diff --git a/Makefile b/Makefile
index 692747fa3..819464fb7 100644
--- a/Makefile
+++ b/Makefile
@@ -1,15 +1,22 @@
 .PHONY: vendor
 
-JOBS=4
-MAKE=make -j $(JOBS)
-
-BOARDLOADER_BUILD_DIR=micropython/boardloader/build
-BOOTLOADER_BUILD_DIR=micropython/bootloader/build
-FIRMWARE_BUILD_DIR=micropython/firmware/build
-
-TREZORHAL_PORT_OPTS=FROZEN_MPY_DIR=src DEBUG=1
-UNIX_PORT_OPTS=MICROPY_FORCE_32BIT=1 MICROPY_PY_BTREE=0 MICROPY_PY_TERMIOS=0 MICROPY_PY_FFI=0 MICROPY_PY_USSL=0 MICROPY_SSL_AXTLS=0 DEBUG=1
-CROSS_PORT_OPTS=MICROPY_FORCE_32BIT=1
+JOBS = 4
+MAKE = make -j $(JOBS)
+
+BOARDLOADER_BUILD_DIR = micropython/boardloader/build
+BOOTLOADER_BUILD_DIR  = micropython/bootloader/build
+FIRMWARE_BUILD_DIR    = micropython/firmware/build
+
+TREZORHAL_PORT_OPTS   = FROZEN_MPY_DIR=src DEBUG=1
+CROSS_PORT_OPTS       = MICROPY_FORCE_32BIT=1
+UNIX_PORT_OPTS        = MICROPY_PY_BTREE=0 MICROPY_PY_TERMIOS=0 MICROPY_PY_FFI=0 MICROPY_PY_USSL=0 MICROPY_SSL_AXTLS=0 DEBUG=1
+
+UNAME_S := $(shell uname -s)
+ifeq ($(UNAME_S),Darwin)
+UNIX_PORT_OPTS += MICROPY_FORCE_32BIT=0
+else
+UNIX_PORT_OPTS += MICROPY_FORCE_32BIT=1
+endif
 
 ## help commands:
 
diff --git a/README.md b/README.md
index 9c7599f15..8bfedd97f 100644
--- a/README.md
+++ b/README.md
@@ -39,8 +39,15 @@ make build_unix
 
 ### OS X
 
+Install SDL2 using DMG installer from [SDL download page](https://www.libsdl.org/download-2.0.php) or run the following if you use Homebrew:
+
+```sh
+brew install sdl2 sdl2_image
+```
+
+Build the emulator:
+
 ```sh
-brew install --universal sdl2 sdl2_image
 make build_unix
 ```
 
diff --git a/emu.sh b/emu.sh
index 4742bb36f..854fb0db2 100755
--- a/emu.sh
+++ b/emu.sh
@@ -2,10 +2,15 @@
 
 source emu.config 2>/dev/null
 
+EXE=vendor/micropython/unix/micropython
 OPTLEVEL="${OPTLEVEL:-0}"
-HEAPSIZE="${HEAPSIZE:-100000}"
 MAIN="${MAIN:-main.py}"
 BROWSER="${BROWSER:-chromium}"
+if file $EXE | grep -q 80386 ; then
+HEAPSIZE="${HEAPSIZE:-100000}"
+else
+HEAPSIZE="${HEAPSIZE:-1000000}"
+fi
 
 ARGS="-O${OPTLEVEL} -X heapsize=${HEAPSIZE}"
 
@@ -14,12 +19,12 @@ cd `dirname $0`/src
 case "$1" in
     "-d")
         shift
-        gdb --args ../vendor/micropython/unix/micropython $ARGS $* $MAIN
+        gdb --args ../$EXE $ARGS $* $MAIN
         ;;
     "-r")
         shift
         while true; do
-            ../vendor/micropython/unix/micropython $ARGS $* $MAIN &
+            ../$EXE $ARGS $* $MAIN &
             UPY_PID=$!
             find -name '*.py' | inotifywait -q -e close_write --fromfile -
             echo Restarting ...
@@ -28,12 +33,12 @@ case "$1" in
         ;;
     "-p")
         shift
-        ../vendor/micropython/unix/micropython $ARGS $* $MAIN &
+        ../$EXE $ARGS $* $MAIN &
         perf record -F 100 -p $! -g -- sleep 600
         perf script > perf.trace
         ../vendor/flamegraph/stackcollapse-perf.pl perf.trace | ../vendor/flamegraph/flamegraph.pl > perf.svg
         $BROWSER perf.svg
         ;;
     *)
-        ../vendor/micropython/unix/micropython $ARGS $* $MAIN
+        ../$EXE $ARGS $* $MAIN
 esac