diff --git a/src/test/testcommon.h b/src/test/testcommon.h
index 4ae4c900..5771f90f 100644
--- a/src/test/testcommon.h
+++ b/src/test/testcommon.h
@@ -29,7 +29,7 @@
 #define TESTOUT_ADDR 0x1f43     // PEEK(8003) -- NOTE : value is hardcoded in various places
 
 #define BLANK_SCREEN "6C8ABA272F220F00BE0E76A8659A1E30C2D3CDBE"
-#define BOOT_SCREEN  "6992DC41631290540E7175F06873BA559E938BF7"
+#define BOOT_SCREEN  "AAFB9163DD526F6E57C3BF9FCA5D5222C19E8A02"
 
 extern char mdstr[(SHA_DIGEST_LENGTH*2)+1];
 
diff --git a/src/test/testcpu.c b/src/test/testcpu.c
index bf20f3e7..cc6d82bc 100644
--- a/src/test/testcpu.c
+++ b/src/test/testcpu.c
@@ -7413,8 +7413,6 @@ GREATEST_SUITE(test_suite_cpu) {
     GREATEST_SET_TEARDOWN_CB(testcpu_teardown, NULL);
     GREATEST_SET_BREAKPOINT_CB(test_breakpoint, NULL);
 
-    srandom(time(NULL));
-
     test_common_init();
     assert(cpu_thread_id == 0 && "This test is not designed to run with alternate CPU thread");
     extern void reinitialize(void);
diff --git a/src/test/testdisk.c b/src/test/testdisk.c
index 71419af8..24d4e861 100644
--- a/src/test/testdisk.c
+++ b/src/test/testdisk.c
@@ -48,7 +48,6 @@ static void testdisk_teardown(void *arg) {
 #define EXPECTED_DISK_TRACE_SHA "FA47CC59F0CC7E5B1E938FD54A3BD8DB6C930593"
 #endif
 TEST test_boot_disk_bytes() {
-    srandom(0);
 
     const char *homedir = HOMEDIR;
     char *disk = NULL;
@@ -96,7 +95,6 @@ TEST test_boot_disk_bytes() {
 #define EXPECTED_DISK_TRACE_NIB_SHA "CE61D709A344778AB8A8DACED5A38D0D40F1E645"
 TEST test_boot_disk_bytes_nib() {
     test_setup_boot_disk(BLANK_NIB, 0);
-    srandom(0);
 
     const char *homedir = HOMEDIR;
     char *disk = NULL;
@@ -150,7 +148,6 @@ TEST test_boot_disk_bytes_nib() {
 #endif
 TEST test_boot_disk_bytes_po() {
     test_setup_boot_disk(BLANK_PO, 0);
-    srandom(0);
 
     const char *homedir = HOMEDIR;
     char *disk = NULL;
@@ -261,12 +258,12 @@ TEST test_savehello_dsk() {
     c_debugger_go();
 
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT_SHA(SAVE_SHA1);
+    WAIT_FOR_FB_SHA(SAVE_SHA1);
 
     REBOOT_TO_DOS();
     c_debugger_go();
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT_SHA(BOOT_SCREEN);
+    WAIT_FOR_FB_SHA(BOOT_SCREEN);
 
     disk6_eject(0);
 
@@ -287,12 +284,12 @@ TEST test_savehello_nib() {
     c_debugger_go();
 
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT_SHA(SAVE_SHA1);
+    WAIT_FOR_FB_SHA(SAVE_SHA1);
 
     REBOOT_TO_DOS();
     c_debugger_go();
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT_SHA(BOOT_SCREEN);
+    WAIT_FOR_FB_SHA(BOOT_SCREEN);
 
     disk6_eject(0);
 
@@ -313,12 +310,12 @@ TEST test_savehello_po() {
     c_debugger_go();
 
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT_SHA(SAVE_SHA1);
+    WAIT_FOR_FB_SHA(SAVE_SHA1);
 
     REBOOT_TO_DOS();
     c_debugger_go();
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT_SHA(BOOT_SCREEN);
+    WAIT_FOR_FB_SHA(BOOT_SCREEN);
 
     disk6_eject(0);
 
@@ -341,7 +338,6 @@ TEST test_disk_bytes_savehello_dsk() {
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] != TEST_FINISHED);
     ASSERT(apple_ii_64k[0][TESTOUT_ADDR]    == 0x00);
 
