Previous Issue | Search TidBITS | TidBITS Home Page | Next Issue

TidBITS Logo


Communications upgrades fill this issue, with a letter about how the ARA server 2.0 won't work on a Mac Plus and articles by Mark Anbinder on a minor upgrade to CE's QuickMail Server and a major upgrade to the popular FirstClass BBS program. Readers explain in detail how MTBF testing works, and we pass on a warning about how MacInTax might be calculating your taxes.


Copyright 1994 TidBITS Electronic Publishing. All rights reserved.
Information: <> Comments: <>

This issue of TidBITS sponsored in part by:


Our apologies if we haven't responded to email sent to us late last week. We were in Indianapolis days talking with the folks at Hayden about various books and explaining to the publishers of the different Prentice Hall Computer Publishing imprints about what the Internet is about. Email piled up, and we're still catching up.

Another minor pileup in email might occur next week, because we'll be in San Rafael and the Bay Area on 21-Apr-94 to sign copies of our books at the Borders store in San Rafael and at a Stacey's bookstore somewhere else in the Bay Area. We'll have more details next week, but the Stacey's signing is in the afternoon and the Borders one is in the evening. We'd love it if people came by and rescued us from author hell, which is sitting at a table with stacks of books and people stopping by to ask where the travel books are located.

Jack Mello <> reported his frustrating experience after updating a Mac Plus from ARA 1.0 to 2.0 and attempting to configure the settings: "This caused the machine to give me a Finder error. The only option was to hit the Restart button in the error dialog. Assuming that the problem must be with the installation I cleared out the ARA files and tried the installation again, and again! By the third time I was pretty certain that I had my end right. At this point I laid my hands on the phone and typed out the Apple SOS phone number."

The support person at the other end of the SOS line confirmed the problem and suggested it might be a conflict with the Plus's ROMs. Although the first person Jack spoke to mentioned that a fix or patch might be forthcoming, a fix hasn't shown up yet. You might be wondering what the big deal is, what with the Plus being so old, but in many ways - and especially for organizations on limited budgets - an old Plus is the perfect choice for a server. Jack wasn't sure about whether or not the client version of ARA 2.0 works on a Plus, but it would be worth checking on.

MTBF Revealed

We commented last week that we didn't know how that increasingly large mean time between failure (MTBF) number is calculated for hard drives. Luckily, the beauty of having so many knowledgeable readers (and a few comedians) is that we receive good answers to such questions.

Luca Accomazzi <> suggests helpfully:

I may have an answer about how to determine a MTBF of 500,000 hours. Buy 500,000 drives and turn them on. Watch and see how many die in one hour. If only one does, then you have a MTBF of 500,000 hours. Check to make sure that you have an ample supply of plugs before you try that at home, though.

E. Warwick Daw <> writes:

I don't know for sure how drive manufacturers do it, but the methods usually used for things like this are called "survival analysis." If you really want to know all the details, I'd suggest looking in the statistics section of your library for the theory, and then the industrial engineering and medical research sections for the applications. The basic idea is that you take 1,000 hard disk drives, turn them on, and let them run. Now, since MTBF is only an average, even if you have a very long MTBF, if you have enough drives, you will expect to see a few failures relatively quickly. So, say 5 of your 1,000 drives fail in six months of testing. You take your data and, making certain mathematical assumptions, you fit a "survival curve" (a plot of the number still working vs. time) to it. From this curve, you can calculate a predicted MTBF based on your mathematical assumptions.

As a pure mathematician turned applied mathematician, I am quite skeptical of claims of a half-century MTBF based on a few months of testing. IMHO, the usual mathematical assumptions about how complex mechanical devices wear out just don't apply over decades, but I can't really judge the methods used by the drive manufacturers without examining them closely.

In any case, although I take MTBF ratings with a grain of salt, I do still consider them useful, and, all other things being equal, I would get the drive with the higher MTBF. Just realize that what the MTBF represents is the chance that the drive will crash in the first year you have it, and not the total lifetime of the drive.

Caesar Chavez <> explains:

I have been out of the "reliability business" for a few years. But I may be able to provide you with some information regarding disk reliability.

Disk drive reliability from the mid-70s to the mid-80s improved by a factor of five, from 10,000 hours to 50,000 hours. I didn't realize that their reliability has improved so dramatically in the last few years. You are right in that engineers have discovered a way of testing hardware in an accelerated way.

In order to derive MTBF numbers, some assumptions are normally made. First of all, a level of ambient temperature is assumed, usually room temperature with cooling and/or fans providing air flow. Second, the devices are not turned off and on often. Third, mechanical parts are guaranteed to be lubricated properly. Fourth, oftentimes the devices are "burned in," which means they were run while cycling power and temperature for a time in order to "shake out" weak devices, defining the term "infant mortality." Fifth, a semiconductor part is assumed to receive all signals and power within narrow tolerances. Under these ideal conditions, a manufacturer can provide an MTBF number for a device.

