PC - RAM Memory (III)

SUMMARIZING

After reading the main features and parameters of RAM memory I have explained in the previous two posts, you are able to decide which RAM configuration you need for your personal computer.

But to summarize, here are my final recommendations for RAM memory purchases, which will remain valid even for the next generation platforms:

• I recommend to buy Kingston RAM memory modules.
  

• 2 modules of 1 GB or 2 modules of 2 GB of DDR2-800 or DDR2-1066 memory. It's not worth spending more money on DDR3 memory yet.
  

• Always get as few memory modules as possible, but equip all memory channels of a system to get maximum performance. The ideal configuration consists of two DIMMs today, and three DIMMs with Intel’s upcoming Core i7 systems.
  

• Look for quick timings, latencies for example (smaller numbers are better), but it's not worth spending substantial money on slightly faster modules.
  

• Spend additional budget on a faster processor, a faster graphics card or a faster drive instead of fast memory, unless you need overclocking memory

Read more »

PC - Memory DDR2 or DDR3?

What kind of memory: DDR2 or DDR3?


DDR3 advantages

One major factor favoring the purchase of DDR3 memory is that Intel is slowly moving all of its chipsets in that direction. Motherboard manufacturers expect big spenders to be the earliest adopters of new technology, so the majority of ultra-expensive motherboards will likely support only this latest memory standard while it gradually works its way into lower-cost markets.

DDR3 RAM memory module

While most PC builders won't "need" anything faster than mid-priced DDR2 for a while, DDR3 holds two key benefits over the technology it replaces: First, its maximum chip density has been extended to 8 Gb, allowing a 16-chip module to support a maximum 16 GB capacity. Second, its default voltage has been reduced to 1.50 volts from DDR2's 1.80 volts, resulting in a 30% power consumption decrease per clock speed.

However, the latest technology always comes at a significant penalty in value and DDR2 is more than sufficient for most systems, so why do we move to DDR3? Intel is likely preparing the desktop market for something big, specifically a move of the memory controller from the chipset to the CPU itself with its Intel i7 new processor. As with AMD's current products, this design eliminates the bandwidth limitations of a FSB and allows future processors to receive data as fast as it can be translated.

DDR2 and other RAM memory modules used currently

DDR3 drawbacks


It's often argued that DDR2 memory isn't fast enough for today's processors, as Intel's current fastest Front Side Bus (FSB) uses a 1333 MHz data rate. But this newer FSB doesn't require a "1333 MHz" memory to perform. As I explained in a previous post, Dual-Channel technology has stuck around so that today's FSB-1333 is easily fed by two DDR2-667 (PC2-5300) modules in dual-channel mode.


Another argument for buying DDR3 RAM memory could be for running memory "synchronously" to the CPU's FSB. But DDR3-1333 isn't synchronous to FSB-1333. Intel's FSB uses Quad Data Rate technology while the memory is only Double Data Rate. FSB-1333 runs at a 333 MHz clock rate, which is the same clock rate as DDR2-667.


Conclusion

So, in spite of DDR3 benefits, I think that it's not worth buying DDR3 memory yet. In my opinion, its benefits don't justify its price until new motherboards and processors compatible with DDR3 memory are cheaper and more developed (with a faster BUS for example). In the next post I will try to explain the key parameters I would take into account to decide which motherboard to buy

Read more »

PC - RAM Memory

After explaining a bit the microprocessor, here I will try to explain the key parameters I would consider to decide the RAM memory configuration for my Personal Computer:


Manufacturer

I strongly recommend to buy Kingston memory.


Number of modules

It's always advisable to minimize the number of memory modules. If we have four modules, for example, this may force the BIOS to work with relaxed timings and can cause memory compatibility issues and that the memory will work slower. The best choice is two modules to take advantage of dual channel.

Different RAM types. From top to bottom DIP, SIPP, SIMM 30 pin, SIMM 72 pin, DIMM (168-pin), DDR DIMM (184-pin).

Quantity of memory

Although 8 GB memory kits (which consist of four 2 GB DIMMs) are affordable, these only make sense if you have applications that really take advantage of the increased memory capacity. But these kits might give you the same headache as 3 GB kits, because all of them include four memory modules. This may force the BIOS to work with relaxed timings and can cause memory compatibility issues. A memory capacity of 2 GB is enough. If you think that you will need more memory, the best choice is to buy 2 modules of 2 GB each (a kit of 4 GB).

