@ecto Thanks for the configs, I did some analysis. First: I should have mentioned that after the change of this line to make -j4 PLATFORM="rpi4-sdl2" the amiberry must be rebuilded and installed (sudo ./retropie_packages.sh amiberry), please also make sure you use v4.1.6 of Amiberry and not the current master, just in case you missed it.
From the configs I found these differences to mine:
In amiberry.conf:
Diffs mine (which are also the default amiberry.conf settings) starting with - (red), yours starting with + (green)
$ diff -bB -u --color amiberry.conf amiberry.conf_usr_ecto
--- amiberry.conf 2022-03-04 18:10:15.818541075 +0100
+++ amiberry.conf_usr_ecto 2022-03-04 17:57:08.000000000 +0100
@@ -5,7 +5,7 @@
rctrl_as_ramiga=no
gui_joystick_control=yes
use_sdl2_render_thread=no
-default_multithreaded_drawing=yes
+use_drawing_thread=no
input_default_mouse_speed=100
input_keyboard_as_joystick_stop_keypresses=no
default_open_gui_key=F12
@@ -15,11 +15,11 @@
rotation_angle=0
default_horizontal_centering=yes
default_vertical_centering=yes
-default_scaling_method=-1
+default_scaling_method=0
default_frameskip=no
default_correct_aspect_ratio=yes
default_auto_height=no
-default_width=640
+default_width=720
default_height=512
default_fullscreen_mode=2
default_stereo_separation=7
@@ -38,49 +38,3 @@
default_whd_buttonwait=no
default_whd_showsplash=yes
default_whd_configdelay=0
You may change them one by one to my settings and retest after each change.
In config.txt:
I have seen you run a high overclocking. Maybe you can disable it for the tests on amiberry. I had different downside effects on Amiberry (3.3 and 4.1.6 when OC over 1950Mhz) (on my 4.19 kernel with fake KMS).
I assume you are using a (4k?) TV for the Raspberry. Can you try with a full HD computer monitor?
E.g., set hdmi_group=2, hdmi_mode=82 or set only hdmi_group=0, I guess you know the switches. --> https://www.raspberrypi.com/documentation/computers/config_txt.html#hdmi_group
And I did not review/change the WHDLoad file. I just let it sit there. You should however update it from time to time (within the Amiberry UI menu), if you haven't done it recently.
HTH