Enable further boot speed improvements

Makefile

@@ -31,6 +31,9 @@ else
 	$(error Invalid board type "$(BOARD)"; please specify one of [ pi0 | pi2 | pi3 | pi4 | pi4-64 ])
 endif
 
+	# Disable delay loop calibration (boot speed improvement)
+	echo "DEFINE += -DNO_CALIBRATE_DELAY" >> $(CIRCLE_CONFIG)
+
 #
 # Build circle-stdlib
 #

sdcard/config.txt

@@ -1,5 +1,7 @@
 # Remove delay and use cutdown start_cd.elf/start4cd.elf for slightly quicker boot
 boot_delay=0
+disable_splash=1
+force_eeprom_read=0
 gpu_mem=16
 
 # Ensure that the Pi 4 doesn't try to boot the Pi 3-optimized kernel (kernel8-32.img)