Originally published in the February 1995 issue of Advanced Systems.


Comparison: Laptops

Taking it all with you

The pros and cons of SPARC-based mobility.

By Curt Aubley

By definition, workstations boast powerful CPUs, fast graphics, big screens and disks, built-in high-speed networking, and weighty multitasking operating systems. Laws of nature and today's technology conspire against the very idea of a mobile workstation. Despite the difficulty of the task, Tadpole Technology and RDI Computer Corp. have been designing and building SPARC-based portable computers for the last few years. Each company takes its own path in answering the question, "What trade-offs are mobile workstation users willing to accept?" (For Sun's answer, see the review "Voyaging into rough waters," April 1994.)

We brought the latest portable SPARC offerings from RDI (PowerLite) and Tadpole (SPARCbook 3) into the lab and on the road for a test drive to help determine just that. (Editor's Note: Despite numerous promises, IBM failed to provide its PowerPC-based RS/6000 N40 notebook for inclusion in this review; we hope to look at this and other portable RISC systems in future issues. See the sidebar Why not use a PC-class notebook?) The two systems varied slightly in their configurations. Both provide an excellent overall SPARC environment to bring on your travels. What initially distinguishes the two systems is the tremendous display and ergonomics the RDI PowerLite possesses versus the smaller footprint, lighter weight, and better overall system integration of the Tadpole SPARCbook 3.

What's inside
It is always fun to dissect vendors' products. Both of these portable systems are centered around the Texas Instruments 50-MHz microSPARC version 8 with a Harvard architecture cache design that incorporates only a 2-kilobyte data cache and a 4-kilobyte instruction cache. The corresponding SPARC reference Memory Management Unit (MMU) contains a meager 64 contexts. This configuration for the main CPU is a little dated when compared with current microSPARC II and SuperSPARC architectures. Both Tadpole and RDI plan to move to the microSPARC II CPU architecture; RDI's forthcoming PowerLite 85, to be available by the time you read this, will also pack a TGX graphics accelerator. (See "Mo' mobile computing," page 11, for more details.)

While the portable SPARC systems share many design goals, they use distinct approaches. The RDI PowerLite system arrived configured with two 360-megabyte internal SCSI-2 hard drives, 32 megabytes of RAM, a 10.4-inch, 1,024 by 768 active-matrix Thin Film Transistor (TFT) LCD color display, a single 312-inch floppy drive, and Solaris 1.1.1 pre-installed (Solaris 2.3 is available as an upgrade) -- all housed in a 2.2- by 12.75- by 11.18-inch black case weighing 812 pounds. The accessories package provided two RDI-specific user guides, a Solaris 1.1.1 (SunOS 4.1.3) manual and CD, an I/O breakout cable (for access to two DB25 RS232C and one DB15 AUI network connectors), a 13W3-to-VGA adapter, a Virtual Workgroup Architecture (VWA) CD-ROM, and a nylon carrying case.

The PowerLite's extensive expandability allows it to come close to that of your desktop, accepting two 32-bit SBus cards, RAM upgrades to 80 megabytes, and up to 1.56 gigabytes of hard drives (sans floppy drive) in its standard housing. For those who need even more computing resources, RDI offers a Peripheral Expansion Unit (PEU) that allows for an additional two SBus slots and another two 312-inch (1.2 gigabyte) hard drives. Snapping into the bottom of the PowerLite, the PEU adds 112 inches of thickness and 5 pounds of weight (for a grand total of 1312 pounds with the nickel-cadmium battery pack).

The Tadpole SPARCbook 3 arrived with a single removable 520-megabyte SCSI-2 hard drive (but no floppy drive), a smaller, lower-resolution 9.4-inch 640 by 480 TFT active matrix LCD, and Solaris 2.3 pre-installed. All of this hardware is housed in an amazingly small 2- by 11.8- by 8.5-inch magnesium alloy case weighing a mere 612 pounds -- including the battery pack. Accessories included two nickel-metal-hydride (NiMH) batteries, external battery charger, AC power supply, Solaris 2.3 and Solaris 1.1.1, vendor-supplied CD-ROM with NCE (Nomadic Computing Environment) software, and a nylon carrying case.

