PC IO fig IO.0

Remember from PC IO==> The System Bus ( a logical construct)

PCI bus. …Backbone..most like System bus

IDE Disk controller bus- 2 disks per IDE bus (master and Slave)

SCSI Controller and bus

Expansion Bus

Parallel Port (e.g. parallel printer cable),

Serial port (USB bus),

Keyboard (make/break) contacts

Graphics Controller and Monitor

Video/Graphics card and Memory

IO_Variations

- Control Unit and Buffer

A Read = Dev -> Buffer -> Memory

A Write = Memory -> Buffer -> Dev

- 2 IO Interrupts per IO

- Match device speed to Bus speed

Minimize Buffer utilization

- Direct Memory Access (DMA) – off-load data move from CPU

IO_Variations

- Mainframe (fig IO.1 360 IO)

Many System Buses …now called “Channels”

Multiple Control Units on each Channel

Almost all Control Units (CU’s) are buffered…

not originally- but speed mismatch became a problem

Byte-Multiplexor, Selector, and then Block-Multiplexor

Control Unit can connect to multiple Channels (fig IO.2)

Control unit can connect to different channels on different CPUs

Channel to Channel connections possible if close

Channel Programs allow many complex operations without an IO

Interrupt (covered later)

Mainframe IO

Basic Addressing Structure

SIO instruction Specifies “device address”

Device address defines path to device

Today IO subsystem determines “path” to device

Minimizes bottlenecks to device

Supports higher availability in case of failures (Channels, CUs.)

Provides image of “floating” channels

Cost- longer time to initiate an IO

TPF doesn’t use it

Some IO Instructions (e.g. SIOF) release processor “early”

Mainframe IO

Notion of a sub-channel i.e. uuu a.k.a. UCW

Contains information about an IO operation to a device

e.g. CCW address, current state

Contains current path to device from processor

Mainframe IO

- CCW Format0 (64 bits..8 bytes) – (fig IO.4)

Command Code, Data address(24 bits), Flags, spare, Byte Count

Flags

CD – data chain

CC – command chain

SLI – suppress length indication (e.g. read a terminal line)

SKIP – skip data transfer

PCI - program control interrupt

IDA - data address points to first IDAW word (fig IO.5)

MIDA -data address points to first MIDAW

Mainframe IO

-CCW Format1 (64 bits..8 bytes) (fig IO 6a)

Command Code, Flags, Byte Count, Data address(31 bits)

Flags

CD – data chain

CC – command chain

SLI – suppress length indication (e.g. read a terminal line)

SKIP – skip data transfer

PCI - program control interrupt

IDA - data address points to first IDAW word (fig IO.5)

SUSPEND – suspend program ..before this command

MIDA -data address points to first MIDAW (fig IO.6 a,b)

-

Mainframe IO

IDAW and MIDAW formats IDAW1 - 0|| 31 bit address IDAW2 - 64 bit address

MIDAW – first 5 byres reserved flags bytecount 64 bit address Flags Last MIDAW in program Skip Data Transfer interrupt

Mainframe IO

- A

Mainframe IO

- A

Mainframe IO

- A