diff --git a/crates/coremem/src/driver.rs b/crates/coremem/src/driver.rs
index d6b4e33..e0e72da 100644
--- a/crates/coremem/src/driver.rs
+++ b/crates/coremem/src/driver.rs
@@ -296,14 +296,8 @@ where
         }
         steps_this_time
     }
-    pub fn step_multiple(&mut self, num_steps: u32) {
-        let mut steps_remaining = num_steps;
-        while steps_remaining != 0 {
-            steps_remaining -= self.step_at_most(steps_remaining);
-        }
-    }
     pub fn step(&mut self) {
-        self.step_multiple(1);
+        self.step_at_most(1);
     }
 
     /// Returns the number of timesteps needed to reach the end time
@@ -318,7 +312,9 @@ where
         self.sim_end_time = Some(sim_end_time);
         let mut stepped = false;
         while self.state.step_no() < *sim_end_time {
-            self.step_multiple(1000);
+            let steps_left = *sim_end_time - self.state.step_no();
+            // sanity limit: don't try to step too much at once else we may lock up the GPU/etc.
+            self.step_at_most(steps_left.min(1000) as u32);
             stepped = true;
         }
         if stepped {
@@ -519,9 +515,11 @@ impl<R: Real, T: DriverStimulus<R> + Send + 'static> StimAccess<R, T> {
         assert!(!self.outstanding.get());
         self.outstanding.set(true);
 
+        // these are cheap Arc clones
         let diag = self.diag.clone();
         let stim = self.stim.clone();
         let response_handle = self.response_channel.0.clone();
+
         self.worker.execute(move || {
             trace!("eval_stimulus begin");
             let rendered = diag.instrument_stimuli(|| {