Since the SPARCbook 3 includes two batteries and requires only one for operation, users can extend the system's untethered life by swapping in a fresh battery as needed. There is no need to create space for the external battery charger when traveling -- it is roughly the size of two of the 12- by 1- by 14-inch batteries side by side and fits comfortably in the SPARCbook 3's small carrying case. The charger connects between the SPARCbook 3 and the external power supply, thereby allowing both the internal and external battery to recharge concurrently while the SPARCbook 3 is plugged into an AC outlet.

The system's RAM is user-upgradeable to 64 megabytes and the 212-inch form factor removable SCSI-2 hard drive up to 810 megabytes. The SPARCbook also boasts support of either two Type-I/II or one Type-III PCMCIA card. PCMCIA is classically associated with the PC notebook world, but Tadpole has created drivers to support a variety of PCMCIA products, such as IBM PCMCIA modems and Maxtor hard drives (130, 170 megabytes), with their SPARCbook 3. The SPARCbook 3 is limited in its upgradeability compared with the PowerLite, but we found its small size and weight to be a plus for the professional who frequently carries a system from site to site or works in cramped quarters (such as an airplane).

Getting started
Turning on both machines brought us directly into their respective initial diagnostic tests and to the system login prompt. While the RDI has the traditional power on/off switch plus the stop-key-plus-a-key combination for entering firmware mode, the SPARCbook provides only a single power-on button and no power-off switch. Tadpole instead lets users turn the system on and off via a pause-key-plus-o-key combination.

The SPARCbook 3 and the PowerLite feature extreme contrasts in their ergonomic design. RDI chose to manufacture a slightly larger and heftier system that's more laptop than notebook. But in this relatively roomy space, RDI engineers placed a larger 10.4-inch display with .20mm dot pitch, a full-size Sun-5-compatible, 104-key keyboard, and a three-button 16mm integrated trackball with ample palm space. The high-resolution screen is equipped with an 8-bit graphics system that supports 256 simultaneous colors from a palette of 512. Active matrix means color images show up brilliantly -- an important concern if you have one or two people looking over your shoulder for a demonstration.

Although it is possible to configure an external keyboard, the PowerLite's familiar Sun-5 keyboard makes this chore unnecessary. An external display up to 1,152 by 900 pixels can be configured through either the PowerLite's autosensing mode or through firmware. Unfortunately, the firmware in our PowerLite's PROM was not current and did not work in the autosensing mode. But with support from RDI's customer service, the external Sun monitor worked flawlessly. Using the integrated trackball seemed almost natural (but may be less so for people with particularly large hands), and felt very similar to that of Apple's original PowerBook notebook computers. However, the positioning of the three mouse buttons did take some getting used to.

Tadpole had to make some sacrifices with the SPARCbook 3 to gain its significant size and weight advantage. To enhance its smaller and lower-resolution screen (9.4-inch, 640 by 480), Tadpole allows users to zoom in and out of the display. When zoomed to the expansive out position, the overall picture is nice, but working with text in this mode can stress the eyes and is not particularly impressive when giving demonstrations.

The keyboard layout resembles that of a PC-style notebook. Tadpole uses Lexmark's 84-key configuration with three mouse-click buttons and an integrated pointing stick similar to that found on the IBM Thinkpad notebook. The pointing stick did take some getting used to, but it proved valuable in the cramped seat of an airplane. Tadpole provided a friendly interface through its Open Look-based NCE, which let us connect the SPARCbook 3 to my Sun monitor in a snap.

Mobile net
Mobile computing is networking in its truest form. If it's connecting to a new LAN, calling your home server, configuring your mobile SPARC computer into an Ethernet-to-PPP/SLIP gateway to boost remote connectivity, or just for basic office necessities, both systems offer an abundance of options for connecting to the outside world. Both include internal V.42bis, 14.4 kilobits per second data/fax modems based on the Rockwell 144 ACW chipset, two serial ports, network connection options (10BaseT and AUI for the RDI and AUI for the Tadpole), external SCSI-2 adapters, and a single parallel port. (See the panel diagrams on this page.)