Dual Channel

Although Dual channel is a concept related to motherboards rather than memory, it's worth explaining here its importance. Dual channel can double the memory bandwith provided that the memory modules are completely identical.


Frequency

The more high is the frequency, the more fast the memory can work. But the frequency of the memory doesn't have to be much higher than the frequency of the bus. In this situation, the frequency of the bus is a bottleneck and the extra money we have spent on this memory will be wasted. It's extremely important to match the frequency of the RAM memory with the frequency of the bus.

For example, Intel's current fastest Front Side Bus (FSB) uses a 1333 MHz data rate. But this newer FSB doesn't require a "1333 MHz" memory to perform. Dual-Channel technology has stuck around so that today's FSB-1333 is easily fed by two DDR2-667 (PC2-5300) modules in dual-channel mode. In this example the RAM memory matches the frequency of the bus. Besides a DDR2-667 (PC2-5300)memory is synchronous to FSB-1333 because both runs at a 333 MHz clock rate.

So a DDR3-1333 memory isn't synchronous to FSB-1333 as Intel's FSB uses Quad Data Rate technology while the memory is only Double Data Rate. FSB-1333 runs at a 333 MHz clock rate, which is the same clock rate as DDR2-667.

Bandwith

The bandwith of a memory can be defined as:

Bandwith (Mbytes/seg) =Frequency of the memory (MHz) x 8 bytes

The easy method to convert data

rate to bandwidth is to multiply by eight. Thus, DDR-400 is called PC-3200; DDR2-800 is called PC2-6400 and DDR3-1600 is called PC2-12800.

The math behind this conversion factor is simple: PC memory modules based on SDRAM technology use a 64-bit connection; there are eight bits in a byte and 64 bits equal eight bytes. For example, DDR2-800 transfers 800 megabits per pathway per second; its 64 pathways provide one eight-byte transfer per cycle and 800 times eight is 6400. For example, today's faster memory is DDR3-1333 which has a peak bandwidth of 10666 MHz. This memory is commonly labeled as either PC3-10600 or PC3-10666.

Latency

RAM memory is structured in a table of rows and columns. The latency is the time elapsed, measured in clock cycles, between the request of reading a data and the moment in which this data is available. Values of latency are usually CL2'5, CL3, CL4, CL5.

Speed Vs. Latency

There's a myth that every new memory format brings with it a latency penalty. The myth is perpetuated by the method upon which latency labels are based: Clock cycles.

Consider the latency ratings of the three most recent memory formats: Upper-midrange DDR-333 was rated at CAS 2; similar-market DDR2-667 was rated at CAS 4 and today's middle DDR3-1333 is often rated at CAS 8. Most people would be shocked to learn that these vastly different rated timings result in the same actual response time, which is specifically 12 nanoseconds.

The problem perceived by many less-informed buyers is that faster memory responds more slowly, but it's obvious from these examples that this simply isn't often the case. The real problem isn't that response times are getting slower, but instead that they've failed to get quicker! When we see astronomical "speeds," we hope that our entire systems will become "more responsive" as a result. Yet, memory latencies are one place where things really haven't changed much. For example, with DDR400 and dual channel the theoretical bandwith would be 6400MB/s and with DDR2 800, the theoretical bandwith would reach 12800MB/s. But latencies can't be reduced, so the bandwith improves with DDR2 800 but only up tu 8GB/s more or less.

Conclusion

So I strongly recommend 2 identical Kingston modules of 1 GB each. If you needed more capacity, I would recommend 2 identical Kingston modules of 2 GB each. In the next post I will explain a bit the differences between DDR2 and DDR3 and whether it's worth choosing DDR3.

Read more »

PC - Microprocessor

The Microprocessor

Next you can find the main features of a microprocessor to be considered in order to choose the chip which matches better your needs.