These specifications provide the key for accelerated testing. Military and aerospace standards, which by necessity require extremely high reliability numbers, typically state that for each 10 degrees of temperature rise, parts will fail at some extrapolated rate. If memory serves me correctly, if mechanical or semiconducting devices specified to be operated at 20 degrees centigrade are operated at 50 degrees centigrade instead, they will fail three times or eight times as often respectively. An electromechanical device such as a disk drive, under elevated temperature, will fail at a much higher rate weighted by the amount of electrical versus mechanical parts contained in it. Therefore, reliability numbers may be derived by running a device at an elevated temperature for a much shorter period of time than would normally be required in order to generate failure rates under normal operating conditions. In addition, power cycling may be used to accelerate failures; sometimes signals and power input or output may be operated outside of normal manufacturer-specified operating conditions. Application of these failure-inducing processes to MTBF rates is called "derating" a part under stress.

NASA and the Department of Defense have spent billions of dollars and years to verify their conclusions. As you stated, for the normal, non-military user, if a device is run under normal operating conditions in terms of temperature, power, and power cycling, quality commercial-grade disk drives should last for a long time.

John Woods <> confirms:

In most cases, the manufacturers run their MTBF tests at elevated temperatures and voltages, having determined through empirical tests the relationship between how fast you accelerate the failure of key parts if you exceed the specs by just how much. They also do some analysis from the MTBF of individual components (sometimes learned from the previous method) and calculate the system MTBF accordingly. Some manufacturers may be just guessing, though...

I pay much more attention to the warranty period than to the MTBF, since the warranty period isn't a guess or a statistical prediction, it's a promise. A 57-year MTBF coupled with a 1-year warranty sounds as though the company in question isn't all that sure of its MTBF figure.

Rich Straka <> provides more details:

First, a little explanation on failures. There is a general concept of failures that breaks them up into three categories:

The "Bathtub Curve" is a plot of the general failure rate of some component or system:

    Failure rate
        Infant           Everything              Wearout
        Mortality          Else
  High  |\                                         /
        | \                                       /
        |  \                                     /
        |   \___________________________________/
  Zero  |___________________________________________________

MTBFs -- System MTBFs are tricky things to begin with. I would assume that there are all sorts of ways of coming up with them. Their reliability as a measure of quality is highly dependent on the ethics of those who determine them and quote them.

One way is to measure the failure rate by firing up a lot of units and waiting a long time for failures to occur. Infant mortality is not counted (for obvious reasons). Wearout failures are not usually counted either. For example, muffler MTBF is relatively low (if, indeed anybody even considers such a figure), but muffler wearout is relatively common and predictable. These are not the same things!

Another way is to come up with a composite MTBF, comprised of the individual MTBFs of all of the components of the system. I'm not up on the math typically used for this assessment. Each of the components, of course must have a properly assessed MTBF.

For any MTBF, operating environments (temperature, voltage, etc.) must be specified. For hard disks, it's not clear if they ever power cycle them, for instance. I suspect not, and that's the subject of another conversation.

Accelerated Testing -- Instead of waiting around for failures, it is possible to characterize a type of failure (electromigration, sodium contamination, etc.) of individual components based on operating temperature.

A Swedish chemist and physicist by the name of Arrhenius developed an equation stating that many chemical and physical processes are governed by temperature, where the speed of reaction of a process is proportional to the natural antilog (e to the power) of some constant times the absolute temperature.

In order to determine the acceleration of the reaction rate of a process, you calculate the rates for the two temperatures of interest and divide them. The actual numbers are of little interest, the ratio is what is important here.

This constant is known as the device's "activation energy," which is specified in units of electron-volts. Common values are 0.7 - 0.9 eV, which is a big range (being up in the exponent).

Most folks in the quality business do tests (testing failure rates at different temperatures) to determine a device's activation energy.

With this information in hand, they can then test devices at high temperatures to simulate long service times. They calculate the acceleration factor for a particular temperature from the Arrhenius equation, enabling them to test many years' worth of wear in just a few weeks. This is how we used to test the data retention parameters of EPROMs back in the late 70s.

CE Fixes QM Server

by Mark H. Anbinder, News Editor --

Director of Technical Services, Baka Industries Inc.

Late last month, CE Software, Inc. announced a new release of its QuickMail electronic mail server software, version 2.6v2. The update, which affects only the server software, fixes two problems in previous versions.

CE reports that, when messages with large file enclosures were forwarded from one user to another, other local users were sometimes disconnected from the server. CE also corrected a problem that prevented the 57th and 170th users defined in any given MailCenter's user list (alphabetically) from connecting to the server remotely using the QM Remote utility.

