Architectures supported by Linux Kernel

Almost every processor architecture existing on Earth can support the Linux kernel, but only some of them are available directly inside the mainstream official sources as available from kernel.org.
If you download the latest tarball and you list the content of the "arch" subdirectory you'll find the following architecture names:
  • alpha
  • arm
  • avr32
  • blackfin
  • cris
  • frv
  • h8300
  • i386
  • ia64
  • m32r
  • m68k
  • m68knommu
  • mips
  • parisc
  • powerpc
  • ppc
  • s390
  • sh
  • sh64
  • sparc
  • sparc64
  • um
  • v850
  • x86_64
  • xtensa
They're even more than the ones supported by the GCC cross-compilers I was describing yesterday! It's simply because Julien does not package all the available ones but only the main ones.
The next step will be to calculate the intersection between the two lists, to see which are the preferred platforms to play with...


Why I love RISC

All the Laws of Nature are relatively simple: this is a reason why I used to love physics when I attended the Lyceum.
The greatness of simplicity and modularity applied to computers led me to love RISC architectures (for hardware) and UNIX systems (for software).
When I started learning the x86 Assembly language and I discovered that every instruction can belong from one to 17 (seventeen!) bytes I was shocked; there is an interesting comment about this written by Hennessy and Patterson in their books.

When studying RISC architectures the first ones encountered by the students are always MIPS (for its simplicity and orthogonality) and SPARC (for the idea of adding register windows to minimize accesses to memory); they are still my preferred ones.

To have an idea of which architectures are most widely used today you can have a look at the GCC cross-compilers maintained by Julien Lemoine on his site speedblue.org.
His page of the unstable packages for Debian reports the following architectures:
  • alpha
  • arm
  • hppa
  • ia64
  • m68k
  • mips
  • mipsel
  • powerpc
  • powerpc64
  • s390
  • sparc
  • sparc64
  • x86-64
As you can easily see, MIPS and SPARC have a great part here with 2 different targets each (MIPS is split by endianess and SPARC by register bit number).

Other important RISC architectures here being ARM and PowerPC.
For some reasons I do not like ARM cores:
  1. for a long period of time their cores have been an extension of the Intel monopoly under the names StrongARM and XScale (I have a PXA270 in my iPAQ);
  2. their strict IP protection policy made impossible for amateurs to access internals and to write their own HDL models (I remember a module named nnARM disappearing from OpenCores after developers received a letter from ARM lawyers);
  3. there are even too many implementation in current technological gadgets (this interesting article on EETimes explains that there could be up to 8 different ARM cores inside each Apple iPhones), and I love diversity as opposed to monopolies.
The last important RISC architecture is PowerPC (or POWER for IBM): after the switch of Apple Macs to use Intel micros their best implementation is in the Cell microprocessor of the Sony PlayStation 3 and in IBM POWER6 servers, while Motorola uses them in several embedded devices.
PowerPC cores could have changed the history of computers - but they didn't. So I'm always I bit sad when I have to talk about them.

The next step will be to see which architectures are actively supported by the Linux kernel.


And finally I bought the carputer

OK, so leave the news about the websites and start talking about real technology... I have a car with a double DIN slot (approx 18cm x 10cm) so I had the possibility to change the 8-years-old radio (compact cassette based) with a modern model. For a while I've been thinking a lot about building a Carputer by myself, using software and hints available from mp3car.com and motherboards with small form factors available from VIA or Intel.
But soon I realized that a model with all the characteristics I needed did not exist:
  • LCD touchscreen with 16:9 ratio and 7" wide;
  • ability to watch movies in DVD and DivX format and listen MP3 songs;
  • FM radio with RDS and TV tuner;
  • TomTom navigation software with maps of Europe on SD-Card.
Then I found the only model that supports it all: it is LF7100G from Linellae and if you want an idea of the price you can look at the CarDvdKit online shop. I've been following eBay auctions for a while and finally I won one for exactly 100 Euros less than the price you find on the online shop: the product will arrive in a few days and I hope that it is worth the 370 Euros I spent... I'll let you know!


Credits for the images

Sorry, I forgot to mention the authors of the images shown on my new home page.

The montage should have been done by my former colleagues Giuseppe Reitano, Massimo Spata and Gabriele Forzano (I did never know who had the major part in the work, so I'll say the three names). I'm not paying any royalties to them since the montage was their gift to convince me to leave the company...

Yesterday I copypasted their original Gladiator/Verificator montage into a frame I have bought on iStockphoto: for about 10 Euros I bought 10 credits and spent 2 of them for this frame designed by Peter Nguyen. I just rotated it to be exactly vertical.

Finally, the current corner of the page was taken from the mentioned Deziner Folio theme for WordPress that should have been designed by Navdeep Raj. His work is licensed under a Creative Commons Attribution 2.5 India License.

Thanks to everybody!


...and yet another very simple web site...

Yesterday I started this blog, and today to celebrate it I also renewed my personal web site at fazzino.it.
I removed a lot of old stuff that I do not want to share anymore (actually I did not remove the pages physically, but only the links, so you could still access them following Google's results).

I really wanted a very simple website, and to accomplish this task I created a site that now has only a single page with external links.

The new home page is very simple, and shows a white sheet on a black background. Since in the last days I've been studying a lot the blog software WordPress, I had access to several themes for it, and I found a very good "corner" in the Deziner Folio Theme 2.0 (it only has the bottom left corner, so I just had to rotate it several times with GIMP to obtain the 3 missing corners).

The center of the home page now shows a montage of the Gladiator promotional movie poster that my former colleagues at STMicroelectronics donated when I left the company on 2001-08-31. The face is mine, and they also substituted the writing "the Gladiator" with "il Verificatore" ("the Verifier" in Italian language). This happened because in ST I worked for some years in the field of Functional Verification. I still miss my colleagues.

Now that both the personal page and the web log are in place, in the next days I will be able to start writing about my interests: technology in general and especially processor architectures.


YAB - Yet Another Blog

Olé! Now I have a blog as well...
I was going to restyle my own site at fazzino.it and for a while I was thinking to install a blog software by myself, but for a series of reasons I had to change my mind.
After seeking for a while about freely available Blog Softwares, I chose WordPress, but then I realized that I did not have a working database server to access.
In fact:
  • Aruba.it, that hosts my website, offers MySQL databases for an additional fee, but I unsubscribed from this service when I renewed the hosting contract;
  • WordPress can be modified to run without MySQL dabases and using only a SQLite file, but the version of Apache installed on the hosts of Aruba.it only supports PHP4 without SQLite support;
  • I have access to other empty MySQL databases but they are hosted by GoDaddy and they can be accessed only from GoDaddy's network.
Then I tried some workarounds without success... and finally I decided to use an external blog, yet another free service available from the Big-G (I am already a full-time user of Gmail, Calendar, Analytics, iGoogle, Maps, Earth... and Android maybe next year).
I only have to say something about the URL of this blog... "simplyrisc" may refer to the company I work for, but it could also refer to the fact that the answer to many digital design problems is... simply RISC.
Keep in touch!