diff --git a/src/m_default/_default.c b/src/m_default/_default.c
index 591171e..b9cbbe7 100644
--- a/src/m_default/_default.c
+++ b/src/m_default/_default.c
@@ -3,6 +3,7 @@
 #include <tusb.h>
 
 #include "mode.h"
+#include "storage.h"
 #include "thread.h"
 #include "usbstdio.h"
 #include "vnd_cfg.h"
@@ -35,6 +36,8 @@ enum m_default_feature {
     mdef_feat_tempsense = 1<<4,
 };
 
+static bool data_dirty = false;
+
 #ifdef DBOARD_HAS_UART
 static cothread_t uartthread;
 static uint8_t    uartstack[THREAD_STACK_SIZE];
@@ -81,6 +84,17 @@ static void enter_cb(void) {
     serprogthread = co_derive(serprogstack, sizeof serprogstack, serprog_thread_fn);
     thread_enter(serprogthread);  // will call cdc_serprog_init() on correct thread
 #endif
+
+    if (!data_dirty) { // only read when not read yet
+        struct mode_info mi = storage_mode_get_info(1);
+        if (mi.size != 0 && mi.version == 0x0010 /* TODO: version migration? */) {
+            uint8_t dst[2];
+            storage_mode_read(1, dst, 0, 2);
+
+            cdc_uart_set_hwflow(dst[0]);
+            tempsense_set_addr(dst[1]);
+        }
+    }
 }
 static void leave_cb(void) {
     // TODO: CMSISDAP?
@@ -144,7 +158,12 @@ static void handle_cmd_cb(uint8_t cmd) {
         break;
     case mdef_cmd_tempsense:
 #ifdef DBOARD_HAS_TEMPSENSOR
-        tempsense_bulk_cmd();
+        {
+            uint8_t addra = tempsense_get_addr();
+            tempsense_bulk_cmd();
+            uint8_t addrb = tempsense_get_addr();
+            data_dirty |= addra != addrb;
+        }
 #else
         vnd_cfg_write_str(cfg_resp_illcmd, "temperature sensor not implemented on this device");
 #endif
@@ -156,9 +175,10 @@ static void handle_cmd_cb(uint8_t cmd) {
             resp = cdc_uart_get_hwflow() ? 1 : 0;
             vnd_cfg_write_resp(cfg_resp_ok, 1, &resp);
         } else {
-            if (cdc_uart_set_hwflow(resp != 0))
+            if (cdc_uart_set_hwflow(resp != 0)) {
                 vnd_cfg_write_resp(cfg_resp_ok, 0, NULL);
-            else
+                data_dirty = true;
+            } else
                 vnd_cfg_write_str(cfg_resp_illcmd, "UART flow control setting not supported on this device");
         }
 #else
@@ -387,6 +407,19 @@ static bool my_vendor_control_xfer_cb(uint8_t rhport, uint8_t ep_addr,
 }
 #endif
 
+static uint16_t my_get_size(void) { return 2; }
+static void my_get_data(void* dst, size_t offset, size_t maxsize) {
+    (void)offset; (void)maxsize;
+
+    uint8_t* d = dst;
+
+    d[0] = cdc_uart_get_hwflow() ? 1 : 0;
+    d[1] = tempsense_get_addr();
+
+    data_dirty = false;
+}
+static bool my_is_dirty(void) { return data_dirty; }
+
 extern struct mode m_01_default;
 // clang-format off
 struct mode m_01_default = {
@@ -402,6 +435,13 @@ struct mode m_01_default = {
     .task  = task_cb,
     .handle_cmd = handle_cmd_cb,
 
+    .storage = {
+        .stclass = mode_storage_32b,
+        .get_size = my_get_size,
+        .get_data = my_get_data,
+        .is_dirty = my_is_dirty
+    },
+
 #if defined(DBOARD_HAS_CMSISDAP) && CFG_TUD_HID > 0
 #if 0
     .tud_hid_get_report_cb = my_hid_get_report_cb,
diff --git a/src/m_sump/_sump.c b/src/m_sump/_sump.c
index 4e2cb82..da3e1e2 100644
--- a/src/m_sump/_sump.c
+++ b/src/m_sump/_sump.c
@@ -3,6 +3,7 @@
 #include <tusb.h>
 
 #include "mode.h"
+#include "storage.h"
 #include "thread.h"
 #include "usbstdio.h"
 #include "vnd_cfg.h"
@@ -20,6 +21,8 @@ enum m_sump_feature {
     msump_feat_sump      = 1<<0,
 };
 