CE will distribute new QuickMail packages with the fixed software. CE customers who pay for premium support will receive a disk-based updater. Other customers may download an updater from CE's support forums on America Online, CompuServe, and AppleLink, or the Internet from:

QuickMail users without Internet or online service access may request the update on disk for $10 by calling CE Software.

The updater utility works on existing installations of QuickMail server software 2.6 or 2.6v1. CE released a 2.6v1 updater a few months ago. There have also been 2.6v1 updates for the QuickMail client software, the QM Administrator application, and the NameServer control panel since QuickMail 2.6 was released last year. You can find at least some of the previous updaters in:

CE Software, Inc. -- 800/523-7635 -- 515/221-1801
515/221-1806 (fax)

MacInTax & Common Cents

by Tonya Engst, TidBITS Editor --

If you live in the U.S. and haven't yet filed your tax return, chances are you're planning a small adventure in accounting in the next few days.

If you use MacInTax, be aware that the program pinches pennies differently from last year. ChipSoft modified MacInTax so that it only uses the Whole Dollar Method (where you round entries on the forms and schedules to the nearest dollar, instead of entering in the actual dollars and cents amount). It seems that the initial release of MacInTax not only did not allow you to enter pennies on the main 1040, it also truncated the amount. In response to what appears to have been a fair amount of customer outcry, ChipSoft released MacInTax 11.01b, which instead of truncating, rounds the dollar and cents amount that you enter on the 1040. To acquire 11.01b (or more likely, the latest revision, 11.01c), call the 800 number below. Expect about a week to receive the update unless you want to pay the Fed-Ex charge yourself. Sorry, you can't update via modem or the nets.

If you want the rounding capabilities in 11.01b, but don't yet have the update, Mark Goines, ChipSoft Director of Product Marketing, suggests the following workarounds:

Some people want to enter pennies on their 1040s, a perfectly legal practice. The ChipSoft response on their CompuServe forum was that the pennies option was removed by request of the IRS. A call to tech support revealed additional possible reasons for the software change. According to Bunny Bedell, the Whole Dollar Method helps to speed up the program and reduce memory consumption. Bunny's take on the situation was that next year's MacInTax will probably let you enter pennies, if you wish. Bunny also commented that from the IRS's perspective, rounded amounts are simpler to work with.

Ed Fortmiller <> points out that "the problem with this approach is that it doesn't allow the user to optionally retain the cents, which in some cases results in users paying more than the legal minimum tax. The higher tax results when rounding to achieve the Whole Dollar Method pushes the user who uses the tax tables into the next higher grouping. For instance a single person with an income of $49999.99 would pay $14 more tax using MacInTax since the income would be rounded to $50,000 thus pushing the person into the next higher $50 group."

Mark acknowledged the problem, and pointed out more specifically how the problem could occur, saying that you would only be moved to $50,000 and thus incur the $14 more in tax if you took only the standard deduction. If you itemize deductions, as 84 percent of MacInTax users did last year, you likely would not be pushed into the $50,000 level.

Although it looks like many of the problems could be fixed by itemizing or paying attention, a quick read of the CompuServe forum for ChipSoft reveals a number of examples of people penalized by not being able to enter cents, so if you use MacInTax, you'll want to be aware of what you do with your pennies.

On a related note, although my contact with ChipSoft about the problem was entirely positive (Bunny at tech support acknowledged the issues involved and Mark Goines promptly wrote back with clarifications), Ed had much worse luck in feeling that ChipSoft cared about his problems with the lack of being able to enter pennies - and based on my quick tour through the CompuServe forum, I see why. Responses were generic and corporate and gave little sense that the company cared about its customers - whether or not removing the feature was a good business decision in terms of improving the program, failing to be sufficiently sympathetic in an area as charged as tax filing is a guaranteed way to lose customers to the competition.

ChipSoft -- 800/964-1040 (sales) -- 602/295-3080 (support)
Information from:
Ed Fortmiller <>
Bunny Bedell, MacInTax Technical Support
Mark Goines, ChipSoft Director of Product Marketing

FirstClass 2.5 Ships

by Mark H. Anbinder, News Editor --

Director of Technical Services, Baka Industries Inc.

Better late than never, say owners of Soft-Arc's FirstClass messaging software. SoftArc shipped the long-awaited FirstClass 2.5 at the end of March, making it available to existing customers immediately on SoftArc Online, their own FirstClass server. Customizable message forms, enhanced email functions, and database access are among the highlights of the new release.

FirstClass is popular as BBS software for companies providing technical support, as a corporate email and conferencing system, and even as the base software for professional-looking local bulletin boards. FirstClass supports email and other basic messaging features at its core, along with threaded discussion capabilities, file transfer, database access, and online chatting.

