diff --git a/Makefile.am b/Makefile.am
index e2df2f08..aaf6b24e 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -92,7 +92,7 @@ src/x86/glue.S: src/disk.c src/misc.c src/display.c src/vm.c src/cpu-supp.c @AUD
 LOG_DRIVER = testcpu  ## hack TODO/FIXME ... should be wrapper shell script accepting standard GNU testing API args ...
 
 A2_TEST_SOURCES = $(apple2ix_SOURCES) src/test/testcommon.c
-A2_TEST_CFLAGS = -DTESTING=1 -DCPU_TRACING=1 -Isrc/test
+A2_TEST_CFLAGS = -DTESTING=1 -DCPU_TRACING=1 -DDISK_TRACING=1 -Isrc/test
 
 TESTS          = testcpu testdisplay testvm
 check_PROGRAMS = testcpu testdisplay testvm
diff --git a/src/disk.c b/src/disk.c
index 158cd38b..631730f6 100644
--- a/src/disk.c
+++ b/src/disk.c
@@ -21,7 +21,7 @@
 #define NIB_SIZE 232960
 #define DSK_SIZE 143360
 
-#ifdef TESTING
+#if DISK_TRACING
 static FILE *test_read_fp = NULL;
 static FILE *test_write_fp = NULL;
 #endif
@@ -114,7 +114,7 @@ void c_init_6(void) {
 #endif
 }
 
-#ifdef TESTING
+#if DISK_TRACING
 void c_begin_disk_trace_6(const char *read_file, const char *write_file) {
     if (read_file) {
         test_read_fp = fopen(read_file, "w");
@@ -136,6 +136,14 @@ void c_end_disk_trace_6(void) {
         test_write_fp = NULL;
     }
 }
+
+void c_toggle_disk_trace_6(const char *read_file, const char *write_file) {
+    if (test_read_fp) {
+        c_end_disk_trace_6();
+    } else {
+        c_begin_disk_trace_6(read_file, write_file);
+    }
+}
 #endif
 
 /* -------------------------------------------------------------------------
@@ -260,9 +268,9 @@ unsigned char c_read_nibblized_6_6(void) {
         fseek(disk6.disk[disk6.drive].fp, -2 * PHASE_BYTES, SEEK_CUR);
     }
 
-#ifdef TESTING
+#if DISK_TRACING
     if (test_read_fp) {
-        fputc(ch, test_read_fp);
+        fprintf(test_read_fp, "%02X", ch);
         fflush(test_read_fp);
     }
 #endif
@@ -367,6 +375,11 @@ unsigned char c_read_normal_6(void) {
             /* Set file position variable */
             disk6.disk[disk6.drive].file_pos = 256 * 16 * (disk6.disk[disk6.drive].phase >> 1) +
                                                256 * skew_table_6[ disk6.disk[disk6.drive].sector ];
+#if DISK_TRACING
+            if (test_read_fp) {
+                fprintf(test_read_fp,  "\nTRK:%02X SECTOR:%02X SKEW:%02X (FILE_POS:%d)\n", disk6.disk[disk6.drive].phase, disk6.disk[disk6.drive].sector, skew_table_6[ disk6.disk[disk6.drive].sector ], disk6.disk[disk6.drive].file_pos);
+            }
+#endif
 
             /* File large enough? */
             if (disk6.disk[disk6.drive].file_pos + 255 > disk6.disk[disk6.drive].file_size) {
@@ -427,9 +440,9 @@ unsigned char c_read_normal_6(void) {
         disk6.disk[disk6.drive].run_byte = 0;
     }
 
-#ifdef TESTING
+#if DISK_TRACING
     if (test_read_fp) {
-        fputc(value, test_read_fp);
+        fprintf(test_read_fp, "%02X", value);
         fflush(test_read_fp);
     }
 #endif
@@ -451,9 +464,9 @@ void c_write_nibblized_6_6(void) {
 
     fputc(disk6.disk_byte, disk6.disk[disk6.drive].fp);
 
-#ifdef TESTING
+#if DISK_TRACING
     if (test_write_fp) {
-        fputc(disk6.disk_byte, test_write_fp);
+        fprintf(test_read_fp, "%02X", disk6.disk_byte);
         fflush(test_write_fp);
     }
 #endif
@@ -565,9 +578,12 @@ void c_write_normal_6(void) {
 
             /* Write sector */
             fwrite(disk6.disk_data, 1, 256, disk6.disk[disk6.drive].fp);
-#ifdef TESTING
+#if DISK_TRACING
             if (test_write_fp) {
-                fwrite(disk6.disk_data, 1, 256, test_write_fp);
+                fprintf(test_write_fp, "\nTRK:%02X SECTOR:%02X SKEW:%02X (FILE_POS:%d)\n", disk6.disk[disk6.drive].phase, disk6.disk[disk6.drive].sector, skew_table_6[ disk6.disk[disk6.drive].sector ], disk6.disk[disk6.drive].file_pos);
+                for (unsigned int i=0; i<256; i++) {
+                    fprintf(test_write_fp, "%02X", disk6.disk_data[i]);
+                }
                 fflush(test_write_fp);
             }
 #endif
diff --git a/src/disk.h b/src/disk.h
index 2acbfbc5..6a4ad08e 100644
--- a/src/disk.h
+++ b/src/disk.h
@@ -64,7 +64,8 @@ disk_write_latch(void),
 disk_read_prepare_in(void),
 disk_read_prepare_out(void);
 
-#ifdef TESTING
+#if DISK_TRACING
+void c_toggle_disk_trace_6(const char *read_file, const char *write_file);
 void c_begin_disk_trace_6(const char *read_file, const char *write_file);
 void c_end_disk_trace_6(void);
 #endif
diff --git a/src/meta/debug.l b/src/meta/debug.l
index 8b2ed8cf..c3c2e46e 100644
--- a/src/meta/debug.l
+++ b/src/meta/debug.l
@@ -861,6 +861,17 @@ ADDRS	[0-9a-fA-F]+
 #endif
 }
 
+{BOS}diskt?r?a?c?e?{EOS} {
+#if DISK_TRACING
+    char *buf = NULL;
+    asprintf(&buf, "%s/%s", getenv("HOME"), "disktrace.txt");
+    c_toggle_disk_trace_6(buf, NULL);
+    free(buf);
+#else
+    LOG("CPU tracing not enabled...");
+#endif
+}
+
 {BOS}la?n?g?{EOS} {
     /* display language card settings */
     show_lc_info();
diff --git a/src/test/testvm.c b/src/test/testvm.c
index 38548a85..c1525245 100644
--- a/src/test/testvm.c
+++ b/src/test/testvm.c
@@ -60,12 +60,12 @@ static void sha1_to_str(const uint8_t * const md, char *buf) {
 // ----------------------------------------------------------------------------
 // VM TESTS ...
 
-#define EXPECTED_DISK_TRACE_FILE_SIZE 60961
-#define EXPECTED_DISK_TRACE_SHA "D21CC686571ADE868A909B5A7044A973DE70DFFB"
+#define EXPECTED_DISK_TRACE_FILE_SIZE 128794
+#define EXPECTED_DISK_TRACE_SHA "7CEBB3690E66605E558D98D9041C29AE10C92D42"
 TEST test_boot_disk_bytes() {
     char *homedir = getenv("HOME");
     char *disk = NULL;
-    asprintf(&disk, "%s/a2_read_disk_test.raw", homedir);
+    asprintf(&disk, "%s/a2_read_disk_test.txt", homedir);
     if (disk) {
         unlink(disk);
         c_begin_disk_trace_6(disk, NULL);