---
title: "Types of array processing"
subject: "Computer Organization and Architecture"
chapter: 4
key: "semester_5/computer_organization_and_architecture:array-processing"
source: https://www.bctengineer.com/q/semester_5/computer_organization_and_architecture/array-processing
site: BCT Engineering
---

# Types of array processing

Computer Organization and Architecture · Chapter 4: Pipeline & Vector Processing

- Asked in: 2074 Asoj, 4 marks
- Video: [Array Processors In Computer Organization Architecture || SIMD](https://www.youtube.com/watch?v=5x99wpRtiNE) — Sudhakar Atchala
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/computer_organization_and_architecture/array-processing
- Whole chapter: https://www.bctengineer.com/md/semester_5/computer_organization_and_architecture/chapter-4

## Question

Describe the different types of array processing.

## Short answer

Attached array processor is an auxiliary processor connected via I/O, performing array computations with its own local memory. SIMD array processor has multiple processing elements controlled by one unit, all executing the same instruction on different data.

## Answer

An array processor is a processor that performs computations on large arrays of data. The term is used for two different types of processor.

#### 1. Attached array processor
An auxiliary processor attached to a general-purpose computer to improve its performance in numerical work. It connects to the host through an I/O interface and has its own local memory, which is linked to the main memory by a high-speed bus. The host computer does the general work, while the attached processor does array and matrix computations (for example, FFT and matrix multiplication) using multiple pipelined functional units.

```text
 General-purpose   I/O interface   Attached array
 computer  <--------------------> processor
     |                                 |
 Main memory <---- high speed memory bus ---> local memory
```

#### 2. SIMD array processor
A computer with many identical processing elements (PEs) under one control unit. Each PE has a local memory. The master control unit sends the same instruction to all PEs, and each works on its own data (Single Instruction, Multiple Data). Masking schemes can disable some PEs. An example is the ILLIAC IV with 64 PEs.

```text
        Master control unit
        /     |      |     \
     PE1     PE2    PE3 ... PEn
      |       |      |       |
     M1      M2     M3      Mn
```
SIMD array processors are good for vector and matrix operations; attached array processors improve an existing machine at a low cost.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What are the two types of array processor?
   A. Attached array processor and SIMD array processor
   B. SISD and MIMD array processor
   C. Linear and non-linear array processor
   D. Vector register and scalar array processor
   Answer: A. The answer describes attached array processors and SIMD array processors. (Key point: Types of array processor)

2. What is the role of an attached array processor?
   A. It replaces the host computer's main memory
   B. It is an auxiliary processor connected to a general-purpose computer to speed up numerical work like FFT and matrix multiplication
   C. It controls all I/O devices of the host
   D. It runs the operating system for the host
   Answer: B. It is attached through an I/O interface with its own local memory while the host does general work. (Key point: Attached array processor role)

3. In a SIMD array processor, how do the processing elements work?
   A. Each PE runs its own program on its own data
   B. The master control unit sends the same instruction to all PEs, each using its own local memory data
   C. PEs share one data item and execute different instructions
   D. Only one PE is active at a time
   Answer: B. SIMD means one instruction and multiple data; masking can disable some PEs. (Key point: SIMD array processor operation)

4. Which machine is the given example of a SIMD array processor?
   A. Cray-1 with 64 PEs
   B. ILLIAC IV with 64 PEs
   C. Pentium with 2 PEs
   D. ENIAC with 16 PEs
   Answer: B. The ILLIAC IV is quoted with 64 processing elements. (Key point: SIMD example)