ROMs - Read only memory used to stored data that does not change and
needs to be there when system first comes up.
Most ROMs organized as collections of bytes or words (single chip).
ROM-BIOS (basic I/O system) - sets the basic behavior of a system.
Data arrangement - Big-endian
Data arrangement based on design of cpu and bus.
A stored value may span several bytes of storage and may be larger
that the size of the data bus.
Little endian - The lower portion of the value being stored is s
Three features of memory that determine the amount:
Speed vs. Cost vs. Size(ammount)
High speed (cpu speed)
Referenced by "name", specific opcode or operands
Can't change number of registers without changing cpu design.
CPU's internal system.
Control unit - circuitry used to coordinate the correct functioning of
the cpu. Usually invisible to user
Clock used to synchronize the advancing of the state machine.
(Executing task in small discrete steps).
Other overhead signals
Spring 2014 - concentrate on the Bus and Networking portions of the
Pay attention to number of lines, physical vs. virtual bus, what kind
Also use wikipedia to review :
4 major types, Address, Data, Control, Power
Silicon wafers and making integrated chips.
Wikipedia topics :
Semiconductor device fabrication
Doping - creating/changing P and N layers
Etching - removal of portion of layer
Deposition - build
Negative values - Possible solutions.
(When working with signed values, all bits important.)
High bit or separate storage.
Requires different algorithm for adding and subtracting.
(Used with floats, packed BCD)
Complement each bit.
Wikipedia topic "binary multiply"
23 * 14
00010111 * 00001110
Add 23 to a sum 14 times.
Performed by accumulate and shift.
While not all bits of 2nd number examined (Not zero).
If low bit of 2nd number is 1,
Floating point limits
IEEE 754 - high bit sign bit, 8 bit biased exponent, 23 bit signficand.
Maximum absolute number size - 32 binary IEEE representation.
0 1111 1110 1111 1111 1111 1111 1111 111
Remember all 1s in exponent is special flag
Boolean Algebra - Binary logic
In the following table ! preceeding an input specifies NOT
How fetch/execute cycle processes a short instruction sequence.
As C code :
num1 = 35 + num1;
As 6502 assembler :
Clear carry flag in CCR.
Load the byte value 23h into the accumulator
Add the byte of dat
Memory units - Latches.
Hysteresis - system that is dependent on its internal state or
A memeory unit must not only toggle to the value specified, it
must hold that value after the initial set condition expired.
a. SR Latch
i. Set - Re
Clock speeds and mips
CPU uses a clock to switch between stable and transition states.
Depending on complexity of instruction
Number of clock cycles to finish instruction can vary greatly.
Semi-Simplified fetch/execute steps for 8-bit system bu
Real vs floating limits
Real number can represent any value.
Real numbers limited by writing fatigue.
Often symbolically represented to avoid writing.
Fractions or rational (ratio) numbers
Special notation for irrationals .333, pi, e
IEEE 754 standard
Special conditions not representable by scientific or float notation.
Both exponent and significand set to zero, sign bit may be either.
Exponent all 1s and significand set to zero
NAN - not a number.
Working with very large and small units of measurement.
Decimal - usually used with time issues of a system.
Terahertz (THz) - 1*10^12 cycles/sec
Gigahertz (GHz) - 1*10^9 cycles/sec - cpu processing speed.
Megahertz (MHz) - 1*10^6 cycles/sec - early
Techniques to improve on simple fetch/execute cycle.
Multiple instructions in cpu
Different steps of the F/E cycle being processed on different instructions
at same time.
Pipelining can create conflicts.
Different steps wanting same resour
Digital binary computing uses 0 and 1.
Electrical and electronic
Switches used hold bits and to make decisions.
On/Off - 1 bit. Memory
AND - both switches on.
OR - either switch on.
NOT - invert the bit or signal.
Mechanical - old fashion c
Numbers and their storage in computers.
Base or Radix numbers (positional)
One's column, 10's column, 100's column, etc.
Some base numbering systems.
Decimal : Base 10 - range of digits 0-9 (Hindu-Arabic)
Vigesimal : Base 20 - Aztec, Mayan, Ainu(East Asia
Information represented by symbols
Two general categories
Labels - alpha-numeric character sequences.
Unicode - all languages.
Generally used to label other data. Other than comparison and sorting,
little calculation done.
Dynamic Random Access memory
Capacitor based bit storage.
Short history of CPU clock speeds.