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TidBITS#339/05-Aug-96
Do you think the Internet is too slow? What if there were a simple thing we could all do to make it faster? Long-time technology writer Cary Lu weighs in with a simple suggestion. Also, learn about hot new Macs from Power Computing, DayStar, UMAX, and Apple; find guides to everything at this week's Macworld Expo in Boston; and increase your Mac knowledge as Chad Magendanz sets down the definitive word on disk images.
Topics:
Copyright 1996 TidBITS Electronic Publishing. All rights reserved.
Information: <info@tidbits.com> Comments: <editors@tidbits.com>
This issue of TidBITS sponsored in part by:
As you may have noticed last Friday, we sent out the first test message to almost the entire TidBITS mailing list. It was quite successful, as was the release of DealBITS that day as well, which was the first stress-testing of ListSTAR/SMTP. We're not quite sure whether we'll distribute the first complete issue via ListSTAR next week or the week after, but it will be soon. In the meantime, if you are not on the TidBITS list and wish to subscribe (all existing subscriptions will be transferred), send email to <tidbits-on@tidbits.com> rather than working through the Rice LISTSERV. [ACE]
Apple Announces New Macs -- As anticipated in TidBITS-337, Apple has announced faster versions of the Power Mac 7600, 8500, and 9500, along with a new top-of-the-line 9500/180MP that features two PowerPC 604e processors running at 180 MHz. The new 9500 and 8500 models are based on the PowerPC 604e, whereas the revamped 7600 sports a 132 MHz PowerPC 604 processor. All the new machines feature 8x CD-ROM drives and upgradable CPU daughter cards that should support speeds of up to 250 MHz. Prices range from about $3,000 for the Power Mac 7600/132 to $5,700 for the Power Mac 9500/180 MP. Also of interest to owners of recent Power Macs, Apple announced a 180 MHz PowerPC 604e-based CPU upgrade card for about $900. Availability of these systems varies; a few should appear in late August, others should arrive in September.
Additionally, Apple officially announced the Performa 6400-series, sporting a mini-tower design and PowerPC 603e CPUs running at 180 and 200 MHz, priced from about $2,400 to $3,000. I've heard reports that some dealers currently have these Performas in stock. Apple also announced Avid Cinema, a PCI-based digital video editing system available for $459 as an option for 6400 Performas. [GD]
<http://product.info.apple.com/pr/press.releases/1996/q4/960802.pr.rel.pm604e.html>
<http://product.info.apple.com/pr/press.releases/1996/q4/960802.pr.rel.perf6400.html>
Clone Wars Heat Up -- Lest you think Apple is alone in showing off new machines this week, hold on to your socks: Power Computing, DayStar, and UMAX are competing for your attention too. In addition to its recently-introduced PowerTower Pro (see TidBITS-337), Power Computing has announced a PowerBase line of consumer-oriented Mac-compatibles starting at about $1,500. Built around the PowerPC 603e, PowerBase systems range in speed from 180 to 240 MHz, sport three PCI slots, 8x CD-ROM drives, and (gamers take note!) video acceleration that improves 3-D texture mapping and QuickTime performance.
What's more, DayStar is introducing the new Genesis MP 360+ (with two 180 MHz 604e CPUs, starting at $5,500), in addition to 180 and 200 MHz versions of its four-processor offerings, starting at $8,500 and $10,000. These systems are targeted at high-end graphics and video professionals, and DayStar is reportedly shipping them with no hard disks or RAM to let customers more easily customize the systems.
Rounding out the pack, UMAX is expected to show a new spate of SuperMac-branded Mac-compatibles at Macworld, including revved-up versions of its S900L series and a set of 603e-based "SuperMac C" consumer machines due in September. The SuperMac C series reportedly range in speed from 140 to 200 MHz, sport 8x CD-ROM drives, and range in price from $1,600 to $2,600. As of this writing, DayStar's and UMAX's Web sites don't cover their new products, but they'll probably make information available soon. [GD]
<http://www.powercc.com/Product/CPUs/pbase.html>
<http://www.daystar.com/>
<http://www.supermac.com/>
BulkRate to Speak TCP/IP -- Greg Neagle is readying version 2.5 of the shareware BulkRate, an offline message reader for FirstClass servers. BulkRate lets FirstClass users retrieve mail and conference messages for reading offline; version 2.5 supports TCP/IP connections to a FirstClass server, is compatible with FirstClass's threading features, and can use any available serial port for modem connections. Though SoftArc, publishers of FirstClass, have been working on an offline client for years, Neagle's BulkRate is the only viable solution available now. A beta version of BulkRate 2.5 is available via FTP or from the system fc.digitalpopcorn.com (port 3000, username and password "br", sans quotes) using the FirstClass client. [MHA]
<ftp://users.aol.com/gregneagle/pub/>
by Tonya Engst <tonya@tidbits.com>
TidBITS-338 had a MailBIT pointing Macworld Expo attendees to a Newton-based Boston subway map and noting that Adam will be doing a book signing at the Macmillan booth on Thursday from 11 to 1. Last week, I didn't know what booth Macmillan would be in, but with the help of a Director-based program called booth.finder from Macworld Online, it appears that the Macmillan will be exhibiting at the World Trade Center, booth 5604.