-    srandom(0);
     const char *homedir = HOMEDIR;
     char *disk = NULL;
     ASPRINTF(&disk, "%s/a2_write_disk_test_dsk.txt", homedir);
@@ -357,7 +353,7 @@ TEST test_disk_bytes_savehello_dsk() {
     c_debugger_go();
 
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT_SHA(SAVE_SHA1);
+    WAIT_FOR_FB_SHA(SAVE_SHA1);
 
     disk6_traceEnd();
 
@@ -390,7 +386,7 @@ TEST test_disk_bytes_savehello_dsk() {
     REBOOT_TO_DOS();
     c_debugger_go();
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT_SHA(BOOT_SCREEN);
+    WAIT_FOR_FB_SHA(BOOT_SCREEN);
 
     disk6_eject(0);
 
@@ -435,7 +431,6 @@ TEST test_disk_bytes_savehello_nib() {
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] != TEST_FINISHED);
     ASSERT(apple_ii_64k[0][TESTOUT_ADDR]    == 0x00);
 
-    srandom(0);
     const char *homedir = HOMEDIR;
     char *disk = NULL;
     ASPRINTF(&disk, "%s/a2_write_disk_test_nib.txt", homedir);
@@ -451,7 +446,7 @@ TEST test_disk_bytes_savehello_nib() {
     c_debugger_go();
 
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT_SHA(SAVE_SHA1);
+    WAIT_FOR_FB_SHA(SAVE_SHA1);
 
     disk6_traceEnd();
 
@@ -484,7 +479,7 @@ TEST test_disk_bytes_savehello_nib() {
     REBOOT_TO_DOS();
     c_debugger_go();
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT_SHA(BOOT_SCREEN);
+    WAIT_FOR_FB_SHA(BOOT_SCREEN);
 
     disk6_eject(0);
 
@@ -529,7 +524,6 @@ TEST test_disk_bytes_savehello_po() {
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] != TEST_FINISHED);
     ASSERT(apple_ii_64k[0][TESTOUT_ADDR]    == 0x00);
 
-    srandom(0);
     const char *homedir = HOMEDIR;
     char *disk = NULL;
     ASPRINTF(&disk, "%s/a2_write_disk_test_po.txt", homedir);
@@ -545,7 +539,7 @@ TEST test_disk_bytes_savehello_po() {
     c_debugger_go();
 
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT_SHA(SAVE_SHA1);
+    WAIT_FOR_FB_SHA(SAVE_SHA1);
 
     disk6_traceEnd();
 
@@ -578,7 +572,7 @@ TEST test_disk_bytes_savehello_po() {
     REBOOT_TO_DOS();
     c_debugger_go();
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT_SHA(BOOT_SCREEN);
+    WAIT_FOR_FB_SHA(BOOT_SCREEN);
 
     disk6_eject(0);
 
@@ -643,7 +637,6 @@ TEST test_outofspace_dsk() {
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] != TEST_FINISHED);
     ASSERT(apple_ii_64k[0][TESTOUT_ADDR]    == 0x00);
 
-    srandom(0);
     const char *homedir = HOMEDIR;
     char *disk = NULL;
     ASPRINTF(&disk, "%s/a2_oos_dsk_test.txt", homedir);
@@ -659,7 +652,7 @@ TEST test_outofspace_dsk() {
     c_debugger_go();
 
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT_SHA(NOSPACE_SHA1);
+    WAIT_FOR_FB_SHA(NOSPACE_SHA1);
 
     disk6_traceEnd();
 
@@ -692,7 +685,7 @@ TEST test_outofspace_dsk() {
     REBOOT_TO_DOS();
     c_debugger_go();
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT_SHA(BOOT_SCREEN);
+    WAIT_FOR_FB_SHA(BOOT_SCREEN);
 
     disk6_eject(0);
 
@@ -742,12 +735,12 @@ TEST test_outofspace_nib() {
     c_debugger_go();
 
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT_SHA(NOSPACE_SHA1);
+    WAIT_FOR_FB_SHA(NOSPACE_SHA1);
 
     REBOOT_TO_DOS();
     c_debugger_go();
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT_SHA(BOOT_SCREEN);
+    WAIT_FOR_FB_SHA(BOOT_SCREEN);
 
     disk6_eject(0);
 
