IBM POWERPC 750GL - Manual (Page 81)

User’s Manual
IBM PowerPC 750GX and 750GL RISC Microprocessor
gx_02.fm.(1.2)
March 27, 2006 Programming Model
Page 81 of 377
2.1.5 L2 Cache Control Register (L2CR)
The L2 Cache Control Register is a supervisor-level, implementation-specific SPR used to configure and
operate the L2 cache. It is cleared by a hard reset or power-on reset.
The L2 cache interface is described in Chapter 9, L2 Cache, on page 323. The L2CR register can be
accessed with the mtspr and mfspr instructions using SPR 1017.
L2E CE
Reserved
DO GI Res
e
rv
ed
WT TS
Reserved
LO
CK
LO
LOCK
HI
SH
E
E
SH
E
R
R
LOCK
IO Res
e
rv
ed
IP
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Bits Field Name Description
0 L2E
L2 enable. Enables and disables the operation of the L2 cache, starting with the next
transaction.
1 CE
L2 double-bit error checkstop enable. L2 cache double-bit errors can result in a checkstop
condition.
2:8 Reserved Reserved.
9 DO
L2 data-only. Setting this bit inhibits the caching of instructions in the L2 cache. All
accesses from the L1 instruction cache are treated as cache-inhibited by the L2 cache
(bypass L2 cache, no L2 tag look-up performed).
10 GI
L2 global invalidate. Setting GI invalidates the L2 cache globally by clearing the L2 status
bits.
11 Reserved Reserved.
12 WT
L2 write-through. Setting WT selects write-through mode (rather than the default copy-
back mode) so all writes to the L2 cache also write through to the 60x bus.
13 TS
L2 test support. Setting TS causes cache-block pushes from the L1 data cache that result
from dcbf and dcbst instructions to be written only into the L2 cache and marked valid,
rather than being written only to the 60x bus and marked invalid in the L2 cache in case of
a hit. If TS is set, it causes single-beat store operations that miss in the L2 cache to be
discarded.
14:19 Reserved Reserved.
20 LOCKLO
Lock lower half of the L2 cache (ways 0 and 1). This provides a form of backward compat-
ibility for L2 locking. New applications should use bits 24:25.
21 LOCKHI
Lock upper half of the L2 cache (ways 2 and 3). This provides a form of backward com-
patibility for L2 locking. New applications should use bits 26:27.
22 SHEE
Snoop hit in locked line error enable. Enables a snoop hit in a locked line to raise a
machine check.
23 SHERR
Snoop hit in locked line error. Set by a snoop hit to a locked line. Once set, this sticky bit
remains set until cleared by a mtspr to the L2CR.
24:27 LOCK
Cache lock control. Setting one or more of bits 24, 25, 26, and 27 locks ways 0, 1, 2, and
3 respectively
28 IO
L2 instruction-only. Setting this bit inhibits the caching of data in the L2 cache. All
accesses from the L1 data cache are treated as cache-inhibited by the L2 cache (bypass
L2 cache, no L2 tag look-up performed).
29:30 Reserved Reserved.
31 IP
L2 global invalidate in progress (read only). This read-only bit indicates whether an L2
global invalidate is occurring.