Booth.finder enables you to figure out exactly where different vendors are located and become better oriented to the layout of the two exhibition halls. You can run the application live over the Web if you have the appropriate Shockwave plug-in installed, though I recommend downloading a stand-alone version (available for Mac or Windows), which you can run anytime you like without being connected to the Internet. Over my 56K frame relay connection, it took almost a minute for the plug-in to load.
<http://www.macworld.com/expo/boston.expo.96.html>
Those who are less interested in finding specific booths than in finding specific parties won't want to miss the Hess Macworld Memorial Party List. This list was formerly maintained by Robert Hess, the MacWEEK associate editor who died earlier this year (see TidBITS-310). You can view the list on the Web or request it by sending email to <partylist@aol.com>.
<http://www.xensei.com/users/ileneh/HessMemList.html>
If you can't attend the show but have a sufficiently net-savvy Macintosh, you can take advantage of Apple's reporting about the show. Apple will be presenting a number of events, including webcasts of keynote speeches, a spycam, and live chats featuring Expo "movers and shakers."
<http://live.apple.com/macworld/>
A few other organizations and individuals will no doubt be providing daily coverage of the show; a quick search in your favorite search engine on "macworld expo boston" should find those reports as they go online.
by Cary Lu <carylu@aol.com>
Will the Internet ever get faster? Can the Internet backbone capacity ever catch up with the increase in demand, let alone get ahead? Each new Internet development - streaming audio, Internet telephony, video conferencing - increases the traffic. Even users with ISDN or T1 connections to the Internet have to wait for many Web pages, because the fast connection only helps with the final mile, the connection from your Internet provider to you.
Some Internet services may start caching specific Web sites ahead of time, so subscribers can get fast access from a local server. That fast access may cost extra and how the money might be divided between the Web site owner and the cache owner remains to be seen (not to mention the copyright issues when copying a Web site). But, such caching increases the overall traffic because entire sites must usually be transferred to the cache, rather than simply the pages that the subscribers want to look at; there's no way to predict which pages will be of interest.
All these developments have led to predictions of severe traffic jams, even of Internet meltdowns.
I have a modest proposal. Within our present Web servers and browsers, we already have the tools to overcome the traffic jam. I propose that one day a month - say from midnight on the first Sunday of each month to midnight Monday, Greenwich Mean Time - everybody using the Web should agree to turn off graphics and limit their serving and browsing to text-only. Real-time audio, Internet telephone conversations, video conferencing, and other bandwidth hogs can wait for a day. With only text traffic, the speed of the Internet should increase spectacularly.
Of course graphics serve an important function, so graphics that the user specifically asks for will be served. What will be banned are the gratuitous graphics that the user does not specifically request. Why does any Web page have a background pattern, anyway? The backgrounds simply clog up the works without adding any information. No one would put up with a book that had intrusive patterns on the page. Many Web page have large, useless graphics that serve no function except to take up time. How many times have you waited out the endless download of some stylized logo for a company whose name you already know? After all, you selected their Web page.
With my proposal, for at least for one day a month we can get some work done on the Internet. For the rest of the month, it's molasses as usual.
Some simpler steps might be taken by browsing software. Browsers should have settings so that they automatically won't download graphics over an adjustable size. HTML tags should separate essential from optional graphics, although this would require some discipline on the part of Web page designers, the very group responsible for many of the interminable waits.