Manufacturer

Currently there are two main manufacturers: Intel and AMD (Advanced Micro Devices). Intel processors were better until the appearance of the AMD Athlon in 2003. This AMD chip performs better than its competitor: Intel Pentium IV. But now Intel has recovered the leadership with his Intel Core 2 Duo. So there isn't a manufacturer absolutely better than the other one. For example, the better mainstream processor now is the Intel Core 2 Duo (two cores) or Intel Core 2 Quad (four cores).

AMD processors

But The Athlon 64 family had been superior to Intel's Pentium 4 or Pentium D offerings most of the time from the AMD64 launch in 2003 and Intel's introduction of the Core microarchitecture in 2006. While the Pentium 4 and Pentium D were aimed at reaching high clock speeds, their power requirements grew faster than the performance benefits.

As a consequence, AMD's approach of delivering more performance per clock was clearly more successful. Intel realized that a reasonable balance between processing cores and clock speed, based on the available manufacturing technologies, provides a much better path to more performance at reasonable power requirements. This eventually helped the company to get the crown back with Core 2 Duo.

Intel microprocessors

Technology

The main component of a microprocessor is the transistor. AMD phenom processor has more than 700 million of this semiconductor elements, most of them belonging to cache memory, so reducing the size of transistors the memory cache size can be increased. Nowadays Intel i7 processor technology is 45nm, where 45 nanometers is the length of a part of the transistor.

Architecture

When it's said that a processor has an architecture of 64 bits, then this processor can get 64 bits from the RAM memory simultaneously through the data bus. The more bits can get the processor simultaneously, the more fast can it work. Therefore a 64 bits processor with the suitable software can perform better than a 32 bits processor working at the same clock frequency. Another features concerning the architecture of a processor is whether it has memory cache and how much levels of this kind of memory it has,if it has also a memory controller included inside the processor and the number of cores it has.

Number of Cores

Until three years ago the microprocessors only had one core. The design and architecture of the chip was improved continuously (reducing voltage and transistors size and increasing memory cache size) so that the chip could work each time at a higher frequency and, this way, improve its performance.

But frequencies couldn't increase more without a big increase in power consumption and difficulties concerning power dissipation appeared (energy efficience). So manufacturers decided to decrease frequency of microprocessors and to use parallelism technology to keep improving perfomance of processors at lower frequencies. So manufacturers began to design chips with two o more processors inside, called cores.

AMD X2 3600 processor

Memory Cache. Layers

The microprocessor process the data obtained from the memory much faster than the time needed for the memory and the Bus to supply the next data. So the processor is often idle waiting for more data and its performance get worse.

For this reason a small but incredibly fast memory is put inside the microprocessor. This memory is called Cache and it normally contains the data the processor needs more often. This way the processor doesn't remain idle too much time. Even more than one level of memory cache are put in the processor to improve its performance.

The processors which don't have memory cache are also cheaper because the processor is easier to manufacture. For example, Intel sells Pentium processor with the tag Celeron. The processors called Celeron have much less memory cache, so they perform worse but are cheaper.

The main reason of the performance of the Core 2 Duo processor is its large and shared level 2 memory cache for both cores.

Frequency

The more high is the frequency, the more fast can work the processor. AMD processors always work at a lower frequency than Intel processors but some AMD chips can perform better because they can execute more instructions per clock cycle than Intel chips thanks to a more advanced architecture. Frequency is an important parameter to compare two processors provided they have a similar memory cache size and cores because a higher frequency can't compensate for a small memory cache. For example, a Pentium IV Celeron at 3.0 GHz performs worse than a Pentium IV 2.6 GHz.

Socket

In personal computers (PC), the microprocessor is inserted in a specific socket in a motherboard. The motherboard, through this socket, connects the microprocessor to the memory and to the peripherals. Through the peripherals, the processor can interact with the external world. Also in the motherboard some chips of RAM memory are inserted. The data between the RAM memory and the microprocessor is transferred by a bus, which is an electrical path between computer components.

Sockets Intel:

478 (Pentium IV and celeron)
LGA (Land Grid Array) 775 (from Pentium IV to Core 2 Duo)
Socket B (LGA 1366, incorporates the integrated memory controller and Intel QuickPath Interconnect)

Sockets AMD:

754 (Sempron i Athlon)
939 (Athlon 64 with dual channel)
AM2 (ATHLON 64 X2, supports DDR2 RAM memory)
AM3 (will support DDR3 RAM memory)

Read more »

PC - Introduction

With this post I start a serial with the main aim of explaining how a Personal Computer (PC) works and which are the most important features which have to be considered to buy a suitable PC for our needs.


