From f0ff05081cd57e89d8b796aab2b7b1663bb1d7fb Mon Sep 17 00:00:00 2001
From: Matt Evans <matt@ozlabs.org>
Date: Sun, 18 Aug 2024 17:28:46 +0100
Subject: [PATCH] Add MEMSIZE build-time parameter to set memory size

By default, this is 128 (for 128KB).  Usable values are 128, 512,
1024, 2048, 4096.
---
 Makefile        |  2 ++
 README.md       | 11 +++++++----
 include/machw.h |  2 +-
 3 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/Makefile b/Makefile
index 176a8f1..37e258f 100644
--- a/Makefile
+++ b/Makefile
@@ -26,6 +26,7 @@
 #
 
 DEBUG ?= 0
+MEMSIZE ?= 128
 
 SOURCES = $(wildcard src/*.c)
 
@@ -43,6 +44,7 @@ LIBS = $(SDL_LIBS) -lm
 
 INCLUDEFLAGS = -Iinclude/ -I$(MUSASHI) $(SDL_CFLAGS) -DMUSASHI_CNF=\"../include/m68kconf.h\"
 INCLUDEFLAGS += -DENABLE_DASM=1
+INCLUDEFLAGS += -DUMAC_MEMSIZE=$(MEMSIZE)
 CFLAGS = $(INCLUDEFLAGS) -Wall -Wextra -pedantic -DSIM
 
 ifeq ($(DEBUG),1)
diff --git a/README.md b/README.md
index 2da86f4..f4dc07e 100644
--- a/README.md
+++ b/README.md
@@ -33,12 +33,14 @@ This emulates the following hardware:
   * VIA shift register for keyboard
   * SCC DCD pin change interrupts, for mouse
   * Paravirtualised disc storage
-  * Defaults to 128K of RAM, but will run as a Mac 512K by changing
-    a `#define` (`RAM_SIZE`).
+  * Defaults to 128K of RAM, but will run as a Mac 512K by building
+    with `MEMSIZE=512`.  Or, you could use 1024, 2048, or 4096 to
+    make a 1/2/4MB Mac Plus.
 
 There's no emulation for:
 
   * IWM/realistic floppy drives
+  * SCSI; the machine is sort of like a Mac Plus without SCSI.
   * More than one disc, or runtime image-switching
   * Sound (a lot of work for a beep)
   * VIA timers (Space Invaders runs too fast, probably because of this)
@@ -110,7 +112,8 @@ make
 ```
 
 No surprises here.  No autoconf either.  :D You can add a `DEBUG=1` to
-make to compile in debug spew.
+make to compile in debug spew, and add `MEMSIZE=<size_in_KB>` to control
+the amount of memory.
 
 This will configure and build _Musashi_, umac, and `unix_main.c` as
 the SDL2 frontend.  The _Musashi_ build generates a few files
@@ -185,7 +188,7 @@ pitfalls/observations:
     (e.g. `Open()`, `Prime()`, `Control()`, `Status()`) the call is
     routed to host-side C code in `disc.c`.  The emulation code
     doesn't support any of the advanced things a driver can be asked
-    to do, such as formatting – just read/[not yet write] of a block.
+    to do, such as formatting – just read/write of a block.
     When the disc is asked to be ejected, a `umac` callback is called;
     currently this just exits the emulator.  The beginnings of
     multi-disc support are there, but not enabled – again, bare
diff --git a/include/machw.h b/include/machw.h
index 424a517..813030b 100644
--- a/include/machw.h
+++ b/include/machw.h
@@ -31,7 +31,7 @@
 #include "rom.h"
 
 #define ROM_ADDR        0x400000        /* Regular base (and 0, when overlay=0 */
-#define RAM_SIZE        (0x20000*1)
+#define RAM_SIZE        (1024*UMAC_MEMSIZE)
 #define RAM_HIGH_ADDR   0x600000
 
 #define PV_SONY_ADDR    0xc00069        /* Magic address for replacement driver PV ops */