As described in Chapter 4, System 7.5 comes with a system extension called SCSI Manager 4.3 (built into System 7.5.3 or later). Get this: SCSI Manager can actually speed up your hard drive by up to 30 percent! It can also expand the number-of-SCSI-devices limit from 8 to 256 per chain — and expand the theoretical number of SCSI chains to 256! (Of course, you’d need a Mac that can handle multiple chains, such as the Quadra 900 and 950.)
Among other tricks, SCSI Manager speeds up Macs by letting them do asynchronous transfers, in which two streams of SCSI information take place simultaneously. So why hasn’t this amazing software made headlines? A 30 percent speed increase — for free?
Because SCSI Manager only works with a very specific combination of hardware and software:
n A SCSI Manager-savvy hard-disk driver. Most people never even think about these invisible drivers; if you’re still using the Mac you’ve had for a couple of years, and you’ve never updated its hard-disk driver, then you won’t get SCSI Manager’s speed boost. The following drive-formatting programs are all SCSI Manager-savvy: HD SC Setup 7.2 or later (Apple), Drive7 (Casa Blanca Works), Hard Disk Toolkit 1.5 or later (FWB), Silverlining 5.6 or later (La Cie), SCSI Director Professional 3.0 or later (Transoft), and
so on.
n A SCSI Manager-savvy Mac model. The Quadra AV and Power Macs have SCSI Manager built into their ROMs (so you don’t need the SCSI Manager extension). SCSI Manager, via the extension, also does its thing on Macs with an ’040 processor (see Chapter 12) — but not on Macs with IDE hard drives, such as the 630 series, nor on ’040 PowerBooks, which use specialized SCSI hardware.
n SCSI Manager-savvy programs. This is the biggest bottleneck of all; almost no programs have been rewritten to take advantage of SCSI Manager’s speed boost. Retrospect 2.1 and later (Dantz) and FileMaker Pro are among the few that have.
As with so many Apple technologies, a terrific bonus awaits us all — but it depends on software companies doing their part.
