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Review: Norton DiskDoubler Pro 1.1

by Michael Tsai,


[ndd0 graphic]

Last month I reviewed Aladdin System's Stuffit Deluxe package, and in the review, I made some comparisons to Symantec's Norton DiskDoubler Pro. I thought that it would be only fair to give this product the space that it deserves. Like Aladdin, Symantec has created a compression bundle of what used to be distinct products, although the Symantec package is significantly more versatile. In this case, the components are AutoDoubler, DiskDoubler, and CopyDoubler. AutoDoubler is an idle time compression program similar in intent to Stuffit SpaceSaver. DiskDoubler is an archive compression program similar to StuffitDeluxe. CopyDoubler is a batch copy accelerator and scheduler, similar to the SpeedCopy component of Connectix's SpeedDoubler. These products are at least as featured as their nearest competitors, so even if you already own a compression packages, read on.


DiskDoubler is very similar to StuffitDeluxe, but it has several important differences. It allows you to select which compression method you would like to use. You can choose between AD 1, AD 2, DD 1, DD 2, and DD 3. Higher numbered methods take longer to compress files, but save more space. The first two are methods that AutoDoubler can read, and are the fastest. On a PowerMac, expansion of these two methods is almost instantaneous. However, they only reduce the size of files by about 35%. The DD methods are significantly slower than the AD methods for both compression and expansion, though the higher numbered methods do not take longer to expand than the lower numbered ones. The first DD method is roughly equivalent to Stuffit Deluxe, both in terms of speed and of savings. DD3 is the tightest compressor that I have used, usually saving a few percent more than StuffitDeluxe. However, it is much slower, taking as much as twice as long as Stuffit to compress files.

There are two ways for the user to interact with DiskDoubler: Through the "DD" menu that is added the Finder (see below), and through the actual application. Unlike Stuffit, although tasks can be queued in the Finder, all the processing is done within the DiskDoubler application. This slows down response time because the application has to launch, but also frees up the Finder for other tasks.

[ndd2 graphic]

Also unlike Stuffit, DiskDoubler is not known for its elegant interface. Although it was the first compression product to allow the user to drag files into and out of archive windows, it only supports archive windows within the DiskDoubler application. And if you want to drag files from Finder windows, you have to open up the corresponding windows in the DiskDoubler application, and drag from within it. Now that Stuffit Deluxe offers True Finder Integration, it is hardly worth using the archival capabilities of Norton DiskDoubler Pro unless you are in a situation in which every last kilobyte counts. The only other real advantage that DiskDoubler has is its ability to queue jobs. This is something that I'd like to see in Stuffit Deluxe, and is very useful, especially when you want to compress or expand a large group of files.

Files can be expanded with the freely distributable DDExpand application, but unlike Stuffit Expander, not many people have this, so it is safer to make archives self-expanding.


CopyDoubler speeds up Finder copies by making more efficient use of system memory and processor time. Its main utility though, is its ability to place copies in the background, and to queue multiple copies. Both features are better implemented than in its nearest competitor, Connectix's SpeedCopy. Most of the time, background copies don't slow down the computer much, and queuing copies, rather than processing them all at once as with SpeedCopy, seems to make them proceed faster and use less screen space.

As you can see below, CopyDoubler also gives statistics about the throughput of the copy, and the estimated time remaining, which is generally very accurate.

[ndd3 graphic]

Unfortunately, the top portion of the collapsible CopyDoubler window is mostly taken over by the CopyDoubler graphic. No matter what size monitor you have, screen real estate is important. If the size of the dialog bothers you as much as it bothers me, you can rearrange it a little in ResEdit, and remove the space-consuming graphic.

CopyDoubler also allows the user control write verification with copies from different types of media, and can even play sounds to alert the user of a completed copy. One of its most useful features is the ability to schedule copies to occur at specific times. This is especially useful for automatic, no-frills backups.

Furthermore, CopyDoubler is integrated with AutoDoubler, and can compress and expand files that it is copying, according to the user's preference.


AutoDoubler can automatically compress all the files on your hard drive, except those in the System Folder, reducing them to about 50% to 70% of their original size. You can manually compress control panels and extensions in the System Folder with the AutoDoubler Internal Compressor, and can exclude certain folder, disks, and labels from automatic compression.

What makes AutoDoubler unique, is its transparentness. It is by far the best in its category in terms of speed. On 680x0 Macintoshes, applications seem a little sluggish when launching, but after that run normally. On a PowerMac, there is virtually no difference in speed between compressed and uncompressed files.