Some people will argue that my proposal is impossible; Internet users as a group will never agree to text-only Mondays. Maybe. But think about this the next time you need to find some information on the Web.
by Chad Magendanz <chad@halcyon.com>
[With Apple's recent flood of software releases and updates, TidBITS has been receiving a number of questions about disk images: what they are, how to use them, and where they came from. Since few people know more about disk images than Chad Magendanz (author of the widely-acclaimed disk image utility ShrinkWrap), when Chad volunteered to write an article on the subject, we took the opportunity to chain him to his keyboard, crack our whips, and get a definitive run-down on disk images and disk image software. Enjoy! -Geoff]
At the most basic level, a disk image is simply a file that contains a verbatim copy of every sector from a disk. Although disk images of floppy disks are by far the most common, the concept applies to disks of any size. As the cost of high-capacity storage has decreased, people have been using disk images for more than distributing system updates. Mac users are finding it increasingly difficult to justify hanging on to the hundreds of floppies when they can preserve images of these floppies neatly on high-capacity, removable media. After all, when one CD-R disk can easily hold over a thousand compressed floppy disk images, it suddenly becomes realistic to carry your complete software archive wherever you go.
Exposing An Image -- Disk images ensure that everyone receives the same material electronically that they would receive if they were handed a floppy disk. You can think of a disk image as a temporary scratch file that allows for time-delayed disk duplication: you simply run a disk image utility to recreate the original disk. To ensure that the disk reproduces correctly, disk images contain checksum values. Checksum values are virtually unique "signatures" generated from a disk's content; since the odds of two disks having different data and the same checksum value are astonishingly low, checksums are an efficient way of making sure disks are identical.
When copying a floppy disk, it doesn't always work well to drag the disk's contents to a different disk or to a folder. A disk duplicate made from an image file is an exact duplicate, whereas a disk copy made by dragging icons is not. Disks created from image files duplicate their originals exactly, including icon placement, window appearance, and the disk name. Disk images offer the added assurance that all files have duplicated correctly and completely. More importantly, many installers fail to recognize disks copied by dragging icons, even if these disks appear identical to their originals.
The Virtual Volume -- Originally, an obvious drawback to image files was that you had to copy an image file back to a real floppy disk to use it, an annoying and time-intensive process. Fortunately, there are now several reliable utilities that enable Mac users to mount disk images on the desktop as virtual floppy disks. These utilities allow the system to think that an actual floppy disk has been inserted, and some even allow you to mount images as unlocked volumes so you can make and save changes to the image files.
In addition to allowing you to conduct a complete installation without touching a floppy disk, mounted disk images offer several less obvious but equally important applications. Think about it: Macs without high-density SuperDrives (or PowerBooks with no floppy drive at all!) can access any type of floppy if you can make a disk image and transfer it via a network connection. You can even use mounted disk images as temporary partitions like a RAM disk, but unlike most RAM disks, volumes created from mounted images can be created or destroyed at any time without restarting your machine. Finally, the checksums generated for disk images can be used to track changes made to media released for software development, manufacturing, and distribution.
Disk Image Utilities -- The original disk image utility for the Macintosh was Apple's DiskCopy, written by Steve Christensen at least seven years ago. As the years went by and Apple's original offering saw no significant updates, many new disk image utilities (and new disk image file formats) began to appear. Here's a chronological summary of utilities currently available:
<ftp://ftp.support.apple.com/pub/apple_sw_updates/US/mac/utils/Disk_Copy_4.2.hqx>
DART 1.5.3 by Ken McLeod from Apple. This utility went a step beyond DiskCopy 4.2, adding interface improvements, simple drag & drop functionality, and a new image file format that supported RLE and LZH compression. Unfortunately, DART suffers from slow performance compared to DiskCopy.
<ftp://ftp.support.apple.com/pub/apple_sw_updates/US/mac/utils/DART_1.5.3.hqx>
DiskCopy 5.0d1-6.0 by Steve Christensen (and "anonymous contributors"). Based on a beta of DiskCopy 5.0 that was leaked to the general public without Steve's consent, this application has been lurking on BBS's for years, wearing several different version numbers. Although they look and act much like DiskCopy 4.2, these builds add support for two new image file formats, an RLE compressed disk image and a self-extracting disk image that can decompress and save itself to floppy disk. Use of these versions of DiskCopy is discouraged since they're not supported by Apple and the new image file formats they produce don't work with other disk image programs.
