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N80960SB-10

EMBEDDED 32-BIT MICROPROCESSOR WITH 16-BIT BURST DATA BUS

Intel 

80960SB

REGISTER

ONE OF FOUR CACHE

LOCAL

REGISTER SETS

LOCAL REGISTER SET

r0

31

0 r15

Figure 4. Multiple Register Sets Are Stored On-Chip

1.1.7 Floating-Point Arithmetic

In the 80960SB, floating-point arithmetic has been

made an integral part of the architecture. Having the

floating-point unit integrated on chip provides two

advantages. First, it improves the performance of the

chip for floating-point applications, since no

additional bus overhead is associated with floating-

point calculations, thereby leaving more time for

other bus operations such as I/O. Second, the cost of

using floating-point operations is reduced because a

separate coprocessor chip is not required.

The 80960SB floating-point (real-number) data types

include single-precision (32-bit), double-precision

(64-bit) and extended precision (80-bit) floating-point

numbers. Any registers may be used to execute

floating-point operations.

The processor provides hardware support for both

mandatory and recommended portions of IEEE

Standard 754 for floating-point arithmetic, including

all arithmetic, exponential, logarithmic and other

transcendental functions. Table 3 shows execution

times for some representative instructions.

1.1.8 High Bandwidth Bus

The 80960SB CPU resides on a high-bandwidth

address/data bus. The bus provides a direct commu-

nication path between the processor and the

Table 3. Sample Floating-Point Execution Times

(µs) at 16 MHz

Function

Add

Subtract

Multiply

Divide

32-Bit

0.6

0.6

1.1

2.0

64-Bit

0.8

0.8

2.0

4.5

Square Root

5.8

6.1

Arctangent

15.8

20.5

Exponent

17.7

19.5

Sine

23.8

25.9

Cosine

23.8

25.9

memory and I/O subsystem interfaces. The

processor uses the bus to fetch instructions,

manipulate memory and respond to interrupts. Bus

features include:

• 16-bit data path multiplexed onto the lower bits of

the 32-bit address path

• Eight 16-bit half-word burst capability which

allows transfers from 1 to 16 bytes at a time

• High bandwidth reads and writes with

25.6 MBytes/s burst (at 16 MHz)

Table 4 defines bus signal names and functions;

Table 5 defines other component-support signals

such as interrupt lines.

6

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