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What is USB?
USB (Universal Serial Bus) is a standard connection type that allows you to plug in devices such as keyboards, scanners, and digital cameras into your iMac. USB is a totally different port type than SCSI ports and traditional serial ports, and has several advantages. For example, USB devices are hot-pluggable. In other words, you can plug in devices when your computer is turned on, and you can safely use them without having to restart. Furthermore, up to 127 USB devices can be hooked together. USB is emerging as an industry standard in the computer world, and will prove extremely useful on the iMac.
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How fast is USB?
USB operates on two channels, a high speed channel and a low speed channel. The high speed channel has a transfer rate of 12 megabits per second. The low speed channel operates at 1.5 megabits per second. Notice that the notation used is megabits per second. This is different from megabytes per second. When translated into megabytes per second, the high speed channel runs at 1.5 megabytes per second, and the low speed channel runs at 0.1875 megabytes per second. Notice that the high speed channel is exactly 8 times the speed of the low speed channel. Typical low speed devices are keyboards, mice, and joysticks. Typical high speed devices are scanners, printers, modems, and hard drives.
However, it is important to note that neither channel will reach the optimal transfer rate listed. One reason for this is that USB has to transfer essential information along with the info that the individual devices are transferring, which takes up some of the bandwidth. There are other reasons, but they are beyond the scope of this question. For more information on USB bandwidth, see http://developer.intel.com/design/usb/papers/bwpaper2.htm and http://www.usb.org.
We should also note that USB is several times faster than ADB (traditional serial) ports and serial ports. Therefore, serial devices that are ported to USB may see great speed increases. However, USB is much slower than SCSI devices, and is downright snail-like when compared to Firewire. Hard drives, removable drives, CD-ROM drives, and other SCSI devices, when ported to USB, will run much slower than their SCSI counterparts. In fact, USB is just not fast enough for some bandwidth hogs, like CD-Rewritable drives.
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Will I notice a performance decrease if I chain several devices together?
Most users will not see any type of performance decrease, because it takes several devices working at once to achieve the maximum transfer rate of USB. For example, if a user were to connect a keyboard, a mouse, a scanner, a printer, and a joystick, performance probably won't decrease noticeably. For one, the keyboard, mouse, and joystick are all low speed devices. Second, it is not likely that all of those devices will be in use simultaneously. In order to slow the chain down, one would need to add at least one high-speed device (like a hard drive) that is constantly active. Note that performance decreases will vary from user to user. It is difficult, even with hard figures, to predict what list of devices will induce a performance decrease, because different users will use different devices differently (we’re all "thinking different," right?).
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What's the deal with USB cables?
USB high speed channels and low speed channels run over different kinds of cables. High speed cables use a twisted pair configuration, and have special shielding. Low speed cables aren't twisted, and don't require the special shielding. It is dangerous to interchange the use of cables between high speed and low speed devices for several technical reasons.
USB cable lengths are also limited. The current maximum for low speed cables is three (3) meters. The maximum length for high speed cables is five (5) meters. Over longer distances than these limits, USB power distribution can be disrupted, and USB signals may be distorted. For these reasons, it is highly recommended that cable extenders not be used to extend the length of USB cables.
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My iMac only has two USB ports, so how can I connect more than two devices?
One of the key features of USB is that it can support up to 127 devices chained together. This is accomplished using hubs. A hub is a device that turns one USB port into multiple USB ports. Hubs are classified by being either bus-powered or self-powered. Bus-powered hubs are powered by the bus (the
chain of devices); no external power supply is needed. Each port on a bus-powered hub can draw up to, but no more than, 100 mA (milliamps). Bus-powered hubs cannot supply more than four USB ports, due to the electrical limitations of the bus. Self-powered hubs are powered by an external power supply such as an AC adaptor. Each port on a self-powered hub has to draw at least 500 mA for an active device, but cannot supply more than 5 A (amps). There is no limit to the number of ports that a self-powered hub can supply, as long as it can supply the required power to each port. However, according to the USB 1.0 Specification, a reasonable limit is seven ports.
Hubs can also be built into devices. The keyboard that is included with the iMac serves as a hub. The keyboard plugs into the iMac, and the mouse plugs into a port provided by the keyboard, leaving one USB port free on the iMac itself, and one free port on the keyboard (as it is a two-port hub, and one of the ports is taken up by the mouse).
The ports on your iMac are referred to as the root hub. Beyond the root hub, a total of five levels of hubs are allowed. In other words, you can have five hubs chained together in series, with the first hub making a connection with the root hub. This "limitation" will be unimportant to most users, since most of us will never use more than a few peripherals on each USB-enabled computer.
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What's the deal with the iMac’s modem? Is it 33.6 or 56k?
The iMac has a 56k modem, which supports both the V.90 standard protocol, and the K56flex proprietary protocol. This decision was announced on July 8, 1998, in response to overwhelming customer demand for the faster modem (the iMac was initially designed with only a 33.6 modem).