MountImage 1.2b2 by Steve Christensen. This control panel can mount up to eight disk images on the desktop. Unfortunately, MountImage has a serious bug that can cause data corruption if the original image file is split into more than three fragments when stored on disk. In this case, MountImage can lose track of some data fragments, blindly reading and writing to blocks that may not belong to the image file, which can overwrite and damage other files on your drive. Use of MountImage is highly discouraged, even by Steve.
<ftp://mirror.aol.com/pub/info-mac/disk/mount-image-12b2.hqx>
MungeImage 1.2 by Peter N Lewis and Quinn "The Eskimo." MungeImage, a famous eight hour hack, works around MountImage's fragmentation problem by loading disk images entirely into RAM. It has a faceless drag & drop interface and can mount both DiskCopy and DART images, although only DiskCopy images can be mounted as unlocked volumes. Peter and Quinn have placed MungeImage's Pascal source code (which includes descriptions of DiskCopy and DART file formats) in the public domain.
<ftp://mirror.aol.com/pub/info-mac/disk/munge-image-120.hqx>
<ftp://ftp.share.com/pub/peterlewis/source/mungeimage-120-source.sit.bin>
Norton Floppier 3.2. This disk duplication and formatting component of Norton Utilities 3.2 only supports its own proprietary disk image format, but does provide an option to copy only used sectors.
MacTools FastCopy 4.0. This component of MacTools Pro 4.0 provides the same functionality as Norton Floppier, but supports Apple's DiskCopy image files and its own compressed image files (which use Stacker's proprietary compression algorithm).
DiskDup+ 2.7 by Roger Bates. This utility excels at disk duplication, sporting options to ignore unused or bad blocks and even copy 800K images onto 1.4 MB media with increased free space. DiskDup+ supports reading and writing Apple DiskCopy images as well as its own DiskDup+ image file format, and will mount image files after you pay the $25 shareware fee. Roger also has a commercial version called DiskCopy Pro that supports removable media larger than floppies.
<ftp://mirror.aol.com/pub/info-mac/disk/disk-dup-plus-27.hqx>
Disk Charmer 3.0.2 by Fabrizio Oddone. This $10 shareware utility's claim to fame is its ability to read, write, and format floppy disks in the background using asynchronous I/O and the Thread Manager. Copies take a little longer, but the ability to switch to another application and perform another task while you read or write DiskCopy disk images can be a real boon.
<ftp://mirror.aol.com/pub/info-mac/disk/disk-charmer-302.hqx>
ShrinkWrap 2.0.1. (I know this is my own program, but I never claimed to be unbiased!) This utility reads, writes, mounts, and converts a variety of images files for volumes of all sizes, including new self-mounting image files that can mount or save themselves back to disk. Designed around a drag & drop interface, ShrinkWrap also provides an menu-driven front end and a full-featured Apple event suite. It handles integrated compression, encryption, and encoding through Aladdin's StuffIt Engine and has a batch mode that speeds large jobs. ShrinkWrap is freeware, but with a $20 shareware fee for commercial use.
<http://www.halcyon.com/shrinkwrap/>
<ftp://mirror.aol.com/pub/info-mac/disk/shrink-wrap-201.hqx>
CryptDisk 1.2.1 by Will Price. This $20 shareware tool is designed for disk image users who take encryption very seriously. Although CryptDisk doesn't read or write image files to disk, it does create and mount soft partitions of any size that are encrypted using IDEA (International Data Encryption Algorithm) encryption. IDEA uses 128-bit keys and is generally recognized as secure. The full version of CryptDisk is available for U.S. and Canadian citizens; a demo without encryption is available to anyone.
<http://www.primenet.com/~wprice/cdisk.html>
DropDisk 1.0b5 by Chris Cotton and Mike Wiese. Originally released as Mount 'em, Chris and Mike leveraged much of the work done to mount PC drive containers for Apple's DOS card with PC Exchange to overcome the problem with fragmented disk image files and mounting disk images from a network. However, the application has only a drag & drop interface and can't mount DiskCopy images unlocked.
<ftp://ftp.info.apple.com/Apple.Support.Area/Developer_Services/Utilities/DropDisk.sit.hqx>
Disk Image Mounter 1.0.1 by Apple. This direct descendent of DropDisk was given a simple front end, modified to support New Disk Image Format (NDIF; see below) images and DiskScripts (batch files for mounting disk image sets), then packaged with the PowerBook 5300s. It only supports mounting disk images as unlocked volumes.
