Faster SCSI or Ethernet?

Originally published 13 November 2000 as a Mac Daniel column for Low End Mac.

Q: I have a NuBus Mac, and it seems pretty slow when copying files over my network, which supports 100Base-TX. Should I upgrade to a Fast Ethernet card, upgrade the SCSI card, or both?

A: As much as I love collecting 68K Macs, I really can't see myself spending US$80 for a Fast Ethernet card or $100 for a good SCSI card — like an FWB Jackhammer or ATTO Silicon Express IV. However, that doesn't mean it won't help you. As always, it really depends on your situation. I'll try to explain why you ought to keep your money in your pocket, though.

Any '030-based Mac won't be faster than 3 MB/s on its stock SCSI bus, and only the IIfx will achieve this speed. The IIci clocks in next at 2.1 MB/s, and all the others are only 1.5 MB/s— this is barely faster than 10Base-T Ethernet. Thus, only upgrading the Ethernet card in an '030-based Mac makes very little sense, and the money spent on upgrading both would buy you a reasonably well-furnished PCI Power Mac.

The Quadras can support up to 6 MB/s with high-quality cables; this will probably shift the bottleneck from the SCSI to the Fast Ethernet card, since 100Base-TX Ethernet is limited to around 6-7 MB/s by the Mac OS itself even on a fast Power Mac. (Last time I saw a test, even AppleShare Server running on a 604e-based Power Mac with upgraded SCSI could only deliver about 50 Mbps over 100Base-TX Ethernet, and standard File Sharing is slower still.)

If you're bent on upgrading the Ethernet in a Quadra, go ahead — it might actually make a difference. But don't upgrade the SCSI for the sake of higher Ethernet throughput, since the bottleneck is the Ethernet. Note that the low-profile Quadras (the 610 and 660AV machines) won't take both upgrades — you'll have to choose. You'll also have to buy a NuBus adapter in order to put a NuBus card in the machine if you don't already have one. Forced to choose, I would probably upgrade the Ethernet, since that would give me the option of running the box as a router. Putting a good SCSI card into a box that has room for only one internal hard drive (two without a CD-ROM) is simply wasteful.

A NuBus-based Power Mac will be roughly the same as a Quadra. As with the 610 and 660AV, you don't even have the option of upgrading both on a 6100.

Why would you upgrade the SCSI at all? I can think of a couple of cases. One, you're a collector like myself looking to get an FWB Jackhammer just to have one. Two, you're actually using a G3- or G4-upgraded 8100 (or PPC-upgraded Quadra 950 or 800) as a daily working box, and you're tired of waiting ten minutes every time Photoshop tries to save a 2 MB TIFF file. In this case, putting a faster SCSI card in the box makes a lot of sense, because it will make a noticeable difference in speed whether on or off a network.

The SCSI upgrade by itself won't make your Ethernet run any faster (and indeed is a waste as far as that is concerned). In fact, it's completely worthless without a hard drive that supports faster SCSI speeds. When you consider that adding a Jackhammer or ATTO SE IV card to a NuBus Mac costs about $100, and the hard drive will have to be upgraded to take advantage of that (probably at least another $20 for a used drive, and usually over $100 for a new one), you would really be better off selling the machine you have and putting that money towards a PCI-based Power Mac or a G3 or G4.

copyright ©2000-2004 by Chris Lawson