Although SoftArc originally intended to ship the release in late 1993, they delayed the release in order to respond to beta testers' reports and suggestions. Nick Chinn of Global Village Communication, which uses FirstClass to provide support, information, and software updates to customers, says he's "always happy when a developer admits there are bugs in the software and is not willing to release the product until it is ready. Extended beta testing periods also let a developer add overlooked features based on feedback from customers."

In addition to sharing administrator functions on Global Village's support BBS, Nick is the admin or co-admin on two other systems, including a public BBS operated out of his home. One important improvement 2.5 provides is the ability for multiple connection schedules and automatic retries of failed connections for server-to-server gateway links. This is important to Global Village "because we like to get our support conference questions answered quickly and then transmitted out immediately."

FirstClass 2.5's directory synchronization capability stands out as one of its sexiest features. Large organizations can use multiple FirstClass servers spread over several local-area networks, linked by routers, WAN connections, or even on-demand modem links, and keep a consistent user directory on each server. Mail sent to a user is automatically earmarked for the correct server and properly routed, whether over a traditional network connection, dialup connection, or other link. SoftArc says that even with as many as 100,000 defined users, the FirstClass server quickly completes directory searches and name matches.

For larger networks, such as the international OneNet network that has sprung up based on the FirstClass architecture, servers can exchange only routing information rather than entire directories. Each server sends its neighbors the list of other servers it knows about and can reach. This means that users must provide the user name and site name for an intended recipient, but FirstClass automatically determines how to best route the message to its recipient. The FirstClass name-matching feature works even at a distance; users need only provide enough of an intended recipient's name to match it uniquely at the destination site. If there isn't a unique match, the destination site returns a list of "hits" so the sender can try again.

Other email functions SoftArc introduced include: automatic message forwarding (even over an Internet or fax gateway), auto-replying, and message receipts (which can indicate when the message was routed, delivered, or read). SoftArc is also shipping its forms editor, allowing administrators to create customized message forms or edit existing ones. This meshes well with the "stationery" capability, permitting administrators to set up pre-addressed forms that users can fill out and send with a minimum of effort.

FirstClass 2.5 also offers impressive new database access features. Third parties are already providing database query extensions to permit FirstClass users to access SQL and DAL databases. EveryWare Development Corporation offers 411 for FirstClass, which can access the company's multi-user Butler SQL database server, and TGF Technologies has shipped FirstConnect to access DAL-compliant database servers. The FirstClass database API is sufficiently flexible that it's likely to spawn a suite of Internet information access products in the future.

Usenet readers should be particularly interested in the improved non-delivery notification handling with gateways. As more and more FirstClass systems connect to the Internet with a gateway, incorrect configuration has on numerous occasions led to "NDN" messages sent to unsuspecting, and understandably frustrated, Internet users. By default, FirstClass 2.5 suppresses conference error messages when a gateway is involved; bounce messages will of course still be sent when messages to individual addresses are undeliverable.

SoftArc says the new version incorporates speed increases for modem connections and wide-area networks, and in particular for file uploads. At the same time, the server and client software encrypts all packets regardless of the communications medium, so all messages, files, and login transactions are exchanged in a secure manner.

One area still lacking in FirstClass is its command-line user interface, or CLUI. Although this feature (an option on corporate mail configurations) enables anyone with a VT-100 terminal or emulator to access a FirstClass server, it lacks the elegance of the Macintosh and Windows graphical interface software. Many first-time users "find it difficult to navigate," according to Nick Chinn, who would like "some degree of ability to custom configure the CLUI interface."

An immediate project for SoftArc now that FirstClass 2.5 has shipped will be to take the DOS client software off the back burner and do some serious work. A DOS client will give an alternative to the vast majority of users now restricted to the CLUI. SoftArc also plans to build TCP/IP support directly into the server and client software; currently, TCP/IP connections can be arranged only through the software's built-in support for the Communications Toolbox, using third-party MacTCP-compatible connection tools.

The FirstClass Client software is available for Macintosh and Windows users, and you may download it from America Online, CompuServe, or SoftArc Online (416/609-2250). It will no doubt appear on the Internet soon. Registered owners may download the new server software directly from SoftArc Online or may order a $95 upgrade package that includes a complete set of disks and documentation. (SoftArc completely rewrote their comprehensive manuals for this release.) At this time - because the documentation is being printed - SoftArc is shipping FirstClass server 2.4.1 and client 2.0.9 to new purchasers. If you buy the older versions, you will receive the 2.5 software and documentation for free.

SoftArc Inc. -- 416-299-4723 -- 416- 754-1856 (fax)
EveryWare Development -- 905-819-1173 -- 905-819-1172 (fax)
TGF Technologies -- 802-660-4911 -- 802-862-1890 (fax)
Information from:
SoftArc propaganda


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.

Previous Issue | Search TidBITS | TidBITS Home Page | Next Issue