Special thanks to: Kristoffer Peterhänsel
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I have an older Mac, with a lot of data on the hard disk. If I get an iMac, how am I going to get my data onto it, with no floppy and no SCSI?
Good question. We have several possible solutions to this problem, but first we would like to talk about transferring data. In most cases, there's really not that much data on the old machine that needs to be transferred. Generally, users will want to save their documents, which are (usually) pretty small. It's a bad idea to try to transfer applications -- it would be a much better solution just to reinstall them from the original CD's on the iMac. So this may not be as big a deal as it sounds. Users who have a massive amount of data should invest in a networking solution. Most of us, however, can get away with using the Internet. Here are our scenarios and solutions:
IrDA is Available: the old machine is a PowerBook or desktop with an infra-red (IrDA) port.
Solution: network the old machine to the iMac using AppleTalk over the infra-red ports. Keep the machines within three (3) meters of each other, and transfer the files at your leisure, in either direction.
Ethernet is available: the old machine does not have IrDA, but does have a 10 or 100BaseT ethernet adapter.
Solution: using the built-in 10/100BaseTX ethernet interface on the iMac, connect the two machines via ethernet. If an ethernet hub is available, simply plug the iMac into the existing hub. A simpler (and cheaper) option, if a hub is not already present, is to use a "crossover" cable to connect the two machines directly, thus obviating the need for a hub. Note that standard ethernet cables will not work -- several pins must be crossed on one end of the cable.
Modem is available: the old machine does not have IrDA or ethernet, but it does have a modem.
Solution: Upload the files to an ISP (or email them to yourself), then log on with the iMac and receive them. If two phone lines are available, the machines can connect directly with each other, using ZTerm or ARA (if available). Theoretically, the machines can also be connected directly via a telephone cable, although getting the modems to connect may be a bit funky.
Worst-case scenario: the old machine has none of the listed technologies. However, since it’s a Mac, it has built-in Localtalk (every Mac has this).
Solution: Purchase a Localtalk-to-ethernet adapter and a crossover cable, then connect the machines together on this simple ethernet network. Localtalk-to-ethernet adapters are listed on our peripherals page.
Special thanks to: Ben Kimball and Kristoffer Peterhänsel
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I need to transfer data between several distant locations on a regular basis, and I’ve been using floppies for this. How can I continue to transfer this data with an iMac?
You have two major options:
Buy a floppy drive (or SuperDrive) then use standard floppies to transfer data, or
Use networking to transfer the files. You can upload the files from each location to a central computer (using FTP or email), then download them from each remote computer as needed.
Another possibility is iMacFloppy, an online solution which allows file uploading and downloading via a Web browser -- for free!
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Is the iMac upgradeable?
Yes. Apple has established the public stance that none of their machines are "upgradeable," due to some legal trouble over that specific term. In reality, the iMac is highly upradeable. It will support more than 128MB of SDRAM, and can be upgraded to 6MB of VRAM. Also, the CPU is on a removable card, so it will theoretically be upgradeable via third-party replacements. CPU upgrades may be cost-prohibitive, though -- it may be cheaper just to buy a new iMac, rather than upgrade the processor. It is remotely possible that the hard disk and CD-ROM may be upgradeable, but it would require a lot of work to get inside the machine to access those components, so don't bet on it.
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Will I be able to use my old ADB devices, like my StyleWriter, or my Wacom graphics tablet?
Yes. A serial-to-USB adapter called the iPort, made by Griffin, allows iMac owners to use legacy peripherals. Check out Griffin's iPort page for more!
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What scanners will work with the iMac? I know I need a USB scanner, but are any out yet?
UMAX has announced its USB-based Astra 1220U scanner, which will be out about the same time as the iMac, for $179. Other options may also be available. For example, although they have not yet announced the product, Microtek is rumored to be developing USB scanners and should soon announce a time frame for Mac versions. Visit our Peripherals section for the latest details.
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What kind of RAM does the iMac use?
The iMac uses SDRAM SODIMMs. See our iMac RAM section for a very thorough explanation of the iMac's RAM configuration.
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What is screen resolution?
Computer monitors display images in the form of pixels. This is similar to a mosaic of many tiles. The tiles are colored and displayed in a fashion that creates a pattern. A monitor works the same way, except the tiles are called pixels, and they aren't "set in stone" -- pixels change color in order to make new images. Each monitor can display a certain number of pixels horizontally and a certain number of pixels vertically. The iMac's monitor can display three different resolutions: 640 pixels across by 480 pixels down (written 640x480), 800x600 pixels, and 1024x768 pixels. If you experiment with monitor resolutions on your iMac, you'll learn that using the highest resolution (1024x768) will make things look incredibly small (although you can fit more stuff on the screen). The most commonly used resolution is 800x600, although many people still use 640x480, since it looks nice and large on the screen.