The PowerLite system came installed with the Virtual Workgroup Architecture (VWA) software. Starting VWA was as simple as pulling down the Open Look root menu and selecting VWA. For friendly network configuration, VWA provided a set of simple tools that set both your IP address and NFS mounts/ shares, fax, and remote mail hosts. After letting us configure several different network settings for some of the various sites where we commonly work, the PowerLite used an autosensing mode upon bootup to automatically configure the NCR 89C100/7990-compatible Network Interface Card and the associated system files for a seamless new network connection. The PowerLite also comes with Andataco's XpressFax installed, so you can communicate with less technically advanced environments; and users adept with the Unix cu or tip utilities should have little trouble dialing into remote sites.

Similarly the SPARCbook 3 came installed with custom NCE software for administering the notebook. This Open Look-based GUI is actually the real command center of the notebook and tightly integrates the entire system. Through this interface, users can easily control such functions as network setup for both local Ethernet connections and serial SLIP connections. This feature will be appealing to users commonly on the road, where the time saved getting a remote TCP/IP-based connection up and running is greatly appreciated. Other areas you can control through the NCE command center include electronic mail hosts, power management features, external display definitions (VGA screens up to 1,280 by 1,024), file synchronization, PCMCIA configuration, and customization of your desktop.

Where's an outlet?
After several attempts, we found both systems can handle approximately 47 minutes of intense interaction on a single battery -- hardly long enough to let you keep working on a flight of any significance. RDI's battery pack -- a conglomeration of 6 NiCad D-size batteries shrink-wrapped together -- looks as if it came from a school science project. The only power management that RDI recommended -- which I found helpful, extending the battery life to 55 minutes -- was the lowering of screen brightness. Conversely, the SPARCbook 3's NCE software lets users control CPU clock speeds (20- to 50-MHz), disk spindown time-outs and inactivity shutdown times. After working with these options, we improved battery life to 70 minutes. Battery life is greatly influenced by the type of work you do and should be used only as a guide.

The battery pack of the SPARCbook 3 was significantly smaller and better-integrated then that of the PowerLite, allowing us to carry a spare in the carrying case, with a virtually unnoticeable addition of weight. The SPARCbook 3 LCD display indicates when the battery power is beginning to wane, but that is no reason to exit from an OpenWindows session. Once the power level hits the low battery threshold, the SPARCbook 3 writes its current memory configuration to a dedicated area of disk. Thus, upon battery change and power-up, the system returns to the exact state prior to the battery juggling. Changing the battery twice on a flight was inconvenient, but it allowed us to continue our work.

These ain't no SS20s
Performance is a truly relative measurement, and typically based on each user's individual frame of reference. If your personal system includes a SPARCstation 20 with 128 megabytes of RAM and a 19-inch Sony display, you'll likely be disappointed when moving to a travel-ready system. Nonetheless, these smaller systems are no slouches; they handle an average person's variety of applications and general Unix workloads.

Benchmarks can be misleading. Keeping in perspective that these mobile systems are designed as single-user systems, we measured the performance of the PowerLite and SPARCbook 3 using SPECint92, SPECfp92, and the Neal Nelson Business Benchmarks 2.4. Since both systems are based on TI's 50-MHz microSPARC, one would expect similar performance from both systems, but in fact there were several differences between the two.

Based on the SPEC ratings (26 SPECint92 and 21 SPECfp92) reported by both Tadpole and RDI, the two systems offer equal CPU performance. Unfortunately, the vendors did not provide complete microSPARC SPEC wrappers to the Advanced Systems Test Center (ASTC), and thus we were not able to run all of the SPEC benchmarks conclusively. Although preliminary SPEC tests hinted that our SPEC ratings may be several points lower than reported for both systems, numerous difficulties prompted us to omit the incomplete results from this review.

Graphics performance, as measured by x11perf (a series of x11 benchmarks), showed some differences -- with the SPARCbook 3 outmatching the PowerLite. (See the graph x11perf graphics performance for details. A comparison of current models' x11perf numbers to those of the older SPARCbook 2 (announced in 1993) shows significant improvement in mobile systems.

