Multi-Issue

GSys LibreCore can elaborate more than one issue port so independent ops leave decode/issue in the same cycle. Width is a config product choice, not a hardwired pipeline rewrite.

Knobs

Concept	Config / code	Notes
Issue width	`NrIssuePorts`	Scaled structures in build_config / packages
Superscalar baseline	`SuperscalarEn`	Often auto-selects 1 vs 2 issue
Scoreboard / load / store depth	`NrScoreboardEntries`, `NrLoadBufEntries`, `MaxOutstandingStores`	Must grow with MLP and width
OoO backend	`OoOEn`	Multi-issue with rename/IQ when on; without when off

When OoOEn=0, multi-issue is still an in-order multi-issue product (dual or wider issue with scoreboard discipline). When OoOEn=1, issue width feeds the rename/IQ/ROB path — see Out-of-Order.

Pipeline impact

frontend (wider fetch useful)
    → ID / decode (multi-op)
    → issue / IRO (NrIssuePorts)
    → EX ports / WB
    → commit (multi-commit ports where configured)

Areas that must scale with width:

Operand read ports and forwarding
Functional unit arbitration
Scoreboard allocation and RAW checks (or OoO rename bypass of arch RAW)
Commit free of physical registers (OoO packages)

Product packages

Examples (confirm names in core/include/):

Profile	Typical width	Notes
Default `cv64a6_imafdc_sv39`	1 (or 2 if superscalar)	Identity-lean path
`g6lc64_ooo_int`	2	Integer-only OoO bring-up baseline
`g6lc64_smt2_ooo_int`	2	Production SMT2 over OoO (mixed residency, ring 16)
`g6lc64_ooo`	2	Dual-issue OoO lite — legal single-hart FP since M4
`g6lc64_ooo_server`	4	Server OoO width — opt-in / unqualified; the 4-issue overlay on int2_l3 (M7) is not promoted until the fast-squash recovery lands
Server math packages	2+	Dual-issue + L2/H/Sstc stack

Timing and power

Wider issue multiplies:

Register file / PRF ports
Wakeup and select networks (especially under OoO)
Commit / free bandwidth

Treat every width step as a timing closure event. Use g6lc-build verify on the target package and optional structural FO4 via timings.

Verification

g6lc-build verify --target <wide_pkg>
# OoO-wide directed path (optional / lengthy):
g6lc-build test --suite ooo-l3-tests

Directed ILP and multi-issue stress live under verif/tests/custom/ for OoO packages; open-source smoke remains the minimum for every change.

Frontend Extensions Out-of-Order