Product Review: Siemens' SIMpad SL4

If it looks like a duck and it quacks like a duck, then the SIMpad is a tablet PC.

Product: SIMpad SL4Manufacturer: SiemensURL: less than $400

Siemens is known to the public mostly for the cellular phones it builds. But Siemens has other interesting hardware that one should discover--like the SIMpad SL4.

Apple-Like Design

The SIMpad SL4 is a beautiful machine. A sleek and polished look is an important feature for such machines, which may be used on the go. It also feels solid and is easy to use with only one hand. The big buttons are placed conveniently on only one side of the screen.

Measuring 10.35 x 7.08 x 1.10 inches, this piece of hardware is incredibly light--only 2.2 lbs.. Forget your heavy laptop; only my Sony C1V Picturebook is as light. All of this makes the SIMpad an excellent companion for long work days, where every ounce matters.

Another interesting feature is the LiIon battery life, up to seven hours according to Siemens. But my tests with a PCMCIA 802.11b Wi-Fi card lasted nearly seven hours, which means the SIMpad without any PCMCIA card may last longer. Now you can really leave the AC adapter at home.

A Grown Up Zaurus 5500

Powered by a 206MHz StrongARM processor, featuring 64MB of RAM and 32MB of Flash memory, a microphone, a speaker, a serial port, an infrared port, a smart card port, a PCMCIA port and a USB slave port, the SIMpad SL4 looks like a grown up Zaurus 5500. Only two details are different--the SL4 has a beautiful 800x600 TFT touch screen, with 65,000 colors supported. While not as bright and crisp as the Sharp Zaurus C700 screen, the SL4 can be used perfectly outdoors.

The other difference between the Zaurus and the SIMpad is the missing keyboard. The SIMpad is not a PDA or a laptop but a tablet PC, and tablet PCs do not have keyboards. Too bad; even a small 5500 keyboard would have been welcome, say, below the screen. You can, however, purchase a serial keyboard, such as the iBiz serial keyboard, which is reported to work with the SIMpad. It connects to the sync cable, but iBiz was not able to provide me such a keyboard for tests.

Perhaps the tablet PC label should be discussed here. Some say only i386 hardware capable of running Windows XP and featuring a touchscreen which cannot be activated by fingers or other objects truly can be called tablet PCs. I think this is far too restrictive; i386/XP requirements are due to the heavy usage of not free operating systems coming from Redmond. In fact, the SIMpad can and does run Linux. As with an iPAQ, you can remove Windows CE to use a handheld distribution, including OPIE or GPE. You also can run standard Linux applications if you have a PCMCIA hard disk on which to store them all and if you can find ARM binaries. But many distributions now release ARM packages, and you can cross-compile from your PC any missing application you may need.

Personally, being unable to use my fingers on the touchscreen is not a feature but a bug. I want to be able to click on the screen with anything I have nearby, like a closed pen. Restricting the use of the touchscreen to fingertips sounds like a bad idea to me.

The First Linux Tablet PC

Initially announced in January 2001 at CES, the SIMpad SL4 was not immediately on the market. An initial $1,500 price tag, when the first Windows XP tablet PC were announced, meant the SL4 was not a big seller in the mainstream market. Now it can be found in Germany and Switzerland for much less, as little as Eur. 199 for the Windows CE version (called Sinus Pad) and Eur. 385 for the Linux flashable version (SIMpad SL4). The SIMpad SLC, an SL4 with DECT cordless phone support, is sparingly available. If you have a DECT compatible cordless phone, go for it because you will not need Wi-Fi. Otherwise, forget the SLC because of possible collisions on the unlicensed 2.4GHz band.

An SL4 itself still can be hard to track down. Be prepared to read and write German (or use Babelfish) if you want to get one. I was able to purchase one from NRG Systems, an Augsburg-based company operating mostly on The service was excellent, and I received my SIMpad by COD in only a few days.

The first thing I did was flash a Linux image from; I recommend image-opie_0.9.1 to get a Zaurus-like OPIE environment. OPIE support is being actively developed by Chris Martin, who also helped me with OPIE support.

Figure 1. The very same Qtopia user interface from the Zaurus is available on the SIMpad in its free software version called OPIE.



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problem to start working with SIMPAD SL4

mehrdad Khansary Atigh's picture

Dear Sirs,
I have purchased simpad sl4 recently and have problem to calibrate its display.I perform the instructions according to operation manual of simpad sl4 but after calibration the message of " please press Enter to save calibration" appears, but no keyboard menu or Enter can be found on the display.So kindly help me how I can calibrate it.

By the way , please inform me how I can connect a flash memory to the simpad sl4 .there is not installed any port on it.

I will be waiting for your prompt reply.

Best Regards
Mehrdad Khansari Atigh

Re: Product Review: Siemans' SIMpad SL4

Anonymous's picture

Nothing strange at all. OpenSIMpad [] brings new life to the device!

Michael Lauer
OpenSIMpad core developer

Re: Product Review: Siemans' SIMpad SL4

Anonymous's picture

Fantastic! After reading this article I recalled that Swisscom, a major ISP & phone company here in Switzerland, had briefly carried the Simpad in their retail stores. Killing time I walked into one yesterday to enquire about it, expecting the answer to be, "what are you talking about?". To my surprise the store had two units in the back that were returned and apparently Siemens didn't want them back. They reluctantly sold it to me for 300 CHF (230.749 USD). Wow, if you guys do not own one you are missing out. Most of the problems the artice above highlighted have been addressed. I use it for on the road PHP Dev and surfing at home. Thing is surprisingly fast for 206 mhz and the screen is bright and perky. If anyone would like to have one drop me an email at and I'll see what I can do for you. Linux rules!

Re: Product Review: Siemans' SIMpad SL4

Anonymous's picture

You can buy this SIMpad SL4 at:
One of the Siemens Dealers in the Netherlands

Re: Product Review: Siemans' SIMpad SL4

Anonymous's picture

This product is End-Of-Life, so it's a bit strange that the review
is appearing on this site....

Siemens Dealership
The Netherlands