01 02 Overview of Computer System Structure — Transcript

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1. 0:08[Music]
2. 0:21overview
3. 0:23of a computer system structure
4. 0:27computer system
5. 0:28organization so what are all the parts
6. 0:32and how they
7. 0:33fit together
8. 0:34okay
9. 0:35so computer system operation
10. 0:38so one or more cpus device controllers
11. 0:41connector common bus
12. 0:43providing access to shared memory
13. 0:45so concurrent execution of cpus and
14. 0:48devices
15. 0:49competing for the memory cycles
16. 0:52so basically
17. 0:54all the
18. 0:56components or peripherals or devices
19. 0:58connected to computer systems house
20. 1:00watch called controllers
21. 1:02these controllers communicates with the
22. 1:05cpu via the operating systems
23. 1:08okay so we provide device drivers for
24. 1:12the controller
25. 1:13so if the user want to communicate with
26. 1:15the hardware
27. 1:17okay it will be possible via this
28. 1:20controller communicating with the
29. 1:21operating systems and then really
30. 1:23hardware
31. 1:24okay so all devices and peripherals in
32. 1:27the computer system has their own
33. 1:30controllers
34. 1:31just like on this diagram here you've
35. 1:33got this controller for the disks you've
36. 1:36got usb controller if you are using the
37. 1:38usb mouse keyboard and printer and other
38. 1:41devices
39. 1:42okay
40. 1:43so your graphic card also has an adapter
41. 1:48okay and all of this are using
42. 1:51a system bus or a common system bus
43. 1:54to communicate
44. 1:56and to move data
45. 1:57from the devices going to the cpu
46. 2:03computer system operation
47. 2:06so i o devices and the cpu can execute
48. 2:09concurrently
49. 2:11when say i o
50. 2:13this pertains to input output
51. 2:15or any peripherals attached to your
52. 2:17computer
53. 2:19so each device controller is in charge
54. 2:21of a particular device type so let's go
55. 2:23back to the previous slide here as what
56. 2:25i mentioned earlier each device here or
57. 2:28each peripheral has their own device
58. 2:31controller
59. 2:33okay
60. 2:34each device controller has a local
61. 2:36buffer once a local buffer that pertains
62. 2:38to the local memory
63. 2:40each device controller type has an
64. 2:43operating system device driver to manage
65. 2:45it
66. 2:46so every time you purchase a device for
67. 2:48instance a printer there should be a
68. 2:50device driver associated with it
69. 2:53okay so any peripherals or any hardware
70. 2:56that you want to attach to your computer
71. 2:58should have their own device driver
72. 3:02okay so sometimes the operating systems
73. 3:04provides a genetic driver for the device
74. 3:08all right
75. 3:10next so cpu moves data from and to the
76. 3:14main memory
77. 3:15to or from the local buffers and that
78. 3:18reverses via this system bus here
79. 3:24the i o is from the device the local
80. 3:27buffer of the controller
81. 3:30and then device controller informs the
82. 3:31cpu that it has finished its operation
83. 3:34by causing an interrupt so we will be
84. 3:37dealing with interrupt on this
85. 3:39video lecture
86. 3:41okay
87. 3:42there are also what you called a
88. 3:44bootstrap program okay under computer
89. 3:46system operation you've got the shared
90. 3:49memory between cpu and io cards
91. 3:52time slicing for the multi-process
92. 3:54operation
93. 3:56interrupt handling okay so clock
94. 3:59hardware software and implementation of
95. 4:02system calls
96. 4:06common functions of interrupt
97. 4:09so interrupt transfer controls to the
98. 4:12interrupt service routine generally
99. 4:14through the interrupt vector
100. 4:16which contains the address of all the
101. 4:18service routines
102. 4:20so interrupt architecture must save the
103. 4:22address of the interrupted instruction
104. 4:25a trap or exception is a
105. 4:27software-generated interrupt caused by
106. 4:30either
107. 4:31by an error or a user requests
108. 4:34so an operating system is an interrupt
109. 4:37driven
110. 4:38when you say interrupt
111. 4:40every hardware or every i o devices in a
112. 4:43computer system has their own interrupt
113. 4:45numbers or interrupt address
114. 4:47okay
115. 4:49so
116. 4:50when a device needed to signal the cpu
117. 4:53for instance a printer is running out of
118. 4:56paper
119. 4:57and then the printer will inform the
120. 4:59user hey i'm running out of paper
121. 5:02okay so it will issue an interrupt to
122. 5:05the cpu okay so causing a notification
123. 5:09to the end users
124. 5:11that's an interrupt
125. 5:12okay
126. 5:13so
127. 5:14interrupt has the highest priority when
128. 5:17it comes to the execution
129. 5:19in the cpu
130. 5:21so any device that would cause interrupt
131. 5:24will be entertained by the cpu
132. 5:26so whatever the cpu is doing or
133. 5:28processing if there would be a priority
134. 5:30interrupt then it will stop temporarily
135. 5:33the execution of the program to
136. 5:35accommodate the interrupt
137. 5:37so even users can cause an interrupt to
138. 5:40the computer systems or to the operating
139. 5:42systems
140. 5:43okay so you just have to press something
141. 5:45like control alt or control break
142. 5:48okay so if you want to
143. 5:51cause an interrupt on the execution of
144. 5:53the application or programs
145. 5:58interrupt timeline
146. 6:00okay
147. 6:01so
148. 6:02how do the cpu and the io devices
149. 6:06interact with each other
