79RC5000 MULTI-ISSUE 64-BITMICROPROCESSOR
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RC5000 Computational Units
The RC5000 contains the following computational units:
Integer ALU. The RC5000 implements a full, single-cycle 64-bit
ALU for all integer ALU functions other than multiply and divide.
Bypassing is used to support back-to-back ALU operations at the
full pipeline rate, without requiring stalls for data dependencies.
Integer Multiply/Divide Unit. This unit is separated from the
primary ALU, to allow these longer latency operations to run in
parallel with other operations. The pipeline stalls only if an attempt
to access the HI or LO registers is made before the operation
completes.
Floating-point ALU. This unit is responsible for all CP1/CP1X
ALU operations other than DIV/SQRT. The unit is pipelined to allow
a single-cycle repeat rate for single-precision operations
Floating-point DIV/SQRT unit. This unit is separated from the
other floating-point ALU, so that these long latency operations do
not prevent the issue of other floating point operations.
In addition, the RC5000 implements separate logical units to
implement loads, stores, and branches.
Operating frequency
The input clock operates in a frequency range of 33MHz to
100MHz. The pipeline frequency for the RC5000 is 2 to 8 times the
input clock (up to the maximum for the speed grade of CPU).
Thermal considerations
The RC5000 utilizes special packaging techniques, to improve
the thermal properties of high-speed processors. The RC5000 is
packaged using cavity down packaging in a 223-pin PGA package
with integral thermal slug, and a 272-pin BGA package. These
packages effectively dissipate the power of the CPU, increasing
device reliability.
The RC5000 utilizes an all-aluminum package with the die
attached to a normal copper lead frame mounted to the aluminum
casing. Due to the heat-spreading effect of the aluminum, the
package allows for an efficient thermal transfer between the die
and the case. The aluminum offers less internal resistance from
one end of the package to the other, reducing the temperature
gradient across the package and therefore presenting a greater
area for convection and conduction to the PCB for a given temper-
ature. Even nominal amounts of airflow will dramatically reduce the
junction temperature of the die, resulting in cooler operation.
The RC5000 is guaranteed in a case temperature range of 0° to
+85° C. The type of package, speed (power) of the device, and
airflow conditions affect the equivalent ambient temperature condi-
tions that will meet this specification.
The equivalent allowable ambient temperature, TA, can be
calculated using the thermal resistance from case to ambient
(∅CA) of the given package.
The following equation relates ambient and case temperatures:
TA = TC - P * ∅CA
where P is the maximum power consumption at hot temperature,
calculated by using the maximum ICC specification for the device.
Typical values for ∅CA at various airflows are shown in Table 1.
Table 2: Thermal Resistance (∅∅CA) at Various Airflows
Note: The RC5000 implements advanced power management to
substantially reduce the average power dissipation of the device. This
operation is described in the IDT79RV5000 RISC Microprocessor
Reference Manual.
Note:
Per the RC5000 Documentation errata, Revicion 1.0, dated
February 1999 and per the RC5000 Device errata, dated February
1999, mode bits 20, 33 and 37 must be set to 1.
Revision history
Changes to version dated January 1996:
Pin Description section:
-Corrected pin list for Clock/Control, Initialization, and
Secondary Cache interfaces.
Advance Pin-Out section:
-Changed pins AA19 and AA21 from Vcc to Vss.
Changes to version dated March 1997:
-Upgraded data sheet status from “Preliminary” to Final.
-Added section on thermal considerations
-Added section on absolute maximum ratings
Changes to version dated June 1997:
-Revised Power Consumption and System Interface Param-
eters
Changes to version dated September 1997:
-Added user notation on Boot Mode Bits 20 and 33 for 200
MHz frequency
Changes to version dated June 1998:
-Added 250 MHz
-Changed naming conventions
Changes to version dated June 1999:
-Added 267 MHz and 300 MHz
∅∅CA
Airflow (ft/min) 0200 400 600 800 1000
PGA 16 7532.5 2
BGA 14 6 4 3 2.5 2