SCSI Connector

Ian
Macs with inernal SCSI typically have Narrow SCSI-1 8-bit (5MB/s) 50-pin buses, but some also had a second Narrow SCSI-2 bus, for external daisy-chaining, at 10MB/s. 68-pin 20MB/s Wide 16-bit SCSI (internal/external) was achievable with an expansion card (NuBus or PCI).

This comprehensive FAQ page may be of use to you.

Several of the 8 and 9 prefix x100/x500/x600 PPC Macs had the two buses.

Ian,

I'm looking at several older Power Macs to use as servers

I'd really like to know about the x100 series

Are you shopping or physically looking at a stack of machines you already have? If you are shopping, jump to the 8600 or 9600 form factor. Base units can be found for $10 to $25 and many more capabilities, including ease of use.

The 8100 case has more capacity than the 61--s but is a pain to work on. Changing RAM means totally unplugging and removing the motherboard. Drive access is OK if you have small fingers for reaching into tight spaces. The 7100 offered nice design compromises. The AV models came with a card with more video RAM and RCA ports. Those cards can be transferred to a stock x100.

My x100 machines get zero attention now that I have x600 machines.

Jim

The Server [beige] G3 shipped with an Apple/ATTO PCI card [equivalent to the ATTO Express PCI PSC card] a Fast-and-Wide three-drive cable, and Fast-and-Wide drives.

This is interesting because the transfer speed with Fast/Wide drives (40 MB/sec) is comparable to the burst transfer rate of 10,000 RPM drives (50 MB/sec). So the disk transfer-time bottleneck is effectively eliminated, which is exactly what you want for a Server.

The Apple/ATTO UL2D card, which shipped in later G3 and G4 models with Ultra2 [LVD] drives, is even faster. The version Apple shipped just has the second internal 68-pin connector de-populated.

Grant,

You mentioned "The version Apple shipped just has the second internal 68-pin connector de-populated. "

Was there a particular significance to that or just unused.

Jim

Jim-

If you look for them on eBay, the ones that were sold as ATTO cards have the second internal connector in place; the ones that shipped in Macs have the connector position, but the holes are filled with solder. This was done to reduce the cost. It is really tedious to suck the solder out of all those holes and repopulate that connector to get a second internal LVD bus, so no one would ever do it.

I think the history of it was that Apple used the Express PCI PSC in the original Server G3, but wanted it really cheap, so ATTO agreed to make an Apple-branded firmware for it. This meant ATTO would not have to service cards that had Apple firmware, so they could reduce the cost.

Apple later shipped an Adaptec card for their first Ultra2, then used the special ATTO UL2D with Apple firmware and second internal connector de-populated. When I bought my first new G4/400 with build-to-order SCSI, it had the special ATTO card in it.

Those Apple/ATTO UL2D cards are often available at less than US$30, and provide full Ultra2 LVD capability. They can be made to work in the beige G3, but when booted into Mac OS 9 (not Classic), the card conflicts with Foreign File Access in the CD Driver. Since a Server spends all its time in Mac OS X, this is not an issue for me.