Stallings 6e Exercise-11.10 (page number-539) I/O Management

Question

A 32-bit computer has two selector channels and one multiplexor channel. Each selector channel supports two magnetic disk and two magnetic tape units. The multiplexor channel has two line printers, two card readers, and ten VDT terminals connected to it. Assume the following transfer rates:
                                                                       Disk drive                             800 Kbytes/s
                                                                       Magnetic tape drive           200 Kbytes/s

                                                                       Line printer                          6.6 Kbytes/s
                                                                       Card reader                         1.2 Kbytes/s
                                                                       VDT                                       1 Kbytes/s
Estimate the maximum aggregate I/O transfer rate in this system

Answer 1

Selector transfer rate= max {800, 200}=800 KBps

multiplexer transfer rate= 2*6.6 + 2*1.2 + 10*1 = 13.2 + 2.4 + 10 =25.6 KBps

maximum rate=(no of select line) * 800 + (no of Multiplexer ) * 25.6 = 2*800 + 1*25.6=1600+25.6=1625.6 KBps

Answer 2

$1$ selector channel can transfer data at a time. Both cannot be active at a time

$1$ selector channel supports $=2\times 800+2\times 200+2\times 6.6+2\times 1.2+10\times 1$

$=1600+400+13.2+2.4+10=2025.6KB/sec$