@@ -797,12 +790,12 @@ TEST test_outofspace_po() {
     c_debugger_go();
 
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT_SHA(NOSPACE_SHA1);
+    WAIT_FOR_FB_SHA(NOSPACE_SHA1);
 
     REBOOT_TO_DOS();
     c_debugger_go();
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT_SHA(BOOT_SCREEN);
+    WAIT_FOR_FB_SHA(BOOT_SCREEN);
 
     disk6_eject(0);
 
@@ -855,7 +848,6 @@ TEST test_bload_trace_dsk() {
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] != TEST_FINISHED);
     ASSERT(apple_ii_64k[0][TESTOUT_ADDR]    == 0x00);
 
-    srandom(0);
     const char *homedir = HOMEDIR;
     char *disk = NULL;
     ASPRINTF(&disk, "%s/a2_bload_trace_test_dsk.txt", homedir);
@@ -973,7 +965,6 @@ TEST test_bload_trace_nib() {
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] != TEST_FINISHED);
     ASSERT(apple_ii_64k[0][TESTOUT_ADDR]    == 0x00);
 
-    srandom(0);
     const char *homedir = HOMEDIR;
     char *disk = NULL;
     ASPRINTF(&disk, "%s/a2_bload_trace_test_nib.txt", homedir);
@@ -1091,7 +1082,6 @@ TEST test_bload_trace_po() {
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] != TEST_FINISHED);
     ASSERT(apple_ii_64k[0][TESTOUT_ADDR]    == 0x00);
 
-    srandom(0);
     const char *homedir = HOMEDIR;
     char *disk = NULL;
     ASPRINTF(&disk, "%s/a2_bload_trace_test_po.txt", homedir);
@@ -1214,12 +1204,12 @@ TEST test_inithello_dsk() {
     c_debugger_go();
 
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT_SHA(INIT_SHA1);
+    WAIT_FOR_FB_SHA(INIT_SHA1);
 
     REBOOT_TO_DOS();
     c_debugger_go();
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT_SHA(BOOT_SCREEN);
+    WAIT_FOR_FB_SHA(BOOT_SCREEN);
 
     disk6_eject(0);
 
@@ -1239,12 +1229,12 @@ TEST test_inithello_nib() {
     c_debugger_go();
 
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT_SHA(INIT_SHA1);
+    WAIT_FOR_FB_SHA(INIT_SHA1);
 
     REBOOT_TO_DOS();
     c_debugger_go();
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT_SHA(BOOT_SCREEN);
+    WAIT_FOR_FB_SHA(BOOT_SCREEN);
 
     disk6_eject(0);
 
@@ -1264,12 +1254,12 @@ TEST test_inithello_po() {
     c_debugger_go();
 
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT_SHA(INIT_SHA1);
+    WAIT_FOR_FB_SHA(INIT_SHA1);
 
     REBOOT_TO_DOS();
     c_debugger_go();
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT_SHA(BOOT_SCREEN);
+    WAIT_FOR_FB_SHA(BOOT_SCREEN);
 
     disk6_eject(0);
 
@@ -1494,7 +1484,7 @@ TEST test_reinsert_edgecase() {
     // First verify we hit the crackscreen
     c_debugger_set_timeout(10);
     c_debugger_go();
-    ASSERT_SHA(DROL_CRACK_SCREEN_SHA);
+    WAIT_FOR_FB_SHA(DROL_CRACK_SCREEN_SHA);
 
     // re-insert
     disk6_eject(0);
diff --git a/src/test/testtrace.c b/src/test/testtrace.c
index 59c14b60..c9454508 100644
--- a/src/test/testtrace.c
+++ b/src/test/testtrace.c
@@ -248,7 +248,6 @@ TEST test_boot_disk_cputrace() {
         cpu65_trace_begin(output);
     }
 
-    srandom(0);
     BOOT_TO_DOS();
 
     cpu65_trace_end();
@@ -297,8 +296,6 @@ TEST test_boot_disk_cputrace2() { // Failing now due to difference in IRQ timing
         cpu65_trace_begin(output);
     }
 
-    srandom(0);
-
     // Poll for trace file of particular size
     c_debugger_clear_watchpoints();
     c_debugger_set_timeout(1);
@@ -364,8 +361,6 @@ TEST test_boot_disk_cputrace3() {
         cpu65_trace_begin(output);
     }
 