Introduction

A computer is composed of several physical components, the hardware. The most important ones are the microprocessor, the memory and the motherboard (which controls the in/out devices and the memory and links them to the processor). The in/out devices are called peripherals. Examples of peripherals are the hard disk, the DVD unit, the graphic card, the sound card, the ethernet card, the modem and so on.

Elements of a current Personal Computer: Case, Screen, Keyboard and mouse

The microprocessor is the brain of the system and executes the instructions loaded in the memory, the software. This memory, called RAM (Random Access Memory), is really fast but can't store any information if the computer is off. On the other side, a hard disk is a massive memory (much more than the RAM but much slower) which can store the information indefinitely.

Computers only understand binary information. This language only has two symbols: o and 1, called bits. 0 means no electrical signal at all. 1 means some electrical signal. With eight bits we create a "word", called a byte. Each word represents a letter, a symbol or a number. So, when we type an 'a' with the keyboard, eight bits are generated, stored in the memory and sent to the processor. The amount of information a memory can store is precisely measured in bytes or Megabytes (a megabyte is a million of bytes).

There is a kind of software quite important: The Operating System (OS). The OS is loaded in the RAM memory when the computer is turned on. The OS has to manage the peripherals and tells the processor what to do every moment and where the data it need is.

The data needed by the processor is introduced through an IN device, like a keyboard, a mouse, a hard disk, a DVD unit. The results are shown in an out device, like a screen, a speaker...

The microprocessor, the RAM memory and the peripherals are all connected to the motherboard, and all of them are linked each other through a BUS. Through the data bus the information travels from one device to another one. The address bus is used by the processor to tell the memory where the next instruction or data it needs is stored.

An exploded view of a modern personal computer and peripherals:

1. Scanner, 2. CPU (Microprocessor), 3. Primary storage (RAM), 4. Expansion cards (graphics cards, etc), 5. Power supply, 6. Optical disc drive, 7. Secondary storage (Hard disk), 8. Motherboard, 9. Speakers, 10. Monitor, 11. System software, 12. Application software, 13. Keyboard, 14. Mouse, 15. External hard disk, 16. Printer

The components of a computer work syncronized by a clock. A clock tells each component when it has to send some information, when it has to get some information, when it has to process some information, when it has to show a result and so on. In short, the clock let the components talk and understand each other. A clock generates a lot of electrical impulses per second, and always the same number of impulses, so it has a frequency. The frequency is measured in Herz (Hz) or Megaherz (MHz). For example, if a clock generates a million of electrical impulses per second, it has a frequency of 1 MHz. The higher is the frequency, the faster the computer can work.

In the next post I will try to explain deeper the most important parts of a microprocessor and the features we have to consider to buy the processor more suitable for us.

Read more »

AEROSPACE TECHNOLOGY (III): SPACE AND COMMUNICATIONS

Communications Satellites


In 500 years, when humankind looks back at the dawn of space travel, Apollo's landing on the Moon in 1969 may be the only event remembered. At the same time, however, Lyndon B. Johnson, himself an avid promoter of the space program, felt that reconnaissance satellites alone justified every penny spent on space. Weather forecasting has undergone a revolution because of the availability of pictures from geostationary meteorological satellites--pictures we see every day on television. All of these are important aspects of the space age, but satellite communications has probably had more effect than any of the rest on the average person. Satellite communications is also the only truly commercial space technology- -generating billions of dollars annually in sales of products and services.


The Billion Dollar Technology


Perhaps the first person to carefully evaluate the various technical options in satellite communications and evaluate the financial prospects was John R. Pierce of AT&T's Bell Telephone Laboratories who, in a 1954 speech and 1955 article, elaborated the utility of a communications "mirror" in space, a medium-orbit "repeater" and a 24-hour-orbit "repeater." In comparing the communications capacity of a satellite, which he estimated at 1,000 simultaneous telephone calls, and the communications capacity of the first trans-atlantic telephone cable (TAT-1), which could carry 36 simultaneous telephone calls at a cost of 30-50 million dollars, Pierce wondered if a satellite would be worth a billion dollars.

