a 68 pin to 50 pin adaptor. Sorry about the long post, but that's the long (and fast and wide) and short of it. -Tyler -- PCI-PowerMacs is sponsored by <http://lowendmac.com/> and... Small Dog Electronics http://www.smalldog.com | Refurbished Drives | -- Sonnet & PowerLogix Upgrades - start at $169 | & CDRWs on Sale! | PowerON Computer Services <http://www.poweron.com> REPLACEMENT PARTS in STOCK Drives, CD-ROMs, RAM, Mac OS SW, Power Supply <mailto:[EMAIL PROTECTED]> Support Low End Mac <http://lowendmac.com/lists/support.html> PCI-PowerMacs list info: <http://lowendmac.com/lists/pci-powermacs.shtml> Send list messages to: <mailto:[EMAIL PROTECTED]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive:<http://www.mail-archive.com/pci-powermacs%40mail.maclaunch.com/> Using a Mac? Free email & more at Applelinks! http://www.applelinks.com