AutoDoubler achieves this magnificent speed by expanding only the portions of files that it needs. Unlike Stuffit SpaceSaver, it doesn't expand files to disk, but instead expands them, a piece at a time, to RAM. This prevents the hard disk from becoming fragmented, and improves performance. In addition, the user can select the size of the RAM cache, thereby increasing performance at the cost of memory.

Final Words

The product that we now know as Norton DiskDoubler Pro has evolved over the years. Once owned by Salient Software, it was known simply as DiskDoubler. Then it was acquired by Fifth Generation who released version 4.0 and combined AutoDoubler, CopyDoubler, and DiskDoubler into one complete package called SuperDoubler. More recently, Fifth Generation was acquired by Symantec who renamed it Norton DiskDoubler Pro, reduced the version number to 1.1, and made it PowerPC native.

Unfortunately, as Symantec acquired companies such as Peter Norton Computing, THINK, and Fifth Generation, their products' evolutionary cycles seemed to slow down. Norton DiskDoubler Pro, (which as far as I know had nothing to do with Peter Norton) has not been updated in well over a year, although two compatibility patches have been released for CopyDoubler. If Symantec does not come out with a new version soon, the DiskDoubler component, already considered non-standard, will be completely eclipsed by Aladdin's StuffitDeluxe.

The CopyDoubler and AutoDoubler components are still the best in their fields, and they alone can justify buying the complete package. Although, since the prices of hard disks has dropped so dramatically in the past year, the AutoDoubler component is no longer as necessary as it once was, but the extra space that it creates is always welcome. Despite the weakness of the DiskDoubler component, Norton DiskDoubler Pro is a useful utility package, well worth looking into if you are seeking background Finder copying, or extra storage space.

[08/98 Note: Most of Norton DiskDoubler Pro is incompatible with Mac OS 8 and later. Symantec no longer supports the product.]

[apple graphic] Michael Tsai is the Associate Editor for Reviews at ATPM. You can send any comments you have about this review to him at

Reader Comments (26)

Patricia Corrigan · January 14, 2001 - 01:01 EST #1
Where can I get a copy of DiskDoubler? I have some old files compressed with DD on a Mac Powerbook back in 1986. Now I'm not only on a PC but writing a book using those files. I have a friend with a Mac: Can you help?
Michael Tsai (ATPM Staff) · January 14, 2001 - 01:01 EST #2
DiskDoubler is no longer for sale. However, there is a free expander for it called DDExpand.

Also, Aladdin's StuffIt Expander claims to be able to expand DiskDoubler files.

anonymous · August 19, 2001 - 22:22 EST #3
I tried to download DDExpand but the archive was corrupted and wouldn't work. Is there another source for this application? Thanks, Ray
Michael Tsai (ATPM Staff) · August 19, 2001 - 22:43 EST #4
DD Expand is also available from Info-Mac.
Tomas Dieguez · November 6, 2001 - 06:35 EST #5
The DDExpand download is corrupt. Do you know another source? Stuffit Expander expands DDs but can't join DD segments, right? Tomi
Michael Tsai (ATPM Staff) · November 6, 2001 - 19:34 EST #6
The file at the above Info-Mac link works.
Danal Shapeno · March 14, 2002 - 20:59 EST #7
Is there still anyplace where I can download DiskDoubler or DDExpand
so I can expand some old files? I thought my Stuffit Deluxe 6.5.1 would
do it but it won't.
Lee Bennett (ATPM Staff) · March 14, 2002 - 22:35 EST #8
Danal - according to Aladdin's web site, you should be able to drag your DD file to Stuffit Expander and it will decode.

