diff --git a/autd3-firmware-emulator/src/fpga/emulator/modulation.rs b/autd3-firmware-emulator/src/fpga/emulator/modulation.rs
index f3860355..55db1f15 100644
--- a/autd3-firmware-emulator/src/fpga/emulator/modulation.rs
+++ b/autd3-firmware-emulator/src/fpga/emulator/modulation.rs
@@ -56,9 +56,13 @@ impl FPGAEmulator {
     }
 
     pub fn modulation_buffer(&self, segment: Segment) -> Vec<u8> {
-        (0..self.modulation_cycle(segment))
-            .map(|i| self.modulation_at(segment, i))
-            .collect()
+        let mut dst = vec![0; self.modulation_cycle(segment)];
+        self.modulation_buffer_inplace(segment, &mut dst);
+        dst
+    }
+
+    pub fn modulation_buffer_inplace(&self, segment: Segment, dst: &mut [u8]) {
+        (0..self.modulation_cycle(segment)).for_each(|i| dst[i] = self.modulation_at(segment, i));
     }
 
     pub fn modulation_transition_mode(&self) -> TransitionMode {
diff --git a/autd3-firmware-emulator/src/fpga/emulator/pwe.rs b/autd3-firmware-emulator/src/fpga/emulator/pwe.rs
index 1899c22d..1f525cfe 100644
--- a/autd3-firmware-emulator/src/fpga/emulator/pwe.rs
+++ b/autd3-firmware-emulator/src/fpga/emulator/pwe.rs
@@ -10,11 +10,18 @@ impl FPGAEmulator {
     }
 
     pub fn pulse_width_encoder_table(&self) -> Vec<u8> {
+        let mut dst = vec![0; 256];
+        self.pulse_width_encoder_table_inplace(&mut dst);
+        dst
+    }
+
+    pub fn pulse_width_encoder_table_inplace(&self, dst: &mut [u8]) {
         self.mem
             .duty_table_bram()
             .iter()
             .flat_map(|&d| vec![(d & 0xFF) as u8, (d >> 8) as u8])
-            .collect()
+            .enumerate()
+            .for_each(|(i, v)| dst[i] = v);
     }
 
     pub fn to_pulse_width(&self, a: EmitIntensity, b: u8) -> u8 {
diff --git a/autd3-firmware-emulator/src/fpga/emulator/stm/foci.rs b/autd3-firmware-emulator/src/fpga/emulator/stm/foci.rs
index 5755e28f..e2259474 100644
--- a/autd3-firmware-emulator/src/fpga/emulator/stm/foci.rs
+++ b/autd3-firmware-emulator/src/fpga/emulator/stm/foci.rs
@@ -23,7 +23,7 @@ impl FPGAEmulator {
         }] as u8
     }
 
-    pub(crate) fn foci_stm_drives(&self, segment: Segment, idx: usize) -> Vec<Drive> {
+    pub(crate) fn foci_stm_drives_inplace(&self, segment: Segment, idx: usize, dst: &mut [Drive]) {
         let bram = match segment {
             Segment::S0 => self.mem.stm_bram_0(),
             Segment::S1 => self.mem.stm_bram_1(),
@@ -35,7 +35,8 @@ impl FPGAEmulator {
             .tr_pos
             .iter()
             .take(self.mem.num_transducers)
-            .map(|&tr| {
+            .enumerate()
+            .for_each(|(i, &tr)| {
                 let tr_z = ((tr >> 32) & 0xFFFF) as i16 as i32;
                 let tr_x = ((tr >> 16) & 0xFFFF) as i16 as i32;
                 let tr_y = (tr & 0xFFFF) as i16 as i32;
@@ -68,9 +69,8 @@ impl FPGAEmulator {
                 let sin = ((sin / self.num_foci(segment) as u16) >> 1) as usize;
                 let cos = ((cos / self.num_foci(segment) as u16) >> 1) as usize;
                 let phase = self.mem.atan_table[(sin << 7) | cos];
-                Drive::new(Phase::new(phase), EmitIntensity::new(intensity))
-            })
-            .collect()
+                dst[i] = Drive::new(Phase::new(phase), EmitIntensity::new(intensity));
+            });
     }
 
     pub fn local_tr_pos(&self) -> &[u64] {
diff --git a/autd3-firmware-emulator/src/fpga/emulator/stm/gain.rs b/autd3-firmware-emulator/src/fpga/emulator/stm/gain.rs
index 54ab5fad..3982ec1f 100644
--- a/autd3-firmware-emulator/src/fpga/emulator/stm/gain.rs
+++ b/autd3-firmware-emulator/src/fpga/emulator/stm/gain.rs
@@ -6,7 +6,7 @@ use autd3_driver::{
 use crate::FPGAEmulator;
 
 impl FPGAEmulator {
-    pub(crate) fn gain_stm_drives(&self, segment: Segment, idx: usize) -> Vec<Drive> {
+    pub(crate) fn gain_stm_drives_inplace(&self, segment: Segment, idx: usize, dst: &mut [Drive]) {
         match segment {
             Segment::S0 => self.mem.stm_bram_0(),
             Segment::S1 => self.mem.stm_bram_1(),
@@ -15,12 +15,12 @@ impl FPGAEmulator {
         .iter()
         .skip(256 * idx)
         .take(self.mem.num_transducers)
-        .map(|&d| {
-            Drive::new(
+        .enumerate()
+        .for_each(|(i, &d)| {
+            dst[i] = Drive::new(
                 Phase::new((d & 0xFF) as u8),
                 EmitIntensity::new(((d >> 8) & 0xFF) as u8),
             )
         })
-        .collect()
     }
 }
diff --git a/autd3-firmware-emulator/src/fpga/emulator/stm/mod.rs b/autd3-firmware-emulator/src/fpga/emulator/stm/mod.rs
index 8eb9a6f6..84189373 100644
--- a/autd3-firmware-emulator/src/fpga/emulator/stm/mod.rs
+++ b/autd3-firmware-emulator/src/fpga/emulator/stm/mod.rs
@@ -93,10 +93,16 @@ impl FPGAEmulator {
     }
 
     pub fn drives_at(&self, segment: Segment, idx: usize) -> Vec<Drive> {
+        let mut dst = vec![Drive::null(); self.mem.num_transducers];
+        self.drives_at_inplace(segment, idx, &mut dst);
+        dst
+    }
+
+    pub fn drives_at_inplace(&self, segment: Segment, idx: usize, dst: &mut [Drive]) {
         if self.is_stm_gain_mode(segment) {
-            self.gain_stm_drives(segment, idx)
+            self.gain_stm_drives_inplace(segment, idx, dst)
         } else {
-            self.foci_stm_drives(segment, idx)
+            self.foci_stm_drives_inplace(segment, idx, dst)
         }
     }
 }