After the 1957 launch of Sputnik I, many considered the benefits, profits, and prestige associated with satellite communications. By the middle of 1961, NASA had awarded a competitive contract to RCA to build a medium-orbit (4,000 miles high) active communication satellite (RELAY); AT&T was building its own medium-orbit satellite (TELSTAR) which NASA would launch on a cost-reimbursable basis; and NASA had awarded a sole- source contract to Hughes Aircraft Company to build a 24-hour (20,000 mile high) satellite (SYNCOM).

Sputnik satellite, the first Satellite launched into space

By 1964, two TELSTARs, two RELAYs, and two SYNCOMs had operated successfully in space. This timing was fortunate because the Communications Satellite Corporation (COMSAT), formed as a result of the Communications Satellite Act of 1962, was in the process of contracting for their first satellite. On April 6, 1965 COMSAT's first satellite, EARLY BIRD, was launched from Cape Canaveral. Global satellite communications had begun.


The Global Village: International Communications


Some glimpses of the Global Village had already been provided during experiments with TELSTAR, RELAY, and SYNCOM. These had included televising parts of the 1964 Tokyo Olympics. Although COMSAT and the initial launch vehicles and satellites were American, other countries had been involved from the beginning. AT&T had initially negotiated with its European telephone cable "partners" to build earth stations for TELSTAR experimentation. Further negotiations in 1963 and 1964 resulted in a new international organization, which would ultimately assume ownership of the satellites and responsibility for management of the global system. On August 20, 1964, agreements were signed which created the International Telecommunications Satellite Organization (INTELSAT).

Three Crew Members Capture Intelsat VI

By the end of 1965, EARLY BIRD had provided 150 telephone "half- circuits" and 80 hours of television service. The INTELSAT II series was a slightly more capable and longer-lived version of EARLY BIRD. The INTELSAT III series was the first to provide Indian Ocean coverage to complete the global network. This coverage was completed just days before one half billion people watched APOLLO 11 land on the moon on July 20, 1969.

From a few hundred telephone circuits and a handful of members in 1965, INTELSAT has grown to a present-day system with more members than the United Nations and the capability of providing hudreds of thousands of telephone circuits. Cost to carriers per circuit has gone from almost $100,000 to a few thousand dollars. Cost to consumers has gone from over $10 per minute to less than $1 per minute. If the effects of inflation are included, this is a tremendous decrease! INTELSAT provides services to the entire globe, not just the industrialized nations.


New Technology


In the early 1960s, converted intercontinental ballistic missiles (ICBMs) and intermediate range ballistic missiles (IRBMs) were used as launch vehicles. These all had a common problem: they were designed to deliver an object to the earth's surface, not to place an object in orbit. Upper stages had to be designed to provide a delta-Vee (velocity change) at apogee to circularize the orbit. The DELTA launch vehicles, which placed all of the early communications satellites in orbit, were THOR IRBMs that used the VANGUARD upper stage to provide this delta-Vee. It was recognized that the DELTA was relatively small and a project to develop CENTAUR, a high-energy upper stage for the ATLAS ICBM, was begun. ATLAS-CENTAUR became reliable in 1968 and the fourth generation of INTELSAT satellites used this launch vehicle.

Atlas Centaur rocket launch. A rocket like this one launched the satellite Intelsat IV

The fifth generation used ATLAS-CENTAUR and a new launch-vehicle, the European ARIANE. Since that time other entries, including the Russian PROTON launch vehicle and the Chinese LONG MARCH have entered the market. All are capable of launching satellites almost thirty times the weight of EARLY BIRD.

Ariane V lift-off

In the mid-1970s several satellites were built using three-axis stabilization. They were more complex than the spinners, but they provided more despun surface to mount antennas and they made it possible to deploy very large solar arrays. The greater the mass and power, the greater the advantage of three-axis stabilization appears to be. Perhaps the surest indication of the success of this form of stabilization was the switch of Hughes, closely identified with spinning satellites, to this form of stabilization in the early 1990s.

