Palcode Restrictions And Guidelines - Compaq 21264 Hardware Reference Manual

PALcode Restrictions and Guidelines

D.1 Restriction 1 : Reset Sequence Required by Retire Logic and
For convenience of implementation, the Ibox retire logic done status bits are not initial-
ized during reset. Instead, as shown in the example below, the first batch of valid
instructions sweeps through inum-space and initializes these bits. The 80 status bits
(one for each inflight instruction) must be marked not done by the first 80 instructions
mapped after reset, and later marked done when those instructions are retired. There-
fore, the first 20 fetch blocks must contain four valid instructions each, and must not
contain any retire logic NOP instructions.
reset:
** (1) Initialize 80 retirator "done" status bits and
** the integer and floating mapper destinations.
** (2) Do A MTPR ITB_IA, which turns on the mapper source
** enables.
** (3) Create a map stall to complete the ITB_IA.
**
** State after execution of this code:
** retirator initialized
** destinations mapped
** source mapping enabled
** itb flushed
**
** The PALcode need not assume the following since the SROM is not
** required to do these:
** dtb
** dtb_asn0
** dtb_asn1
** dtb_alt_mode
*/
/*
** Initialize retirator and destination map, doing 80 retires.
*/
addq
addq
addt
mult
addq
addq
Alpha 21264/EV67 Hardware Reference Manual
Mapper
flushed
0
0
0
r31,r31,r0 /* initialize Int. Reg. 0*/
r31,r31,r1 /* initialize Int. Reg. 1*/
f31,f31,f0 /* initialize F.P. Reg. 0*/
f31,f31,f1 /* initialize F.P. Reg. 1*/
r31,r31,r2 /* initialize Int. Reg. 2*/
r31,r31,r3 /* initialize Int. Reg. 3*/
PALcode Restrictions and Guidelines
D
D–1