3.2.9  Recent
          developments in           computer system
          architecture

Compare to a task like putting together a website: it is often more efficient to have a team of people all working on the same task. 

Much more detail for those interested can be found at, for example, at pages by John Morris of The University of Western Australia There you will find notes like these that you do not need for your studies but you may want to explore the topic via an extended essay.

On this page: [ processor architecture | primary memory | secondary memory ]

Processor Architecture

The architecture in which a single instruction is fetched into the CPU then decoded and executed is often called the von Neumann architecture after John von Neumann who first described it in a formal paper (see the history page for further details and links).  This can be restrictive (the von Neumann bottleneck).

Recent developments have included the single and multiple pipeline architectures.  In the single version an instruction can be fetched and another decoded while the first is still executing:

Each processor clock cycle, the instruction fetched moves on to be decoded, that decoded instruction is executed and a new one fetched. Under the von Neumann architecture the fetch, decode and execute of a single instruction each take one cycle.

In the multiple version pipelines work in parallel to increase the rate of processing of instructions still further.  These architectures, like cache memory, depend upon the fact that most programs have long sequences of sequential instructions (ie without branches). If there is a branch, the whole pipeline will have to be " flushed ".

A similar idea is to use multiple processors in parallel but in both these cases some additional co-ordination is needed in case one instruction depends upon the results of another executing at the same time or later on.

Supercomputers and mainframe computers make extensive use of multiple processors to share the workload.  In relatively recent developments such as Deep Blue and Cray supercomputers massively parallel architecture is employed.

The Cray site also has many examples of the applications this type of computer can be used in.

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Primary Memory

There is an excellent article on different types of RAM by David Risley hardware central, at:

http://www.hardwarecentral.com/hardwarecentral/tutorials/52/3/newLocation%3b

(or do a search if it has moved).

The point is always made about ROM that it cannot be written to except by a special machine (the blower).  An early development to allow testing of programs stored in ROM was the EPROM or Erasable Programmable ROM.  These chips can be recognized by a special window on top of the chip, shining UV light through this window will erase the chips contents and allow it to be re-programmed.

With the very rapid advances in modem and other technologies (scanners, CD-Writers, digital cameras), there was a need for a ROM that could be upgraded in the component itself and these newer devices are fitted with Flash ROM in which the program can be changed by downloading suitable software from a website.

Secondary Memory

We have mentioned ZIP discs and drives and CD-RW which are relatively new techniques for storing large (100MB - 3 GB) data on portable media.  There are a number of new storage media for portable devices like MP3 players and digital cameras. These include:

• Smart media
• Compact Flash
• Memory stick
• Multimedia Card

These media contain non-volatile memory, are typically small and have low power consumption.  They are ideal for use in small portable electronic devices which need to store data.  Typical sizes range up to 16GB on a card about twice the size of a standard postage stamp. Expect this figure to have increased by the time you read this. They are commonly used in digital cameras, media players and other portable devices.

A more interesting development has been the miniature mechanical hard drives such as the IBM Microdrive which has a capacity of 1 Gbyte and is about 2cm square and .5 cm thick. This drive can be used in portable devices, again including digital cameras. These devices have been superceded now that Flash memory has become so large and the price much reduced.

Data Communications

Increasingly available are two similar types of device.  The mobile phone which has data acquisition features for web browsing and email reading.  With the advent of WAP (Wireless Applications Protocol) this technology is expected to improve the amount of data that can be transferred to a mobile phone thus enabling portable web browsing, contact with company intranets and VPN's (Virtual Private Networks). 

The PDA (palm top or personal digital assistant) which is useful for storing contact information and can be synchronized with a pc.  Probably these two devices will converge so that you can carry your schedule and reminders with your telephone and, again, these can be linked to your company's network (and company databases) too.

Probably these have already converged if you are reading this more than 6 months after it was written.

These kind of technologies are supplemented by ever faster " backbones " (systems for transmitting data in networks, including the internet) and associated technologies such as ATM (asynchronous transmission) via cable modems (about 30 times faster than a 56 k modem).  

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related: [ Common core home | history page | previous: peripherals | next: operating systems ]

The main areas mentioned in the subject guide are:

• processor architecture
• primary memory technologies
• secondary memory

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