Much of the technology for communications satellites existed in 1960, but would be improved with time. The basic communications component of the satellite was thr traveling-wave-tube (TWT). These early tubes had power outputs as low as 1 watt. Higher- power (50-300 watts) TWTs are available today for standard satellite services and for direct-broadcast applications. An even more important improvement was the use of high-gain antennas. Focusing the energy from a 1-watt transmitter on the surface of the earth is equivalent to having a 100-watt transmitter radiating in all directions. Focusing this energy on the Eastern U.S. is like having a 1000-watt transmitter radiating in all directions. The principal effect of this increase in actual and effective power is that earth stations are no longer 100-foot dish reflectors with cryogenically-cooled maser amplifiers costing as much as $10 million (1960 dollars) to build. Antennas for normal satellite services are typically 15-foot dish reflectors costing $30,000 (1990 dollars). Direct-broadcast antennas will be only a foot in diameter and cost a few hundred dollars.


Mobile Services


In February of 1976 COMSAT launched a new kind of satellite, MARISAT, to provide mobile services to the United States Navy and other maritime customers. In the early 1980s the Europeans launched the MARECS series to provide the same services. In 1979 the UN International Maritime Organization sponsored the establishment of the International Maritime Satellite Organization (INMARSAT) in a manner similar to INTELSAT. INMARSAT initially leased the MARISAT and MARECS satellite transponders, but in October of 1990 it launched the first of its own satellites, INMARSAT II F-1. The third generation, INMARSAT III, has already been launched.

An aeronautical satellite was proposed in the mid-1970s. A contract was awarded to General Electric to build the satellite, but it was canceled--INMARSAT now provides this service. Although INMARSAT was initially conceived as a method of providing telephone service and traffic-monitoring services on ships at sea, it has provided much more. The journalist with a briefcase phone has been ubiquitous for some time, but the Gulf War brought this technology to the public eye.

The United States and Canada discussed a North American Mobile Satellite for some time. In the next year the first MSAT satellite, in which AMSC (U.S.) and TMI (Canada) cooperate, will be launched providing mobile telephone service via satellite to all of North America.


Competition


In 1965, when EARLY BIRD was launched, the satellite provided almost 10 times the capacity of the submarine telephone cables for almost 1/10th the price. This price-differential was maintained until the laying of TAT-8 in the late 1980s. TAT-8 was the first fiber-optic cable laid across the Atlantic. Satellites are still competitive with cable for point-to-point communications, but the future advantage may lie with fiber-optic cable. Satellites still maintain two advantages over cable: they are more reliable and they can be used point-to-multi-point (broadcasting).

Cellular telphone systems have risen as challenges to all other types of telephony. It is possible to place a cellular system in a developing country at a very reasonable price. Long-distance calls require some other technology, but this can be either satellites or fiber-optic cable.


The LEO Systems


Cellular telephony has brought us a new technological "system"-- the personal communications system (PCS). In the fully developed PCS, the individual would carry his telephone with him. This telephone could be used for voice or data and would be usable anywhere. Several companies have committed themselves to providing a version of this system using satellites in low earth orbits (LEO).

The most ambitious of these LEO systems was Iridium, sponsored by Motorola. Iridium planned to launch 66 satellite into polar orbit at altitudes of about 400 miles. Each of six orbital planes, separated by 30 degrees around the equator, would contain eleven satellites. Iridium originally planned to have 77 satellites-- hence its name.


Prospect and Retrospect


Arthur C. Clarke's 1945 vision was of a system of three "manned" satellites located over the major land masses of the earth and providing direct-broadcase television. The inherent "broadcast" nature of satellite communications has made direct-broadcast a recurrent theme--yet one never brought to fruition. The problems are not technical--they are political, social, and artistic. What will people be willing to pay for? This is the question-- especially with the availability of 120-channel cable systems. Hughes is apparently about to enter this field and may encourage others to do the same. Only then will Clarke's prophetic vision be fulfilled.

There are currently six companies providing fixed satellite service to the U.S.: GE Americom, Alascom, AT&T, COMSAT, GTE, and Hughes Communications. They operate 36 satellites with a net worth of over four billion dollars. Each year from 10-20 communications satellites are launched valued at about $75 million each. The launch vehicles placing them in orbit have similar values. Both satellites and launch vehicles are multi-billion dollar businesses. The earth station business is equally large. Finally the communications services themselves are multi-billion dollar businesses. John R. Pierce was right--it would be worth a billion dollars.



