80960KB datasheet(7/39 Pages) INTEL

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80960KB

Figure 4. Multiple Register Sets Are Stored On-Chip

CACHE

ONE OF FOUR

LOCAL

LOCAL REGISTER SET

R15

1.1.7.

Floating-Point Arithmetic

In the 80960KB, 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 calcu-

lations, thereby leaving more time for other bus

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

floating-point

operations

reduced

because

separate coprocessor chip is not required.

The 80960KB 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 Local Bus

The 80960KB CPU resides on a high-bandwidth

address/data bus known as the local bus (L-Bus). The

L-Bus provides a direct communication path between

the processor and the memory and I/O subsystem

interfaces. The processor uses the L-Bus to fetch

instructions, manipulate memory and respond to

interrupts. L-Bus features include:

• 32-bit multiplexed address/data path

• Four-word burst capability which allows transfers

from 1 to 16 bytes at a time

• High

bandwidth

reads

and

writes

with

66.7 MBytes/s burst (at 25 MHz)

Table 4 defines L-bus signal names and functions;

Table 5 defines other component-support signals

such as interrupt lines.

Table 3. Sample Floating-Point Execution Times

(µs) at 25 MHz

Function

32-Bit

64-Bit

Add

0.4

0.5

Subtract

0.4

0.5

Multiply

0.7

1.3

Divide

1.3

2.9

Square Root

3.7

3.9

Arctangent

10.1

13.1

Exponent

11.3

12.5

Sine

15.2

16.6

Cosine

15.2

16.6

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