150. 6:08okay so basically your cpu
151. 6:10is running the user programs
152. 6:13it also
153. 6:15process
154. 6:17io interrupts
155. 6:19okay
156. 6:20now if the i o device is idle
157. 6:23or meaning there is no interrupt okay
158. 6:26coming from any of the i o device that
159. 6:28would cause the cpu to temporarily stop
160. 6:31or hold the execution so basically
161. 6:34your cpu is kept busy on the user
162. 6:38program execution
163. 6:40all right so if there would be an
164. 6:42interrupt coming from the device so
165. 6:44basically your cpu will accommodate
166. 6:47the interrupt address it and then
167. 6:50afterwards it will resume with the
168. 6:52execution of the user programs
169. 6:55all right so every device in a computer
170. 6:58system has what you call
171. 6:59interrupt address
172. 7:01or io
173. 7:02or we call it the irq okay
174. 7:06or interrupt request
175. 7:09okay
176. 7:12how do operating system handle interrupt
177. 7:15so the operating system preserves the
178. 7:17state of the cpu by storing the
179. 7:18registers
180. 7:20and the program counter
181. 7:21so we mentioned this on computer
182. 7:24architecture
183. 7:26our computer organization and
184. 7:27architecture
185. 7:29so determines which type of interrupt
186. 7:31has occurred it could be polling or the
187. 7:33vector interrupt system
188. 7:36all right so the interrupt would be it
189. 7:38might be coming from
190. 7:40the cpu initiating okay so who has
191. 7:43problems something like that doing some
192. 7:45polling
193. 7:46okay
194. 7:47the the action of the interrupt is
195. 7:49initiated by the cpu
196. 7:52now if the action is initiated by the i
197. 7:56o devices
198. 7:57okay so we call it
199. 8:00vectored interrupt systems
200. 8:03okay so separate segments of code
201. 8:06determine what action should be taken
202. 8:08for each type of interrupt
203. 8:13let's have an example here of an
204. 8:15interrupt driven i o cycle or interrupt
205. 8:18drive biocycle
206. 8:20so first you've got the cpu running
207. 8:24okay
208. 8:25and then device driver initiates an i o
209. 8:30so it will be transfer
210. 8:32okay
211. 8:33on the i o controller
212. 8:35so initiates an i o
213. 8:37afterwards input is ready output
214. 8:39complete or error generates an interrupt
215. 8:41signal
216. 8:42if there would be an interrupt okay so
217. 8:45that would be forwarded to the cpu so
218. 8:47cpu receiving interrupt transfer
219. 8:49controls to the interrupt handler
220. 8:52now the interrupt handler
221. 8:54processes the data
222. 8:56returns from interrupt
223. 8:59so afterwards the cpu resumes processing
224. 9:03of interrupted tasks
225. 9:06and then
226. 9:07it's a cycle or that completes the cycle
227. 9:13io structure so two methods for handling
228. 9:16io so after the i o starts
229. 9:19the control returns to the user program
230. 9:21only upon i o completion
231. 9:25okay so the second one would be io
232. 9:27starts
233. 9:29control returns to the user program
234. 9:31without waiting for the i o completion
235. 9:34okay so this two here
236. 9:37is characterized by synchronous or
237. 9:39asynchronous
238. 9:41so when you say synchronous it will not
239. 9:43proceed
240. 9:45with the execution of the remaining code
241. 9:48for the user programs okay so without
242. 9:50completing the
243. 9:52interrupt
244. 9:54okay so the other one is what's called a
245. 9:56synchronous
246. 9:57it will resume the operation of the
247. 10:00cpu for the execution of user programs
248. 10:04without waiting for the i o completion
249. 10:06something like okay so there would be an
250. 10:08interrupt
251. 10:09so let me process the interrupt okay so
252. 10:12if it is not yet then i could go back
253. 10:14to the requesting process for the users
254. 10:18so on the synchronous you have to wait
255. 10:21for the completion of the interrupt
256. 10:23before you could resume the operation
257. 10:25so that's the difference between
258. 10:27synchronous and asynchronous
259. 10:30okay so for synchronous
260. 10:32you have to wait for the completion of
261. 10:34the i o
262. 10:35prior to the resumption of the operation
263. 10:38for a synchronous
264. 10:39so without waiting for the i o
265. 10:41completion you could go back
266. 10:43okay immediately with the requesting
267. 10:45process from the users
268. 10:50so after an i o starts control returns
269. 10:53to user programs only upon i o
270. 10:55completion so this is what you call
271. 10:57synchronous here
272. 10:59okay so weight instruction i tells the
273. 11:02cpu until the next interrupt
274. 11:04so if there would be a loop a contention
275. 11:06for the memory access
276. 11:08and then at most one io request is
277. 11:11outstanding at a time no simultaneous io
278. 11:14processing
279. 11:17okay
280. 11:17now after the i o starts
281. 11:20control returns the user program without
282. 11:23waiting for the i o completion
283. 11:25so that is our
284. 11:26asynchronous here
285. 11:29okay
286. 11:30so we have what you call system called
287. 11:32request the os to allow users to wait
288. 11:35for the i o completion
289. 11:37and then you've got the device status
290. 11:39table which contains the entry for each
291. 11:41i o device
292. 11:42indicating its type address and state
293. 11:48so os indexes
294. 11:50into io device table
295. 11:52to determine device status and to modify
296. 11:55table entry
297. 11:56to include the interrupt
298. 12:05[Music]
299. 12:17you