-    srandom(0);
-
     // Poll for trace file of particular size
     c_debugger_clear_watchpoints();
     c_debugger_set_timeout(1);
@@ -432,7 +427,6 @@ TEST test_cputrace_hello_dsk() {
         cpu65_trace_begin(output);
     }
 
-    srandom(0);
     apple_ii_64k[0][WATCHPOINT_ADDR] = 0x00;
     test_type_input_deterministically("RUN HELLO\r");
     c_debugger_go();
@@ -482,7 +476,6 @@ TEST test_cputrace_hello_nib() {
         cpu65_trace_begin(output);
     }
 
-    srandom(0);
     apple_ii_64k[0][WATCHPOINT_ADDR] = 0x00;
     test_type_input_deterministically("RUN HELLO\r");
     c_debugger_go();
@@ -532,7 +525,6 @@ TEST test_cputrace_hello_po() {
         cpu65_trace_begin(output);
     }
 
-    srandom(0);
     apple_ii_64k[0][WATCHPOINT_ADDR] = 0x00;
     test_type_input_deterministically("RUN HELLO\r");
     c_debugger_go();
@@ -581,7 +573,6 @@ TEST test_boot_disk_vmtrace() {
         vm_trace_begin(disk);
     }
 
-    srandom(0);
     BOOT_TO_DOS();
 
     vm_trace_end();
@@ -629,7 +620,6 @@ TEST test_boot_disk_vmtrace_nib() {
         vm_trace_begin(disk);
     }
 
-    srandom(0);
     BOOT_TO_DOS();
 
     vm_trace_end();
@@ -677,7 +667,6 @@ TEST test_boot_disk_vmtrace_po() {
         vm_trace_begin(disk);
     }
 
-    srandom(0);
     BOOT_TO_DOS();
 
     vm_trace_end();
diff --git a/src/test/testui.c b/src/test/testui.c
index a0608d74..660d800e 100644
--- a/src/test/testui.c
+++ b/src/test/testui.c
@@ -147,7 +147,7 @@ TEST test_save_state_1() {
     bool ret = emulator_saveState(fd);
     ASSERT(ret);
 
-    ASSERT_SHA(BOOT_SCREEN);
+    WAIT_FOR_FB_SHA(BOOT_SCREEN);
 
     TEMP_FAILURE_RETRY(close(fd));
 
@@ -190,7 +190,7 @@ TEST test_load_state_1() {
     _assert_blank_boot();
 
     ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] != TEST_FINISHED);
-    ASSERT_SHA(BOOT_SCREEN);
+    WAIT_FOR_FB_SHA(BOOT_SCREEN);
 
     TEMP_FAILURE_RETRY(close(fdState));
     TEMP_FAILURE_RETRY(close(fdA));
@@ -304,7 +304,7 @@ TEST test_load_A2VM_good1() {
     ASSERT(run_args.cpu65_sp      == 0xEA);
 
     // ASSERT framebuffer matches expected
-    ASSERT_SHA("9C654FEF2A672E16D89ED2FB80C593CD2005A026");
+    WAIT_FOR_FB_SHA("8BF579CC23A8A6D5E13F5BA3CEEE9DA7714F72B6");
 
     TEMP_FAILURE_RETRY(close(fdState));
     TEMP_FAILURE_RETRY(close(fdA));
@@ -430,7 +430,7 @@ TEST test_load_A2V2_good1() {
     mb_testAssertA2V2(mbData, mbSiz);
 
     // ASSERT framebuffer matches expected
-    ASSERT_SHA("B1CB1C5811B9C629BB077F857CC41DFA8A283E96");
+    WAIT_FOR_FB_SHA("3FB6BF44F5A7A6742550B33B627FFC5F06BAEC94");
 
     TEMP_FAILURE_RETRY(close(fdState));
     TEMP_FAILURE_RETRY(close(fdA));
@@ -556,7 +556,7 @@ TEST test_load_A2V2_good2() {
     mb_testAssertA2V2(mbData, mbSiz);
 
     // ASSERT framebuffer matches expected
-    ASSERT_SHA("7A60972EF2E95956249454402A42C12E7C8FBF7A");
+    WAIT_FOR_FB_SHA("FD20698466B30B5BE9DA298731B6B5AC2C94C56D");
 
