Parallel ATA, Serial ATA, SCSI under Linux .. basics

It’s not possible to go through device management in Linux without saying a word about ATA (Advanced Technology Attachement) and SCSI (Small Computer System Interface) buses…. and of course about USB, but not in this post.

So … ATA, which is an interface standard for connecting storage devices and has been invented by IBM. But its derivate, widely known in the world of x86, is PATA (Parallel ATA) whose first version developped by Western Digital and named IDE (Integrated Drive Electronics), also a very popular acronym.

Which were its characteristics, or better said which were its drawbacks and why currently is only history?

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Device management in Linux … continued

In case you read my previous post about the intricacies of /proc directory, now I would like to continue in the same line and tell my thoughts about other two Linux folders being mount points for virtual filesystems, /dev and /sys. 

Before going further I just want to share with you an interesting resource that I found about this extended topic how Linux sees PnP devices) which outlines probably better what I am trying  to do in a couple of posts :) (very useful and intuitive the CPU privilege rings, also the communication diagram at the end)

What to say about /sys, or about Sysfs (file system)? Since I am a very “young” Linux user I do not have the practical understanding and meaning of it… I just can add my impression to the dozens of the  already existing ones on forums, discussion lists, or simply … on Google …

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What to start with? (/proc directory)

The very first part to start with is the System architecture chapter from LPIC-1 exam 101. Here you may find a pretty well documented tutorial from IBM, which is also referred as an “approved training material” on the official LPI site. What’s in there?

Besides trivial things like how you hould enter a BIOS menu, how to play in BIOS menus (take a lot of care here, since it may have serious consequences), what is POST, how to configure BIOS to boot without a keyboard, what is a hotplug and coldplug device … I would start tackle this first tutorial discussing about the mysterious /proc, /dev and /sys folders, of course there are more interesting things in here, like SCSI drivers, how Linux sees and treats SCSI devices, also about USB drivers, but probably in an upcoming post.

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Get a grip on LPIC 1

Ok, if you decided to go for this cert what’s needed in order to prepare it?  What training materials are available on the market and what are the requirements (or objectives) of this training?

Here you may find an extended answer to all your doubts simply expressed by myself in the 2 questions above. Personally I would recommend this one as one of the best resources to use in preparing for LPIC. Nevertheless you should always bear in mind the objectives of the exam.

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Does it worth to have a Linux certification?

I would say so … Anyhow Linux is so spread in our everyday programmers/engineerings’ life that is really difficult to find someone having no idea about it (in fact I would say is a shame as an engineer NOT to get a grip on Linux). But, is it required, or do you think is needed, to have a Linux certification?

As far as I knew since long time ago there was the “notorious” Red Hat certification-  RHCE which once was a de facto requirement for a senior system admin aspiring to get into one of the top IT companies. LPIC (Linux professional institute certification) is a much younger certification, its governing entity, Linux Professional Institute, being established in 1999. Despite RHCE, LPIC is not tied to any Linux distribution or Linux vendor, and as the name suggest is provided by a non-commercial organization.

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Hands on FPGA power optimization techniques

Well … enough with introductory talk, let’s have an eye on some power estimation and optimization techniques on FPGAs.

Some important things to have in mind from previous post :

1. Statical power is power consummed when there is no logic activity and is dued to physical nature of silicon devices (90nM, 65nM technology …)

2. Dynamic power consumption comes from logic activity (toggle rate) and may have some components, one of them is short circuit power, another is dued to glitches (unwanted logic states that may appear because of unequal switching times of the inputs)

Obviously the largest between the two is the dynamical one, which depends on capapcitance, supply voltage and frequency of operation as in the relation below:

Is it really difficult to estimate and then to reduce the dynamic power consumption on an FPGA?

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What is statical and dynamical power consumption?

Well, the idea of this post was somehow to introduce a further discussion about intricacies of power management and calculations how to handle all this in FPGAs context.

Basically the difference between the two resides in the state of the transistors that the corresponding IC is made of. Dynamic power consumption refers to power consumed when logic states of transistors are switching, static power refers to power consumed while transistors are in idle state or in other words is the “leakage power”.

So dynamic power dissipation can come from logic activity, whenever the chip is not in standby or in sleep, this is what we also name transient power. I will not go through complicated calculations, since me neither I do not understand them, but I will simply come and saying that this kind of power dissipation strongly depends on supply voltage and clock frequency used

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