You can change the resolution of the screen by going to the Monitors and Sound Control Panel. That is found by either choosing "Control Panels" from the Apple menu, or by choosing the Control Panels folder under the System Folder in the hard drive window in the Finder. Click on the Monitors button at the top of the Monitors and Sound Control Panel, and change your resolution from there. (Note: you can also change resolutions from the Control Strip, which is that little tab thingie on the bottom-left of the desktop. Click on the tab to expand the Control Strip, and explore!)
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What is an "ethernet crossover cable?"
An ethernet crossover cable is a special kind of cable that is used when you only want to connect two ethernet devices together, such as the iMac and an older Macintosh with an ethernet port. The crossover cable is for a direct connection between only two devices, so it can't be used on an ethernet network with more that two devices, or where hubs are employed.
A simple application of the crossover cable, as stated above, is to connect an older ethernet-capable Macintosh to the iMac. Simply plug the crossover cable into the ethernet ports on both machines, and turn AppleTalk on under the AppleTalk Control Panel in the Control Panels folder. Make sure "Ethernet" is selected (usually AppleTalk defaults to using the Printer port, so you want to force it to look on the Ethernet port). Then you can go to the Chooser under the Apple Menu, click on Appleshare, and select the hard drive of the other computer. Then file transfer is a cinch! Note that you will have to "log in" to the other computer via AppleShare -- the user name and password for each computer is stored in the Users and Groups Control Panel.
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What is HFS+?
HFS+ is the way that the iMac stores data on the hard drive. This is a newer method than HFS (hence the plus sign). A computer stores bits of data into little "boxes" called allocation blocks. Using the old HFS system, no matter how big the hard drive is, it still has a fixed number of allocation blocks. If the hard drive can hold 40 megabytes of data, the number of allocation blocks is the same as a hard drive holding 4 gigabytes. The allocation blocks have a predetermined size based on the size of the hard drive. In effect, on larger hard drives the allocation blocks will be larger. That is why if you save a text document with only a few characters in it, the file may be listed as taking up several kilobytes, whereas the file itself only contains a few bytes. HFS+ allows the computer to have many times the number of allocation blocks that HFS can handle, thus file sizes are smaller and more data can be stored on the hard drive.
If you are curious, when working with older Macs with the HFS system, click on a file and choose "Get Info" from the File menu in the Finder. It will say something like "20K on disk (12,132 bytes used)." As you can see, the allocation block is 20K, but the file only takes up a portion of the allocation block. With HFS+, the allocation blocks are much, much smaller, so more data can be stored on the hard drive.
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What does the i in iMac mean?
Good question! The "i" could mean a lot of things -- innovative, interesting, even idiotic (if you're a PC user :). But officially, the "i" is for "Internet." Apple is promoting iMac as having "The excitement of the Internet, with the simplicity of a Macintosh." (Variations of this phrase also abound) Check out Apple's iMac page for some very slick advertisements, and more on our favorite "Bondi blue gumdrop."
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What's "Bondi blue?"
According to Apple's designers, Bondi (pronounced bond-EYE) blue is the color of the surf at Bondi Beach in Australia. The iMac features a color scheme which Apple describes as "Bondi blue and ice" -- the "ice" is better known to consumers as "white."
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What's the best deal I can get on [insert peripheral name here] for my new iMac?
We don't directly provide availability and pricing information for iMac peripherals, although many of them do show up in the news. For these sorts of questions, we recommend the excellent deal-iMac, which features all sorts of cool iMac and iMac-related deals.
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My iMac is broken. Will you fix it?
Sorry, nope. Owners of iMacs with warranty issues will need to contact the retailer first, and Apple as a last resort. iMac iNfo provides end-user service for iMac owners, but unfortunately, we don't do hardware repairs. :)
Now, that said, if you live in Tallahassee, Florida, our parent company would be glad to fix your broken Mac stuff. Check out The Macguys, an Apple-authorized VAR and Service Center.
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I want to buy an iMac from someplace online -- who should I buy from, and how can I send a kickback to iMac iNfo, my favorite site?
Wow, this is the kind of question we like to hear. :) Seriously, folks, there are a lot of retailers on the Web who have great deals on iMacs. Some of our favorites are ComputerTown, MacMall, and Small Dog.
Of course, we'd love to make a few bucks from your iMac purchase. We endorse Cyberian Outpost, and encourage you to buy an iMac (or other expensive stuff :) via this link.
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I'm new to Macs, and am a little confused. What's a good beginning Mac book?
We like "Mac OS 8 for Dummies" by Bob Levitus. This book helps users get acquainted with the various cool features in the Mac OS -- and it's a quick, easy read.
To buy this book online, follow this link to check it out at Amazon.com.
Other Mac books, and general Internet/computing books, can be found at the The Macguys Bookstore.
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