<ftp://ftp.support.apple.com/pub/apple_sw_updates/US/mac/utils/Disk_Image_Mounter_1.0.1.hqx>
DiskCopy 6.0.1 by Byron Han for Apple. DiskCopy 6.0.1 will be a complete rewrite of DiskCopy, supporting copying, creating, converting, and mounting DiskCopy 4.2 and NDIF disk images. It will also add support for AppleScript, log files, CRC-32 checksums, DiskScripts, and digital signatures. Currently, DiskCopy 6.0.1 is currently only available for Apple internal use.
Some Fuzzy Images -- I should point that some installers don't play well with disk images: the most notable are from Microsoft and Connectix. Many of Microsoft's installers simply don't check if the next disk is available before ejecting the current disk and prompting the user to insert a floppy. Of course, "reinserting" a mounted disk image from a modal dialog is practically impossible. Connectix's installer, on the other hand, is clever enough to determine if it's being run from a physical floppy disk and forces the user to quit if that's not the case, probably as an attempt to deter piracy. Of course, you can work around these installers by copying disk images to floppy disks and running the installer the old fashioned way, but that's not as convenient.
Additionally, developers usually take two approaches to mounting disk images: RAM-based and file-based. A file-based driver mounts image files by accessing blocks directly from a local hard drive or a network server; conversely, a RAM-based driver mounts an image file by dynamically creating a RAM disk and then copying the contents of the image file to the RAM disk. Although the RAM disk eventually makes for faster performance, mounting the image takes longer and you must always have as much free RAM as disk capacity you wish to mount. (Sorry - virtual memory doesn't count!) File-based drivers typically use only about 1K of RAM per mounted image, but they're slower and can be confused by background compression utilities like AutoDoubler or StuffIt SpaceSaver. Currently, all the utilities mentioned above except MungeImage use file-based drivers, although ShrinkWrap supports both techniques.
Versions of Apple's DiskCopy prior to 6.0.1 have a problem with occasionally incorrectly calculating checksums for tag data. Tag data is an extra 12 bytes of "scavenger" information for each block on 400K and 800K floppies. It was mainly used to embed copy protection information and data recovery hints back in the old days of half-tracking and other such whimsical annoyances. Since the 660AV and 840AV Macs can't even read tag data, many disk image utilities and disk image formats safely ignore it.
New Disk Image Format -- With the glut of alternative disk image file formats available, you may find it surprising that the original DiskCopy format still dominates online. Well, aside from the disadvantage of having to compete with the officially endorsed Apple image file format, many of the "improved" image file formats fall short of DiskCopy in critical areas. For example, compressed image files or images that don't contain copies of unused blocks can't be mounted on the desktop as unlocked volumes. What's more, many simplified file formats lack critical information like checksums and tag data that may be critical to identifying data loss or satisfying some copy protection schemes.
However, there are some simple ways the present DiskCopy image file format can be improved, and the New Disk Image Format (NDIF) supported in Disk Image Mounter 1.0.1 and DiskCopy 6.0.1 is Apple's attempt to do just that. This new file format comes in three flavors, Read/Write, Read-Only, and Read-Only Compressed, enabling the user to optimize the image file for flexibility, speed, or size. All NDIF flavors use industry standard CRC-32 checksums, and none waste space saving tag data.
Unfortunately, all the advantages of the NDIF format are offset by the fact that it presently only uses one compression scheme, an Apple proprietary codec named KenCode. Because of this restriction, no other commercial, shareware, or freeware utilities can legally read or write NDIF compressed image file formats without licensing the KenCode libraries from Apple. There have been overtures from Apple promising these libraries will be released to the general public at no charge, but I've seen no progress in this effort since November of 1995.
Your Mission -- Has the time come to throw away your floppies? For many Mac users, the answer is definitely yes. One batch session with a good disk image utility can reduce a rat's nest of floppy disks to a manageable archive on removable cartridge or CD-ROM that you can take on the road and share over local networks or the Internet. Software installations from mounted disk images can save countless hours, especially for MIS managers, testers, and service technicians who configure new machines daily. So, find a utility that suits your tastes and discover the power of disk images!
Non-profit, non-commercial publications and Web sites may reprint or link to articles if full credit is given. Others please contact us. We do not guarantee accuracy of articles. Caveat lector. Publication, product, and company names may be registered trademarks of their companies. TidBITS ISSN 1090-7017.
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