Posts Tagged ‘microprocessors’

Segementing how a microprocessor manages more than 64K of memory

April 25, 2013

Segmenting is a memory management technique which microprocessors use to address more than 64kilobytes memory.In this example I will demonstrate how
Intel 8086 accomplishes addressing more than 65K memory.

A memory word is addressed by addressing by  adding a segment pointer and a word address as shown
in the picture.

The possibility of addressing one megabyte doesn’t necessary mean that the processor has a physical memory of 1MB.
You can make a program as if the processor had 1MB of memory and the
processor can fetch the segment that is being addressed from the computers hard drive.


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Writen by: Rikard Grossman-Nielsen
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How microprocessors handle interrupts:interrupt management

July 31, 2012

Intetrrupts are made asynchronously to the main code which is executed whereas polling is performed syncronously to the application being executed. The main advantage of interrupts are that they give a short reponse time if we assume that several interrupts are not made at the same time. In realtime systems which must respond to events very fast interrupts must be used to achieve a quick enoguh response.

The three disadvantages of interrupts are:

1. They require extra hardware, especially if interrupt management is to be done outside the processor.
2. Each time an interrupt is made, a time is needed to handle the interrupt. This ammount of time is called overhead.
3. The interrupt routine is exected aschynorously to the the main thread which means that it’s diffciult to know how much memeory that needs to be allocted for interrupt management.

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Writen by: Rikard Grossman-Nielsen,
ITService-GNR (ITTjänst-GNR),
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Intel 8080 and the way the 40pins limits it’s IO performance.

February 23, 2012

Another lesson on microprocessors and the intel8080 especially. The Intel 8080 has 40pins which enables it communicate with the outside world. The processors is 16bit bits internally but it only has enough pins on the databuss to fetch 8bits at a time. The processor is able to process 16bit instructions by fetching two 8bit memory positions after each other through use of a technology called multiplexing. The problem is that the multiplexing technology is slow so at best the intel 8080 is only a little bit faster than an 8bit processor of similar specifications. The only way of speeding up the Intel 8080 and making it able to load 16bits at a time from memory would be to give it more pins to communicate with the outside world.

A nice video on microprocessors

February 18, 2012

I found a nice video from Intel on how microprocessors are manufactured. The video describes the manufacturing process of a microprocessor in laymen terms.
Click this link to see the video.

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It is an interesting fact that microprocessor of different architecture perform roughly the same.

February 8, 2012

I’ve read some more on how 8080 process JMP instructions. I’ve also read a comparsion on the architecture of motorola 6800, z80 and in8080. The 6800 has a few number of registers compared to z80 and intel8080 which have a similar number of registers. It is an interesting fact that these microprocessors have roughly the same performance but with different designs. You should also note that roughly the same speed is meant as an average and thah some of these might perfom better than the other hen it comes to certain operations.

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