
1-8
MPC603e & EC603e RISC Microprocessors User's Manual
MOTOROLA
1.1.2.2 Software Features
The features of the 603e described in the following sections affect software originally
written for the 603.
1.1.2.2.1 16-Kbyte Instruction and Data Caches
The instruction and data caches of the 603e are 16 Kbytes in size, compared to the 8-Kbyte
instruction and data caches of the 603. The increase in cache size may require modification
of cache flush routines. The increase in cache size is also reflected in four-way set
associativity of the instruction and data caches in place of the two-way set associativity in
the 603.
1.1.2.2.2 Clock Configuration Available in HID1 Register
Bits 0–3 in the new HID1 register (SPR 1009) provides software read-only access to the
configuration of the PLL_CFG signals. The HID1 register is not implemented in the 603.
1.1.2.2.3 Performance Enhancements
The following enhancements provide improved performance without any required changes
to software (other than compiler optimization) or hardware designed for the 603:
Support for single-cycle store.
Addition of adder/comparator in system register unit allows dispatch and execution
of multiple integer add and compare instructions on each cycle.
Addition of a key bit (bit 12) to SRR1 to provide information about memory
protection violations prior to page table search operations. This key bit is set when
the combination of the settings in the appropriate Kx bit in the segment register and
the MSR[PR] bit indicates that when the PP bits in the PTE are set to either 00 or
01, a protection violation exists; if this is the case for a data write operation with a
DTLB miss, the changed (C) bit in the page tables should not be updated (see
Table 1-2). This reduces the time required to execute the page table search routine
since the software no longer has to explicitly read both the Kx and MSR[PR] bits to
determine whether a protection violation exists before updating the C bit.
Table 1-2. Generated SRR1 [Key] Bit
Segment Register
[Ks, Kp]
MSR[PR]
SRR1[Key] Generated
on DTLB Misses
0x
0
0
x0
1
0
1x
0
1
x1
1
1
Note that this key bit indicates a protection violation if the
PTE[pp] bits are either 00 or 01.