This guide is for reference only - Accelerate Your Mac!/Mike Breeden cannot be held liable for damages that may occur from attempting any of the procedures shown. Apple computer may void your warranty as a result of user modifications or repairs. I suggest having an authorized Apple Service Center perform this procedure. Although with proper static precautions and exercising care thousands of Mac owners have done this upgrade, we cannot control the actions of others, or be responsible for their equipment. This tutorial is published to document what I did as part of this project.

NOTE: At the time this article was written, Adaptec WIDE SCSI cards are not compatible with G3 CPU upgrade cards other than those from Newer Tech (PowerLogix, XLR8, Bottom Line and MacTell). Newer Tech has a unique hardware fix for the speculative processing issue that prevents Wide SCSI Adaptec cards w/wide scsi drives from mounting the disk at boot. (Noted in early G3 CPU upgrade reviews here and in the FAQ.

Update: In 1999 XLR8, Powerlogix and some other companies updated their G3 CPU card software for a 'virtual firmware' solution to the Adaptec/Wide SCSI drive issue. They also include options to disable speculative access/processing that solves the Retrospect Backup software problems as well. See the 1999 CPU Upgrade reviews for more info.

Most standard MacOS systems come with only narrow SCSI-2 (10MB/sec max rate, 8 bit wide data path) as standard equipment, and the new Apple G3 systems only come with internal narrow SCSI-1 (5MB/sec) as standard equipment. These disk controllers cannot take advantage of today's higher performance Ultra and Ultra Wide SCSI drives, which offer theoretical maximum transfer rates of 20MB/sec and 40MB/sec, respectively. For an excellent introduction to SCSI I highly recommend you read Adaptec's excellent SCSI Primer.

Now that narrow Ultra SCSI (20MB/sec, 8 bits wide), Wide SCSI (20MB/sec, 16 bits wide) and Ultra-Wide SCSI (40MB/sec, 16 bit wide) hard disks are dropping in price (my 2.2Gig Atlas II Ultra/Wide drives cost $229 each) they are rapidly making the older SCSI-2 drives obsolete. If your work involves large Photoshop images, or other disk intensive applications, you should consider a Ultra/Wide SCSI controller and drive as your next performance upgrade. Since all your data starts and ends on the hard disk, disk performance is a key component of any true high performance Macintosh.

As shown below, the on-board SCSI cannot provide the needed speed to take advantage of today's faster SCSI drives, and has no Wide SCSI capability. As you'll see in later installments, in many cases real world applications like Photoshop benefit more from a SCSI upgrade than they do from a faster CPU, due to dependancies on disk I/O speed and efficiency. Simple dedicated task benchmarks like MacBench do not tell the whole story on these upgrades - although the pure disk I/O results shown below provide a glimpse at the kinds of performance increases you can expect.

Documented Photoshop Tests:

In one test that was done by Adaptec, a 2940UW with Ultra/Wide disk was much faster in Photoshop filter tests on a 9500/132 than when the same tests were run on a 9600/200 system using the stock SCSI setup. Far greater performance gains can be had with Raid striping options that these cards support, which show amazing I/O speeds - speeds that are a blessing for high-end Photoshop work with larger files.

Easy Upgrade:

It took all of ten minutes to install the Adaptec card, but about 10 hours to document and photograph all the steps involved, including writing the HTML. I've got extreme detail here, and that's the reason for the length. Based on reader feedback you'd prefer I have too much detail than not enough. If you're intimidated by the length here - don't be. All you're doing is inserting a PCI card, connecting it to your drive(s) and installing a control panel. Like many things, this procedure is harder to describe in detail than to do, but bear with me and you'll know exactly what to expect at each step of the way.

In the PowerTower Pro 180, the 2940UW achieved impressive Read and Write speeds when used with the Seagate Cheetah 4LP drive. Compare the 2940UW/Cheetah results to the stock PowerTower Pro SCSI performance - which included a 2GB 7200rpm IBM AV Rated High-Performance narrow SCSI drive (far faster than the typical SCSI drives in most Apple Mac's, which usually have less than 5MB/sec R/W speeds):

For reference, the Apple 8500 stock 2Gig drive tested at less than 5MB/sec on partition one, and less than 4MB/Sec on the 2nd partition.

Note: Although a few hundred dollars more expensive than a do-it-yourself kit, the Cheetah Bundle from MacCPU is as close to plug and play SCSI as I've seen. See my review and tutorial on installing that kit for more info. In that kit the Cheetah drive comes already formatted, no need to partition, format or jumper/terminate the drive. The kit includes APS's drive sled with cooling fans for use in a 85/9500 or similar Mac.

Adaptec 2940UW Features:

• Up to 40 MByte/sec Ultra Wide SCSI data transfer rate.
  (Raid striped configurations can exceed this figure.)
• SCSI Manager 4.3 compliant
• Connection for up to 15 SCSI peripheral devices.
• PCI busmastering with DMA (Direct Memory Access).
• Tagged command queueing and PCI scatter-gather.
• Support for 255 simultaneous active SCSI commands.
• Automatic active termination.
• Flash ROM for easy updating of the card's Bios.
• Tested for compatibility with hundreds of systems and peripherals from major manufacturers.
• Most popular SCSI host adapter family in the industry.
• 5 Year warranty.

Compatibility Note: it was during writing this tutorial that I discovered that the Adaptec SCSI cards are not compatible with the PowerForce G3 design CPU cards. Both the 2940UW and 3940UW here would not mount a wide HD when the Powerforce CPU card was installed. Although some owners report they do not have the problem, 95%+ of reports from the field indicate it is a problem. Adaptec has acknowledged the issue and there is no workaround or fix planned by either company. The Newer Tech G3 cards were revised (in the card ROM) to fix the problem, but the Powerforce cards have no on-card ROM to allow this patch.

For a comparison of the 2940UW to the ATTO ExpressPCI, HammerStorage JackHammer and Initio Miles SCSI cards with several drivers and even Raid configurations, see the test reports listed on my SCSI Topics page.

Want to know more About SCSI? Raid? Other PCI SCSI cards?

This was the first in a series of SCSI upgrade projects that will walk you through installing and configuring a PCI SCSI controller. Check my SCSI Topics page for tests of all the popular high-performance Mac PCI SCSI controllers and how they compared in several RAID striping tests. That page also has links to tests I've done with 5 of the most popular RAID software packages, tested with each of the 4 PCI SCSI cards under single and dual SCSI card configurations.

Running a dual SCSI card, 4 drive RAID 0 array using low cost Ultra-Wide SCSI drives I've attained sustained I/O rates as high as 58MB/sec! Not bad performance considering I was using low cost Quantum Atlas II 2.2Gig, Ultra-Wide SCSI disks. These disks don't have the performance of the Seagate Cheetah (10,000rpm), but they deliver major bang for the buck. That's the great thing about SCSI over IDE - options for more speed as your needs grow.

As always, if you find this tutorial useful or have questions or comments please contact me. I welcome your comments, suggestions, and experiences with Macintosh hardware.

Use the Feedback form page to let me know what products you'd like to see reviewed, or if you hate forms, just email me.