Chapters 8

1
Chapters 8 9

• (partial coverage)

2
Interfacing Processors and Peripherals

• I/O Design affected by many factors
  (expandability, resilience)
• Performance access latency throughput
  connection between devices and the system the
  memory hierarchy the operating system
• A variety of different users (e.g., banks,
  supercomputers, engineers)

3
?????
4
I/O

• Important but neglected The difficulties in
  assessing and designing I/O systems have often
  relegated (??)I/O to second class
  status courses in every aspect of computing,
  from programming to computer architecture often
  ignore I/O or give it scanty coverage textbook
  s leave the subject to near the end, making it
  easier for students and instructors to skip it!
• GUILTY! we wont be looking at I/O in much
  detail be sure and read Chapter 8 in its
  entirety. you should probably take a
  networking and/or storage class!
• relegated ?? scanty ???

5
I/O Devices

• Very diverse devices behavior (i.e., input vs.
  output) partner (who is at the other end?)
  data rate

6
I/O Example Disk Drives

• To access data seek position head over the
  proper track (3 to 14 ms. avg.) rotational
  latency wait for desired sector (5K-15K /
  RPM) transfer grab the data (one or more
  sectors) 30 to 80 MB/sec

7
I/O Example Buses

• Shared communication link (one or more wires)
• Difficult design may be bottleneck length
  of the bus number of devices tradeoffs
  (buffers for higher bandwidth increases
  latency) support for many different devices
  cost
• Types of buses processor-memory (short high
  speed, custom design) backplane (??,high
  speed, often standardized, e.g., PCI) I/O
  (lengthy, different devices, e.g., USB, Firewire)
• Synchronous vs. Asynchronous use a clock and a
  synchronous protocol, fast and small but every
  device must operate at same rate and clock
  skew(???) requires the bus to be short dont
  use a clock and instead use handshaking

8
I/O Bus Standards

• Today we have two dominant bus standards
  

9
Other important issues

• Bus Arbitration daisy chain(???)arbitration
  (not very fair) centralized arbitration
  (requires an arbiter ???), e.g., PCI collision
  detection, e.g., Ethernet
• Operating system polling interrupts
  direct memory access (DMA)
• Performance Analysis techniques queuing
  theory simulation analysis, i.e., find the
  weakest link (see I/O System Design)
• Many new developments

10
Pentium 4- I/O Options
11
Pentium 4
12
?????????

• ?????,???????????????
• ????????vs???????????????
• i?????????????(Standard Parallel
  Port)????(??COM) ??????8????,?????????????1????,?
  ???????
• ????????????
• 1981????PC??ISA?????????????,8?,8.33MHz,?????
  286?,???16?,????,??????8.33MHz??????386????
• 486??,????PCI?VESA????,????(32?)
• PCI????????????,?????????,PCI???????(25MHz?30MHz?3
  3MHz)?
• VESA????????,???????
• PCI??????Pentium??PC?????,??????????????????PCI???
  

13
?????????

• ???????????
• 1????????????
• ???????????????????,?????????,????????????????????
  ?????,????????,????????????????
• ??,?????????????????????
• 2???????????????????????,????
• ??IEEE 1284????????300KB/s,?RS-232C??????????????
  ?20KB/s,???????????????????,???????????????,?????R
  S-232?????
• USB,?????????
• 1995?,?Compaq?Intel?Microsoft?NEC????????USB??????
  ?PC??,1998?????????????
• USB?RS-232C???100???,?????????????,???????????????
  

14
?????????

• USB?????????,??????????????????,???????(differenti
  al signal)????
• ???????????????????????,????????????USB???????????
  ??????,????????
• ????????????????????????
• ?????????
• ??USB?FireWire,???????????????????,????????????I/O
  ??,????????????????????
• CPU???????,???????,??????????????????????????????
• Intel?PCI Express?AMD?HyperTansport??RAMBUS???redw
  ood?I/O????????????????(LVDS)?????????????

15
?????????

