25.2. Horizontal Micro Program

So, this is just again very quickly very quickly let us look at now we are going to take a more elaborate depth with more clear examples that, optimization is done on the signals by encoding. So, last unit we have already dis discussed that encoding is very important.

This chunk introduces the concept of micro programs and the role of encoding in optimizing signals. The speaker indicates that this section will delve deeper into examples of how signals can be encoded to improve performance.

Think of encoding as a way to simplify communication. Just as using abbreviations (like 'LOL' for 'laugh out loud') helps convey messages faster, encoding signals helps the computer process instructions more efficiently.

If there are n control signals in the CPU, the length of each control word of the memory will be n very simple there is a horizontal micro program everything is parallel.

This chunk explains that in a horizontal micro program, the CPU uses 'n' control signals, and each control word has a length of 'n'. This means that the system can handle multiple operations simultaneously, leading to faster processing times.

Imagine a multi-lane highway where each lane represents a control signal. Just as multiple cars can travel in different lanes simultaneously, allowing traffic to flow faster, horizontal micro programs allow the CPU to process several signals at once.

To do this we have seen that in the last unit, that we have to optimize by encoding the signals, which is actually called the vertical micro instruction.

This section states that to optimize the control signals, encoding the signals is necessary. This process creates vertical micro instructions, which compress the amount of data needed, making the memory usage more efficient.

Consider packing a suitcase for a trip. You can either throw clothes in haphazardly (which is inefficient) or roll them tightly to save space (which is efficient). Encoding signals is like rolling the clothes tightly so that less space is used in memory.

But in this case only one bit signal can be made a 1. So, if simultaneously 3 or 4 points to be a 1 you require 4 cycles for that.

The drawback of using a fully compressed vertical micro program is that it allows only one signal to be activated at a time. Hence, if multiple signals need to be activated together, it takes longer, slowing down the performance.

Imagine trying to fit multiple items in a single box. If you can only take one item out at a time, you’ll spend more time retrieving everything, which is like having to wait for cycles before the next signal can be activated.

So, what we basically do is that, we go for basically something called a hybrid approach in hybrid we make clustering and for each clustering we will try to put signals in one cluster, which need not be 1 simultaneously.

The hybrid approach introduces clustering, where signals that do not require simultaneous activation are grouped together. This method aims to utilize both parallel processing and the compression benefits of encoding while minimizing latency.

Think of teams working on different projects. If some groups can work independently without waiting for others, the overall progress is faster, similar to how clustering allows non-simultaneously activated signals to be efficiently managed.

So, we are taking a single bus architecture, now we will mainly focusing on example because theory mainly we have covered in the last unit.

The section shifts focus to a practical example of a single bus architecture, which serves as a case study for the concepts discussed. It underscores the importance of applying theoretical knowledge to real-world systems.

Imagine reading a recipe where the theory of cooking is explained, but now it's time to cook a specific dish. The single bus architecture serves as that 'dish' where students apply what they've learned about encoding and clustering.

So, let us count how many input and output ports are there. So, 1 2 there are 7; 4 user registers, 3 system registers 7 into 2 14 then 15 16 17 18 19 20 21 22, 23 I miss something 1, 2, 3, 4, 5 6, 7 8, 9, 10 sorry 10; 10 over here, and 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22 20 actually there are 24 signals will be there you just count.

This chunk emphasizes the importance of counting control and data signals in a single bus architecture. The counting reveals how many ports are necessary for input and output, affecting overall design and efficiency.

Think of a water supply system where you need to know how many faucets (output ports) and pipes (inputs) are present to ensure that enough water reaches each outlet without running dry or overflowing.

So, this will obviously lead to lower bit space utilization, which is the case in horizontal micro program.

The issues with horizontal micro programs include inefficiencies due to lower usage of bits, resulting from the fact that many signals often remain unused in given configurations, leading to wasted memory.

Imagine a party with a long buffet table where only a few dishes are eaten and others go untouched. Just as some items may end up wasted due to lack of demand, so too can memory space go to waste with underutilized signals.

So, if you take all the counts and put in the flat architecture the size will be very high already we have discussed so many times, which will be a horizontal micro program.

This part concludes that by using clustering in hybrid micro programs, one can significantly reduce the memory size needed for controlling signals while maintaining speed efficiency, contrasting sharply with flat architectures.

Consider organizing books on a shelf. If they are grouped by categories (hybrid approach), it takes up less space and is much easier to find a book, instead of scattering books randomly on the floor (horizontal approach).

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