diff --git a/src/disk/mo.c b/src/disk/mo.c
index c039695b5..f1cd3b983 100644
--- a/src/disk/mo.c
+++ b/src/disk/mo.c
@@ -486,19 +486,16 @@ mo_bus_speed(mo_t *dev)
 {
     double ret = -1.0;
 
-    if (dev && dev->drv && (dev->drv->bus_type == MO_BUS_SCSI)) {
-        dev->callback = -1.0; /* Speed depends on SCSI controller */
-        return 0.0;
-    } else {
-        if (dev && dev->drv)
-            ret = ide_atapi_get_period(dev->drv->ide_channel);
-        if (ret == -1.0) {
-            if (dev)
-                dev->callback = -1.0;
-            return 0.0;
-        } else
-            return ret * 1000000.0;
+    if (dev && dev->drv)
+        ret = ide_atapi_get_period(dev->drv->ide_channel);
+
+    if (ret == -1.0) {
+        if (dev)
+            dev->callback = -1.0;
+        ret = 0.0;
     }
+
+    return ret;
 }
 
 static void
@@ -509,18 +506,10 @@ mo_command_common(mo_t *dev)
     dev->tf->pos    = 0;
     if (dev->packet_status == PHASE_COMPLETE)
         dev->callback = 0.0;
-    else {
-        double bytes_per_second;
-
-        if (dev->drv->bus_type == MO_BUS_SCSI) {
-            dev->callback = -1.0; /* Speed depends on SCSI controller */
-            return;
-        } else
-            bytes_per_second = mo_bus_speed(dev);
-
-        const double period = 1000000.0 / bytes_per_second;
-        dev->callback       = period * (double) (dev->packet_len);
-    }
+    else if (dev->drv->bus_type == MO_BUS_SCSI)
+        dev->callback = -1.0; /* Speed depends on SCSI controller */
+    else
+        dev->callback = mo_bus_speed(dev) * (double) (dev->packet_len);
 
     mo_set_callback(dev);
 }
diff --git a/src/disk/zip.c b/src/disk/zip.c
index ed59154b0..eecafb802 100644
--- a/src/disk/zip.c
+++ b/src/disk/zip.c
@@ -567,19 +567,16 @@ zip_bus_speed(zip_t *dev)
 {
     double ret = -1.0;
 
-    if (dev && dev->drv && (dev->drv->bus_type == ZIP_BUS_SCSI)) {
-        dev->callback = -1.0; /* Speed depends on SCSI controller */
-        return 0.0;
-    } else {
-        if (dev && dev->drv)
-            ret = ide_atapi_get_period(dev->drv->ide_channel);
-        if (ret == -1.0) {
-            if (dev)
-                dev->callback = -1.0;
-            return 0.0;
-        } else
-            return ret * 1000000.0;
+    if (dev && dev->drv)
+        ret = ide_atapi_get_period(dev->drv->ide_channel);
+
+    if (ret == -1.0) {
+        if (dev)
+            dev->callback = -1.0;
+        ret = 0.0;
     }
+
+    return ret;
 }
 
 static void
@@ -590,18 +587,10 @@ zip_command_common(zip_t *dev)
     dev->tf->pos    = 0;
     if (dev->packet_status == PHASE_COMPLETE)
         dev->callback = 0.0;
-    else {
-        double bytes_per_second;
-
-        if (dev->drv->bus_type == ZIP_BUS_SCSI) {
-            dev->callback = -1.0; /* Speed depends on SCSI controller */
-            return;
-        } else
-            bytes_per_second = zip_bus_speed(dev);
-
-        double period        = 1000000.0 / bytes_per_second;
-        dev->callback        = period * (double) (dev->packet_len);
-    }
+    else if (dev->drv->bus_type == ZIP_BUS_SCSI)
+        dev->callback = -1.0; /* Speed depends on SCSI controller */
+    else
+        dev->callback = zip_bus_speed(dev) * (double) (dev->packet_len);
 
     zip_set_callback(dev);
 }
diff --git a/src/scsi/scsi_cdrom.c b/src/scsi/scsi_cdrom.c
index b35662eeb..9ae65be74 100644
--- a/src/scsi/scsi_cdrom.c
+++ b/src/scsi/scsi_cdrom.c
@@ -656,7 +656,7 @@ scsi_cdrom_bus_speed(scsi_cdrom_t *dev)
                 dev->callback = -1.0;
             return 0.0;
         } else
-            return ret * 1000000.0;
+            return 1000000.0 / ret;
     }
 }
 
@@ -1069,8 +1069,9 @@ scsi_cdrom_read_data(scsi_cdrom_t *dev, const int msf, const int type, const int
                     dev->block_len = temp_len;
 
                     if ((dev->drv->bus_type != CDROM_BUS_SCSI) &&
-                        (scsi_cdrom_current_mode(dev) != 2))
+                        (scsi_cdrom_current_mode(dev) != 2)) {
                         num = (dev->packet_len / dev->block_len);
+                    }
                 }
 
                 dev->sector_pos++;
@@ -1126,7 +1127,7 @@ scsi_cdrom_read_blocks(scsi_cdrom_t *dev)
     }
 
     if (ret) {
-        if (!dev->sector_len) {
+        if (dev->sector_len == 0) {
             scsi_cdrom_command_complete(dev);
             return -1;
         }
diff --git a/src/scsi/scsi_disk.c b/src/scsi/scsi_disk.c
index a1afca2e2..8528db1fb 100644
--- a/src/scsi/scsi_disk.c
+++ b/src/scsi/scsi_disk.c
@@ -400,7 +400,8 @@ scsi_disk_bus_speed(scsi_disk_t *dev)
                 dev->callback = -1.0;
             return 0.0;
         } else
-            return ret * 1000000.0;
+            /* We get bytes per µs, so divide 1000000.0 by it. */
+            return 1000000.0 / ret;
     }
 }
 
@@ -484,6 +485,10 @@ scsi_disk_command_common(scsi_disk_t *dev)
                 break;
         }
 
+        /*
+           For ATAPI, this will be 1000000.0 / µs_per_byte, and this will
+           convert it back to µs_per_byte.
+         */
         period = 1000000.0 / bytes_per_second;
         scsi_disk_log(dev->log, "Byte transfer period: %" PRIu64 " us\n",
                       (uint64_t) period);