When we looked to other benchmarks, distinctions in performance became apparent. From the Neal Nelson tests, we determined the RDI system's performance showed an improvement of 5 to 30 percent over the SPARCbook 3 in the disk subsystem area and memory subsystem tests (see the sidebar Analyzing the Business Benchmark 2.4). Overall motherboard design is extremely important and could be a factor in the PowerLite's performance edge. The different operating systems and the second disk in the PowerLite also may have affected performance.

When all is said and done
The trade-offs between the two systems are slight. The PowerLite is more expandable and slightly faster and has a bigger, brighter, higher-resolution screen, but it is heavier and larger. The SPARCbook 3 is smaller and lighter, with a bit longer battery life. Either is a capable SPARC/Solaris portable for the mobile Unix professional.

About the author
Curt Aubley (curt.aubley@advanced.com) is a senior system engineer with Neal Nelson & Associates, and formerly evaluated the latest technology for the U.S. Army's Technology Integration Center.

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Analyzing the business benchmark

The Neal Nelson Business Benchmark 2.4 is a suite of 30 multitasking tests that isolate various computer subsystems. They are intended to highlight performance features and design trade-offs. We've illustrated the results of four of the more noteworthy tests (Test 1 highlights overall system performance; Test 10, 20, and 21 highlight subsystems) here as they relate to RDI's PowerLite and Tadpole's SPARCbook 3 computers. Because these systems are targeted for single users, we limited the benchmark load factor (number of copies) to 12. Note that due to time constraints, the tested systems configurations were not identical. Several performance differences between the two systems could be attributed to at least three areas: motherboard design, different operating system versions, and the addition of a second hard disk in the PowerLite.

Test 1 approximates the computer resource usage of an average office automation workload environment, stressing all of a computer's subsystems. Both systems show relatively good overall performance; the PowerLite exhibits a 10 percent performance advantage.

Test 10 profiles the size and speed of instruction, data, and/or combined memory caches, and main-memory access through various levels of increasing load. Initially, when the instruction and data areas are small and fit into the caching area, the PowerLite exhibits a slight performance advantage, which may be due to a superior motherboard design. Once the instruction and data areas surpass and defeat the cache areas, both systems show comparable performance.

Test 20 measures the throughput a computer earns reading a total of 40 megabytes of data sequentially as 5,120 records in 8-kilobyte blocks while Test 21 measures the corresponding writes. Test 20 is particularly interesting since the operating system version appears to make a notable difference in the performance of the sequential Unix file read results. Under lighter loads, the RDI's cache and memory architecture again shines with a slight advantage over the SPARCbook 3. After copy 6, the kernel cache on the PowerLite begins to be defeated and starts physical disk I/O. By utilizing Solaris 2.3's dynamic kernel buffering (and possibly better physical disk I/O), the SPARCbook 3 outperforms the Solaris 1-equipped PowerLite when handling larger work files. (We tested the PowerLite with the standard Solaris 1. Solaris 2.3 is available on request.

For Test 21, the PowerLite again exhibits a slight performance advantage under lighter loads of sequential writes, but continued increases in load appear to level out the playing field, with both systems exhibiting very similar performance under heavier loads.

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Why not use a PC-class notebook?

RISC-based portable systems such as these provide a good environment for Unix applications, but do you need so much expensive horsepower? Showing off that expensive nomadic machine might provide you with bragging rights among your co-workers, but if you are not putting the system to good use with power-hungry applications, it's just overkill. Scale your machinery to your work needs. If your on-the-road work centers around spreadsheets and word processing, contact managers, and e-mail -- in other words, if what you really need is a computerized notebook -- look first at the numerous general-purpose PC and Macintosh notebooks. Not only are they inexpensive, they have battery life measured in hours instead of minutes. How about Unix on Intel? That works, but depending on the Unix you choose and what you intend to do with it, you'll have to scale up that PC laptop's modest RAM and hard drive to the greater demands of an OS that's meant to kick some computing butt, not just read e-mail. So your savings won't be as great as it might first appear when reading those ads in the PC journals.

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Last updated: 1 February 1995.