A Selective Communications Satellite Chronology


* 1945 Arthur C. Clarke Article: "Extra-Terrestrial Relays"
* 1955 John R. Pierce Article: "Orbital Radio Relays"
* 1956 First Trans-Atlantic Telephone Cable: TAT-1
* 1957 Sputnik: Russia launches the first earth satellite.
* 1960 1st Successful DELTA Launch Vehicle
* 1960 AT&T applies to FCC for experimental satellite communications license
* 1961 Formal start of TELSTAR, RELAY, and SYNCOM Programs
* 1962 TELSTAR and RELAY launched
* 1962 Communications Satellite Act (U.S.)
* 1963 SYNCOM launched
* 1964 INTELSAT formed
* 1965 COMSAT's EARLY BIRD: 1st commercial communications satellite
* 1969 INTELSAT-III series provides global coverage
* 1972 ANIK: 1st Domestic Communications Satellite (Canada)
* 1974 WESTAR: 1st U.S. Domestic Communications Satellite
* 1975 INTELSAT-IVA: 1st use of dual-polarization
* 1975 RCA SATCOM: 1st operational body-stabilized comm. satellite
* 1976 MARISAT: 1st mobile communications satellite
* 1976 PALAPA: 3rd country (Indonesia) to launch domestic comm. satellite
* 1979 INMARSAT formed.
* 1988 TAT-8: 1st Fiber-Optic Trans-Atlantic telephone cable

This post is an extract from: Communications Satellites: Making the Global Village Possible by David J. Whalen

Read more »

LARGE HADRON COLLIDER

Today has begun the experiment called Large Hadron Collider (LHC). This experiment is located in CERN (European Organization for Nuclear Research) and is considered the scientific experiment of this century. It has costed 3000 millions euros and, in order to build it, more than 10000 scientists have taken part. This experiment has been built in a circular tunnel 27km long in the border between France and Switzerland depths, at between 50 and 120 meters under the floor.

LHC architecture and its experiments

The LHC is really an enormous particle accelerator which constitutes the most powerful machine ever built by physicians. This accelerator will make possible collisions of high energy protons at almost the speed of light. The main goal of this high energy collisions is to discover the hypothetical Higgs boson, which is predicted by the Standard Model of elemental particles.

These are the four main experiments in the LHC:

- CMS (the Compact Muon Solenoid) - and Atlas are the LHC's general purpose detectors to investigate a wide range of physics, including the search for the elusive Higgs boson, extra dimensions, and particles that could make up dark matter, which gives other particles their mass. Atlas will be responsible for the search of dark matter.

CMS detector for LHC

- The LHC Beauty (LHCb) detector is designed to answer a specific question: where did all the anti-matter go? Equal amounts of matter and its opposite counterpart anti-matter were created in the Big Bang. But today we find no evidence of, for example, anti-matter galaxies or stars. The LHCb experiment will help us to understand why we live in a Universe that appears to be composed almost entirely of matter, but no antimatter.

- ALICE While the other LHC detectors will use proton beams to do their science, Alice relies on smashing together electrically charged lead atoms. Scientists hope to re-create a state of matter called quark-gluon plasma which existed just after the Big Bang.Matter was in this "liquid" state because the early Universe was still extremely hot.The Alice detector will be used to study this quark-gluon plasma as it expands and cools. In doing so, they will observe how it progressively gives rise to the particles that make up the matter in our Universe today.

Concerning the LHC there are some scientists who are afraid the LHC could cause the end of the world. Experts deny that dangerous black holes could be generated in the LHC. The LHC, like other particle accelerators, recreates the natural phenomena of cosmic rays under controlled laboratory conditions. As this natural phenomena has been happening for millions of years and the Earth still exists, there is no reason, as I see it, to be worried about it.

To know more:

http://news.bbc.co.uk/2/hi/science/nature/7534847.stm

http://public.web.cern.ch/public/en/LHC/LHC-en.html

http://public.web.cern.ch/public/en/LHC/Safety-en.html

Read more »