If not, I found version 4 of DDExpand in the Info Mac archives
John Persen · April 16, 2002 - 12:09 EST #9
How can I purchase Norton DiskDoubler via the Internet?
Lee Bennett (ATPM Staff) · April 16, 2002 - 13:57 EST #10
John - because Symantec officially discontinued it some time ago, you probably can't purchase it by any regular means. However, I just found a guy who has 12 unopened boxes and they're up for auction on eBay. I found it by typing "diskdoubler" in the search box.
Albie Garcia · July 23, 2002 - 12:44 EST #11
CopyDoubler had the ability to schedule files to be copied. Now, OS 9.2.2 is out for Mac. What can I use to schedule a file copy that won't cost me an arm and a leg?
Alan Slingsby · October 10, 2002 - 03:00 EST #12
I have a file that was segmented some time in 1993, almost certainly using DiskDoubler. Neither DD nor Stuffit will reunite the segments. File type is Tjcd and the creator is PNnb. Any ideas?
anonymous · December 10, 2002 - 06:01 EST #13
Can you tell me where I can find DiskDoubler Pro version 4.1? Thanks.
Lee Bennett (ATPM Staff) · December 11, 2002 - 19:15 EST #14
Count yourself incredibly lucky if you can find someone with an old box laying around or maybe on eBay, but I wouldn't hold my breath. It's been discontinued for years. The DDExpand I mentioned a few comments above is probably the only thing you're going to get your hands on. My suggestion: use it if you have DD archives you can't get into, then recompress into StuffIt files.
Paul Douglas Valentine · January 11, 2003 - 15:39 EST #15
DiskDoubler/AutoDoubler was--and still is, by far--superior to StuffIt. Norton's letting it die was idiotic.
The Star · August 14, 2003 - 12:50 EST #16
I think I am lucky I have the original that's still in working shape, but I can't use it on SoftMac. Most of my backup disks from then are 720kb. I can't seem to open them on SoftMac.

I dusted off my old Power Mac 6100 and now I can't remember the hard drive password. So, I went to my old LCIII and found it empty. I am installing SuperDoubler 1.01. I think that is the version. Now, I just need to update it. *LOL* What a day!
Robert Ahnlund · January 7, 2004 - 13:17 EST #17
Is there a DiskDoubler compatable with OS X.
Lee Bennett (ATPM Staff) · January 7, 2004 - 14:44 EST #18
Robert - I don't think so. The entire idea of automatic file compression has largely been abandoned because of the extreme hit against performance—the time required to decompress and recompress the files you work with. In addition, the price of file storage has gotten so cheap these days, it's not really even worth it to run auto compression. You can move less frequently used data to CDs and DVDs and bigger hard drives can be found for well under a dollar per gigabyte.
Mike Van Hine · April 2, 2004 - 13:06 EST #19
Hey Allen,

I see your comment above about segmented files, I've got the exact same problem. Did you ever solve it? If so can you share the solution with me at

Jose Luis Bazo Barba · April 23, 2004 - 13:02 EST #20
Since I started using Macs in the late 80s DiskDoubler was number 1, until OS 8 and then 9.22 came along and I still tried to use it, DiskDoubler still works on these two systems, the only thing that I recommend is if you guys out there want to still use this software, install everything "but" the extension "DD menu" because it will appear in your menu bar but every time you click on it your Mac will crash.

iI was sad to know DiskDoubler no longer exists, and is hard to let go like all things we use for many years,but it's time to move on and the solution for me was to get Stuffit Deluxe for 9.22 and OS X. Hope this is helpful.
Sue · December 17, 2004 - 13:31 EST #21
I am trying to open my old Disk Doubler Files backed on CD..they will not open with DD expand or DD..any CD corrupt?..and what can be done to solve that problem
Thanks Sue
Laura Vaughan · January 9, 2005 - 06:44 EST #22
Just a note to say thanks to Lee Bennett and everyone for the information about the download of DD Expand. You've just enabled me to access my research which I stupidly backed up as diskdoubler files in 1999.

thanks again!

Kent Durvin · June 1, 2005 - 15:10 EST #23
DD Expand still works in Classic under OS 10.4.1, but some files will not expand. It works better on OS 9, if you can reboot in 9. Classic is not quite the same as actual OS 9.
Geoffrey Keating · May 20, 2006 - 17:08 EST #24
Thanks for the heads up on DD Expand. I was able to recover files I thought long gone. It gave me no real problems opening up in Classic, so hopefully no one else should have any problems.
Thanks again.
David Reindl · December 23, 2006 - 18:47 EST #25
Just if anyone coming along here searching for what could have produced files with type Tjcd and creator PNnb: it's Norton Backup.
Mark Bult · March 17, 2009 - 01:12 EST #26
I tried for years to find a way to decompress old DiskDoubler files on OS X, to no avail.

Finally I found a copy of DiskDoubler from 1999 and installed it on my G4 running OS 9 on top of OS X. Works like a charm.

Since DD is incredibly hard to find online (impossible for me, I finally got it off an old backup CD-ROM), I've uploaded it here to share with anyone else who had this problem:

DiskDoubler Pro 4.1 for Mac OS 9
It's at the bottom of the article.

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