     TEMP_FAILURE_RETRY(close(fdState));
     TEMP_FAILURE_RETRY(close(fdA));
@@ -678,7 +678,7 @@ TEST test_load_A2V2_good3() {
     mb_testAssertA2V2(mbData, mbSiz);
 
     // ASSERT framebuffer matches expected
-    ASSERT_SHA("D92EECDF3C7446097F3E884412D7911DDD968287");
+    WAIT_FOR_FB_SHA("70BFB1572C377578EAAB31AC09C4C383366628BD");
 
     TEMP_FAILURE_RETRY(close(fdState));
     TEMP_FAILURE_RETRY(close(fdA));
@@ -749,8 +749,6 @@ void test_ui(int _argc, char **_argv) {
     test_argc = _argc;
     test_argv = _argv;
 
-    srandom(time(NULL));
-
     test_common_init();
 
     pthread_t p;
diff --git a/src/test/testvm.c b/src/test/testvm.c
index 455fd850..a0619f6b 100644
--- a/src/test/testvm.c
+++ b/src/test/testvm.c
@@ -107,58 +107,6 @@ TEST test_read_random() {
     PASS();
 }
 
-#if 0
-#error this is an unstable test due to VBL refactoring ...
-TEST test_read_random2() {
-#ifdef __APPLE__
-#warning "ignoring random test on Darwin..."
-#else
-
-    srandom(0); // force a known sequence
-    BOOT_TO_DOS();
-
-    ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] != TEST_FINISHED);
-    ASSERT(apple_ii_64k[0][TESTOUT_ADDR]    == 0x00);
-
-    test_type_input("RUN TESTRND2\r");
-    c_debugger_go();
-
-    ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT(apple_ii_64k[0][TESTOUT_ADDR] == 103);
-
-    apple_ii_64k[0][WATCHPOINT_ADDR] = 0x0;
-    test_common_setup();
-    test_type_input("RUN\r");
-    c_debugger_go();
-    ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT(apple_ii_64k[0][TESTOUT_ADDR] == 198);
-
-    apple_ii_64k[0][WATCHPOINT_ADDR] = 0x0;
-    test_common_setup();
-    test_type_input("RUN\r");
-    c_debugger_go();
-    ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT(apple_ii_64k[0][TESTOUT_ADDR] == 105);
-
-    apple_ii_64k[0][WATCHPOINT_ADDR] = 0x0;
-    test_common_setup();
-    test_type_input("RUN\r");
-    c_debugger_go();
-    ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT(apple_ii_64k[0][TESTOUT_ADDR] == 115);
-
-    apple_ii_64k[0][WATCHPOINT_ADDR] = 0x0;
-    test_common_setup();
-    test_type_input("RUN\r");
-    c_debugger_go();
-    ASSERT(apple_ii_64k[0][WATCHPOINT_ADDR] == TEST_FINISHED);
-    ASSERT(apple_ii_64k[0][TESTOUT_ADDR] == 81);
-#endif
-
-    PASS();
-}
-#endif
-
 // ----------------------------------------------------------------------------
 // Softswitch tests
 
@@ -3227,20 +3175,10 @@ GREATEST_SUITE(test_suite_vm) {
 
     // TESTS --------------------------
 
-#if defined(ANDROID)
-#warning FIXME TODO ... why are these test broken on Android?!
-#else
     RUN_TESTp(test_read_keyboard);
-
     RUN_TESTp(test_clear_keyboard);
 
     RUN_TESTp(test_read_random);
-#if 0
-#error this is an unstable test due to VBL refactoring ...
-    RUN_TESTp(test_read_random2);
-#endif
-
-#endif
 
     RUN_TESTp(test_PAGE2_on,  /*80STORE*/0, /*HIRES*/0);
     RUN_TESTp(test_PAGE2_on,  /*80STORE*/0, /*HIRES*/1);
diff --git a/src/timing.c b/src/timing.c
index c211400c..bbb087e2 100644
--- a/src/timing.c
+++ b/src/timing.c
@@ -491,6 +491,7 @@ bool timing_isCPUThread(void) {
 
 void timing_startCPU(void) {
     cpu_shutting_down = false;
+    assert(cpu_thread_id == 0);
     int err = TEMP_FAILURE_RETRY(pthread_create(&cpu_thread_id, NULL, (void *)&cpu_thread, (void *)NULL));
     if (err) {
         LOG("pthread_create failed!");