joeylib2/installer/patches/mame

MAME 0.264 patches

install.sh (component mame) applies these to the MAME 0.264 release in filename order, then builds one binary with the apple2gs and x68k drivers. The gates depend on every one of them.

Patch	What it fixes	Needed by
0001-apple2gs-scc-clock	The IIgs SCC clock, so serial RX works at rates other than 230400 baud	verify-iigs-serial.sh
0002-z80scc-rx-fifo	Makes the Z8530 receive FIFO depth selectable at run time (see below). By default it is 512 bytes, so a POLLED receiver (no RX interrupt) survives the emulator's deaf windows; JOEY_Z80SCC_RX_FIFO=3 restores the real chip's depth. Originally written for RetroNet.	IIgs serial gates (512); verify-iigs-serial-loss.sh (3)
0003-x68k-crtc-timing	The X68000 CRTC: the graphic high-speed clear's timing (the main defect), and the text raster copy firing on both hsync edges instead of only the front porch	X68000 gates and timing
0004-x68k-waitstates-rs232-mouse	Three X68000 changes that edit the same files: VRAM wait states (MAME modelled none), the RS-232C port wired to a slot so -rs232c null_modem works, and a backport of upstream commit ab6b6fc9e797 (Patrick Mackinlay, "x68k: add serial mouse"), which provides the :mouse_port:x68k:X/Y/BTN inputs	verify-x68000-serial.sh, verify-x68000-mouse.sh, X68000 timing

Receive FIFO depth (0002)

Real Z8530 silicon holds 3 received bytes (an ESCC, 8), so a real client needs interrupt-driven receive. Under emulation a polled receiver sees deaf windows no real machine has, so by default the patched MAME gives every Z8530 channel (IIgs and X68000 alike) a 512-byte receive FIFO. The environment variable JOEY_Z80SCC_RX_FIFO overrides that for one run:

JOEY_Z80SCC_RX_FIFO	Receive FIFO depth
unset or empty	512 (the default the gates rely on)
3	the real Z8530 (stock MAME's value); an ESCC keeps its real 8
N	N, clamped to 3..512; an ESCC never gets fewer than 8

MAME's ring of size N holds N-1 unread bytes, so 3 overruns on the third unread byte, one byte earlier than silicon (whose 3-byte FIFO fills first): a slightly stricter test than the real chip. When the variable is set, MAME prints <channel tag>: RX FIFO depth N (JOEY_Z80SCC_RX_FIFO) for each channel at start-up, so a log shows the depth really was applied. scripts/verify-iigs-serial-loss.sh runs with 3, because a 512-byte FIFO would hide exactly the receive loss that gate looks for.

Why the X68000 changes are one patch

They were first kept as three separate patches, but the upstream mouse backport no longer applied cleanly on top of the other two in any order, and the sources the working MAME was built from had been fixed up by hand. These four files were regenerated on 2026-09-27 by diffing that working tree against the pristine 0.264 release, so they reproduce it exactly (verified: every file applies with zero fuzz and matches byte for byte).

Probes

lua/ holds the MAME Lua probes used while developing the X68000 patches (boot check, CRTC timing, wait states). Run one with mame x68000 -bios ipl10 -autoboot_script lua/<probe>.lua.

License

The patches modify MAME and contain its code, so they are under MAME's license, the GNU GPL v2 or later, not JoeyLib's MIT License. The files 0004 adds from upstream MAME keep their own notices (BSD-3-Clause, Patrick Mackinlay). The Lua probes in lua/ are JoeyLib's own (MIT).