• SATA,???????
• ?ATA33??,??40??????,????????,???????????
• ?ATA66??,ATA????????????1?????????????????,???????
  ?????????C2,????????????,??PATA????????????133MHz?
  ?
• ??,ATA??????????????????
• SATA?Intel???IDF2000????,??Intel??APT?Dell?IBM?Sea
  gate??Maxtor?????,?2001??????SATA
  1.0??????IDF2002?,SATA 2.0????????
• SATA????4?????3???,??7?????????SATA
  1.0??,??????150MB/s,?ATA133??133MB/s???????,????SA
  TA 2.0/3.0????300MB/s??600MB/s???????????????,SATA
  ?????????????????

16
?????????

• FireWire,????????
• FireWire(??)?1986???????????,1995??????????????(IE
  EE)??IEEE 1394??,?USB???????????????
• FireWire????????????????????,?????????DV?DC?DVD???
  ??????????????????
• FireWire????6???,??????????????,????????????SONY??
  ?FireWire????,?????????,?????????????FireWire,????
  i.Link?
• FireWire??????USB??,??????400Mbps,?????4.5????,IEE
  E 1394b????????????800Mbps,?IEEE
  1394-2000????,???????????????1.6Gbps,?????????????
  ??????100??

17
Fallacies and Pitfalls ?????

• Fallacy the rated mean time to failure(MTTF
  ??????) of disks is 1,200,000 hours, so disks
  practically never fail.
• Fallacy magnetic disk storage(?????) is on its
  last legs, will be replaced.
• Fallacy A 100 MB/sec bus can transfer 100
  MB/sec.
• ?????????,????????
• ?????????????????
• Pitfall Moving functions from the CPU to the
  I/O processor, expecting to improve performance
  without analysis.
• ??I/O???????I/O?????????CPU

18
Multiprocessors

• Idea create powerful computers by connecting
  many smaller ones good news works for
  timesharing ????????? (better than
  supercomputer) bad news its really hard to
  write good concurrent programs many commercial
  failures

19
Questions

• How do parallel processors share data? single
  address space ???? (SMP vs. NUMA-????????)
  message passing(??clusters,?????,?????????)
• How do parallel processors coordinate?
  synchronization (locks, semaphores ??) built
  into send / receive primitives ????(????)
• operating system protocols
• How are they implemented? connected by a
  single bus connected by a network

20
Supercomputers
Plot of top 500 supercomputer sites over a decade
21
Topologies

• ???????????????
• ?????????????????????????????
• ????????????????????????
• ?????
• ???????,???-?????????

22
Topologies
23
Topologies
24
Clusters

• Constructed from whole computers
• Independent, scalable networks
• Strengths
• Many applications amenable (????) to loosely
  coupled machines
• Exploit (??) local area networks
• Cost effective / Easy to expand
• Weaknesses
• Administration costs not necessarily lower
• Connected using I/O bus
• Highly available due to separation of memories
• In theory, we should be able to do better

25
Google

• Serve an average of 1000 queries per second
• Google uses 6,000 processors and 12,000 disks
• Two sites in silicon valley, two in Virginia
• Each site connected to internet using OC48 (2488
  Mbit/sec)
• Reliability
• On an average day, 20 machines need rebooted
  (software error)
• 2 of the machines replaced each year
• In some sense(??????), simple ideas well
  executed. Better (and cheaper) than other
  approaches involving increased complexity

26
Concluding Remarks

• Evolution vs. Revolution ?????
• ?????????????,?????????????
• More often the expense of innovation comes from
  being too disruptive to computer users

27
Concluding Remarks

• Acceptance of hardware ideas requires acceptance
  by software people therefore hardware people
  should learn about software. And if software
  people want good machines, they must learn more
  about hardware to be able to communicate with and
  thereby influence hardware engineers.
• ????????-????????????????-?????/?????
• ????????????,??,????????????????????????????????,
  ??,??????????????
• ????????????,??????????,????????????????