diff --git a/artiq/runtime.rs/libksupport/api.rs b/artiq/runtime.rs/libksupport/api.rs
index dbfbd759b..57b6302d8 100644
--- a/artiq/runtime.rs/libksupport/api.rs
+++ b/artiq/runtime.rs/libksupport/api.rs
@@ -102,6 +102,7 @@ static mut API: &'static [(&'static str, *const ())] = &[
     api!(rtio_get_counter = ::rtio::get_counter),
     api!(rtio_log),
     api!(rtio_output = ::rtio::output),
+    api!(rtio_output_list = ::rtio::output_list),
     api!(rtio_input_timestamp = ::rtio::input_timestamp),
     api!(rtio_input_data = ::rtio::input_data),
 
diff --git a/artiq/runtime.rs/libksupport/rtio.rs b/artiq/runtime.rs/libksupport/rtio.rs
index 4363b255d..eaeb4d01c 100644
--- a/artiq/runtime.rs/libksupport/rtio.rs
+++ b/artiq/runtime.rs/libksupport/rtio.rs
@@ -1,4 +1,6 @@
 use board::csr;
+use core::ptr::{read_volatile, write_volatile};
+use core::slice;
 
 const RTIO_O_STATUS_FULL:           u32 = 1;
 const RTIO_O_STATUS_UNDERFLOW:      u32 = 2;
@@ -23,6 +25,21 @@ pub extern fn get_counter() -> i64 {
     }
 }
 
+#[inline(always)]
+pub unsafe fn rtio_o_data_write(w: u32) {
+    write_volatile(
+        csr::rtio::O_DATA_ADDR.offset((csr::rtio::O_DATA_SIZE - 1) as isize),
+        w);
+}
+
+#[inline(always)]
+pub unsafe fn rtio_i_data_read() -> u32 {
+    read_volatile(
+        csr::rtio::I_DATA_ADDR.offset((csr::rtio::I_DATA_SIZE - 1) as isize)
+        )
+}
+
+
 #[inline(never)]
 unsafe fn process_exceptional_status(timestamp: i64, channel: u32, status: u32) {
     if status & RTIO_O_STATUS_FULL != 0 {
@@ -59,7 +76,27 @@ pub extern fn output(timestamp: i64, channel: u32, addr: u32, data: u32) {
         csr::rtio::chan_sel_write(channel);
         csr::rtio::o_timestamp_write(timestamp as u64);
         csr::rtio::o_address_write(addr);
-        csr::rtio::o_data_write(data);
+        rtio_o_data_write(data);
+        csr::rtio::o_we_write(1);
+        let status = csr::rtio::o_status_read();
+        if status != 0 {
+            process_exceptional_status(timestamp, channel, status);
+        }
+    }
+}
+
+pub extern fn output_list(timestamp: i64, channel: u32, addr: u32,
+                          &(len, ptr): &(usize, *const u32)) {
+    unsafe {
+        csr::rtio::chan_sel_write(channel);
+        csr::rtio::o_timestamp_write(timestamp as u64);
+        csr::rtio::o_address_write(addr);
+        let data = slice::from_raw_parts(ptr, len);
+        for i in 0..data.len() {
+            write_volatile(
+                csr::rtio::O_DATA_ADDR.offset((csr::rtio::O_DATA_SIZE - 1 - i) as isize),
+                data[i]);
+        }
         csr::rtio::o_we_write(1);
         let status = csr::rtio::o_status_read();
         if status != 0 {
@@ -119,7 +156,7 @@ pub extern fn input_data(channel: u32) -> u32 {
             }
         }
 
-        let data = csr::rtio::i_data_read();
+        let data = rtio_i_data_read();
         csr::rtio::i_re_write(1);
         data
     }
@@ -136,14 +173,14 @@ pub fn log(timestamp: i64, data: &[u8]) {
             word <<= 8;
             word |= data[i] as u32;
             if i % 4 == 0 {
-                csr::rtio::o_data_write(word);
+                rtio_o_data_write(word);
                 csr::rtio::o_we_write(1);
                 word = 0;
             }
         }
 
         word <<= 8;
-        csr::rtio::o_data_write(word);
+        rtio_o_data_write(word);
         csr::rtio::o_we_write(1);
     }
 }