diff --git a/stm32/COLDCARD_MK4/file_time.c b/stm32/COLDCARD_MK4/file_time.c
index 59c5abfb..1ae75450 100644
--- a/stm32/COLDCARD_MK4/file_time.c
+++ b/stm32/COLDCARD_MK4/file_time.c
@@ -2,12 +2,12 @@
 //
 // AUTO-generated.
 //
-//   built: 2024-03-10
-// version: 1.0.0Q
+//   built: 2024-04-11
+// version: 5.3.0
 //
 #include <stdint.h>
 
 // this overrides ports/stm32/fatfs_port.c
 uint32_t get_fattime(void) {
-    return 0x586a0800UL;
+    return 0x588b2860UL;
 }
diff --git a/stm32/COLDCARD_MK4/psramdisk.c b/stm32/COLDCARD_MK4/psramdisk.c
index 813f7efb..b1fc0d69 100644
--- a/stm32/COLDCARD_MK4/psramdisk.c
+++ b/stm32/COLDCARD_MK4/psramdisk.c
@@ -499,13 +499,30 @@ static void psram_init_vfs(fs_user_mount_t *vfs, bool readonly) {
     vfs->blockdev.u.ioctl[1] = MP_OBJ_FROM_PTR(&psram_obj);
 }
 
+// psram_memset4()
+//
+    static inline void
+psram_memset4(void *dest_addr, uint32_t value, uint32_t byte_len)
+{
+    // Fast, aligned, and bug-fixing memset
+    // - PSRAM can starve the internal bus with too many writes, too fast
+    // - leads to a weird crash where SRAM bus (at least) is locked up, but flash works
+    uint32_t *dest = (uint32_t *)dest_addr;
+
+    for(; byte_len; byte_len-=4, dest++) {
+        *dest = value;
+
+        asm("nop; nop; nop;");           // tested value, do not reduce
+    }
+}
+
 mp_obj_t psram_wipe_and_setup(mp_obj_t unused_self)
 {
     // Erase and reformat filesystem
     //  - you probably should unmount it, before calling this 
 
     // Wipe contents for security.
-    memset(PSRAM_TOP_BASE, 0x21, BLOCK_SIZE * BLOCK_COUNT);
+    psram_memset4(PSRAM_TOP_BASE, 0x12345678, BLOCK_SIZE * BLOCK_COUNT);
 
     // Build obj to handle blockdev protocol
     fs_user_mount_t vfs = {0};