+static bool data_dirty = false;
+
 #ifdef DBOARD_HAS_SUMP
 static cothread_t sumpthread;
 static uint8_t    sumpstack[THREAD_STACK_SIZE];
@@ -44,6 +47,16 @@ static void enter_cb(void) {
     sumpthread = co_derive(sumpstack, sizeof sumpstack, sump_thread_fn);
     thread_enter(sumpthread);
 #endif
+
+    if (!data_dirty) { // only read when not read yet
+        struct mode_info mi = storage_mode_get_info(4);
+        if (mi.size != 0 && mi.version == 0x0010 /* TODO: version migration? */) {
+            uint8_t dst[1];
+            storage_mode_read(4, dst, 0, 1);
+
+            sump_hw_set_overclock(dst[0]);
+        }
+    }
 }
 static void leave_cb(void) {
 #ifdef DBOARD_HAS_SUMP
@@ -133,7 +146,6 @@ enum {
 #define EPNUM_CDC_STDIO_NOTIF   0x85
 
 // clang-format off
-// TODO: replace magic 64s by actual buffer size macros
 static const uint8_t desc_configuration[] = {
     TUD_CONFIG_DESCRIPTOR(1, ITF_NUM__TOTAL, STRID_CONFIG, CONFIG_TOTAL_LEN,
         TUSB_DESC_CONFIG_ATT_REMOTE_WAKEUP, 100),
@@ -178,6 +190,17 @@ static void my_cdc_line_coding_cb(uint8_t itf, cdc_line_coding_t const* line_cod
 }
 #endif
 
+static uint16_t my_get_size(void) { return 1; }
+static void my_get_data(void* dst, size_t offset, size_t maxsize) {
+    (void)offset; (void)maxsize;
+
+    uint8_t* d = dst;
+    d[0] = sump_hw_get_overclock();
+
+    data_dirty = false;
+}
+static bool my_is_dirty(void) { return data_dirty; }
+
 extern struct mode m_04_sump;
 // clang-format off
 struct mode m_04_sump = {
@@ -188,6 +211,13 @@ struct mode m_04_sump = {
     .usb_desc = desc_configuration,
     .string_desc = string_desc_arr,
 
+    .storage = {
+        .stclass = mode_storage_32b,
+        .get_size = my_get_size,
+        .get_data = my_get_data,
+        .is_dirty = my_is_dirty
+    },
+
     .enter = enter_cb,
     .leave = leave_cb,
     .task  = task_cb,
diff --git a/src/storage.c b/src/storage.c
index a253d39..ff1c11d 100644
--- a/src/storage.c
+++ b/src/storage.c
@@ -6,14 +6,14 @@
 #include "storage.h"
 
 #if !defined(PERSISTENT_STORAGE) || !defined(DBOARD_HAS_STORAGE)
-/*int storage_init(void) { return -1; }
+int storage_init(void) { return -1; }
 bool storage_flush_data(void) { return false; }
-struct mode_info storage_mode_get_size(int _) {
+struct mode_info storage_mode_get_info(int _) {
     (void)_; return (struct mode_info){ .size = 0, .version = 0 };
 }
 void storage_mode_read(int _, void* __, size_t ___, size_t ____) {
     (void)_; (void)__; (void)___; (void)____;
-}*/
+}
 #else
 
 #include "storage_internal.h"
diff --git a/src/storage.h b/src/storage.h
index 25c4b6a..b5bfb06 100644
--- a/src/storage.h
+++ b/src/storage.h
@@ -20,6 +20,7 @@ enum mode_storage_class {
 struct mode_storage {
     enum mode_storage_class stclass;
     uint16_t (*get_size)(void);
+    // if stclass < 512b, offset & maxsize can be ignored
     void     (*get_data)(void* dst, size_t offset, size_t maxsize);
     bool     (*is_dirty)(void); // if data was changed since last mode_read/get_data call
 };
diff --git a/src/storage_save.c b/src/storage_save.c
index 771581b..45956bb 100644
--- a/src/storage_save.c
+++ b/src/storage_save.c
@@ -48,7 +48,7 @@ static size_t storage_allocate_new(void) {
             uint16_t dsize = mode_list[mode]->storage.get_size();
             if (dsize > stclass_sz[stcls]) continue;
 
-            if (current_wrhead + dsize > current_page_end) { // welp
+            if (current_wrhead + dsize > current_page_end) { // FIXME: data that is >1 page size (do we want to support this?)
                 current_page_end = current_page;
                 current_page -= STORAGE_ERASEWRITE_ALIGN;
                 current_wrhead = current_page;