diff --git a/remotesyn/toolchains/iverilog.py b/remotesyn/toolchains/iverilog.py
new file mode 100644
index 0000000..f12dad5
--- /dev/null
+++ b/remotesyn/toolchains/iverilog.py
@@ -0,0 +1,122 @@
+# iverilog.py
+import shutil
+import os
+import time
+import subprocess
+
+def _execp(cmd, subprocesses, cwd):
+    p = subprocess.Popen(
+        cmd,
+        shell=True,
+        cwd=cwd,
+        stdin=subprocess.DEVNULL,
+        # stdout/stderr visible so tee can capture; keep quiet if you prefer:
+        # stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL
+    )
+    subprocesses.append(p)
+    while p.poll() is None:
+        time.sleep(0.2)
+    return p.returncode
+
+def do(config, target, log, subprocesses, prefix='.'):
+    # fresh build dir
+    shutil.rmtree(config.get('project', 'build_dir', fallback='build'), True)
+
+    log("Starting simulation (iverilog)")
+
+    # --- parse options (keep names consistent with your other toolchains) ---
+    toplevel        = config.get(f'target.{target}', 'toplevel',       fallback='toplevel')
+    ivl_opts        = config.get(f'target.{target}', 'ivl_opts',       fallback='')
+    vvp_opts        = config.get(f'target.{target}', 'vvp_opts',       fallback='')
+    runtime         = config.get(f'target.{target}', 'runtime',        fallback='')  # optional; TB can honor +stop_time
+    files_verilog   = config.get(f'target.{target}', 'files_verilog',  fallback='').split()
+    files_sysverilog= config.get(f'target.{target}', 'files_sysverilog', fallback='').split()
+    files_vhdl      = config.get(f'target.{target}', 'files_vhdl',     fallback='').split()
+    files_other     = config.get(f'target.{target}', 'files_other',    fallback='').split()
+    build_dir       = config.get('project', 'build_dir',               fallback='build')
+    out_dir_root    = config.get('project', 'out_dir',                 fallback='out')
+
+    # normalize paths
+    prefix   = f'{os.getcwd()}/{prefix}'
+    build_dir= f'{prefix}/{build_dir}'
+    out_dir  = f'{prefix}/{out_dir_root}/{target}'
+
+    # minor sanitization
+    ivl_opts = ivl_opts.replace('\n', ' ')
+    vvp_opts = vvp_opts.replace('\n', ' ')
+
+    # --- create dirs ---
+    log(" - creating output directories")
+    os.makedirs(build_dir, exist_ok=True)
+    os.makedirs(out_dir, exist_ok=True)
+
+    # --- copy extra needed files into build dir (keeping tree) ---
+    if files_other:
+        log(" - copy needed files")
+    for f in files_other:
+        if not f: continue
+        d = os.path.dirname(f)
+        if d:
+            os.makedirs(f"{build_dir}/{d}", exist_ok=True)
+        shutil.copy(f"{prefix}/{f}", f"{build_dir}/{f}")
+
+    # --- guard: VHDL not supported by Icarus ---
+    if any(s for s in files_vhdl if s.strip()):
+        log("WARNING: VHDL files listed but iverilog does not support VHDL — ignoring them")
+
+    # --- build source list (order as provided) ---
+    sources = []
+    for s in files_verilog:
+        if s: sources.append(f'"{prefix}/{s}"')
+    for s in files_sysverilog:
+        if s: sources.append(f'"{prefix}/{s}"')
+
+    if not sources:
+        log("ERROR: no Verilog/SystemVerilog sources provided")
+        return 1
+
+    # --- decide standard (enable SV if any sysverilog files or if user asked) ---
+    needs_sv = len([1 for _ in files_sysverilog if _]) > 0
+    std_flag = "-g2012" if needs_sv and "-g" not in ivl_opts and "-g2012" not in ivl_opts else ""
+
+    # --- compile ---
+    log(" - compile (iverilog)")
+    # -s <top> sets the toplevel; produce sim.vvp; tee compile log
+    # You can add include dirs/defines via ivl_opts (e.g., -Iinc -DNAME=VALUE)
+    cmd_compile = f'iverilog -o sim.vvp -s {toplevel} {std_flag} {ivl_opts} ' + " ".join(sources) + ' 2>&1 | tee comp.log'
+    res = _execp(cmd_compile, subprocesses, build_dir)
+
+    # logs
+    shutil.copy(f'{build_dir}/comp.log', f'{out_dir}/compile.log')
+    if res != 0:
+        log("ERROR: iverilog returned with", res)
+        return res
+
+    # --- simulate ---
+    log(" - simulate (vvp)")
+    # If your TB supports +stop_time=<time>, we pass it from 'runtime' (e.g., "1000us" -> +stop_time=1000us)
+    plusargs = []
+    if runtime and runtime.strip().lower() != 'all':
+        rt = runtime.replace(" ", "")
+        plusargs.append(f'+stop_time={rt}')   # your TB can $value$plusargs("stop_time=%s", str)
+
+    cmd_run = f'vvp {vvp_opts} sim.vvp ' + " ".join(plusargs) + ' 2>&1 | tee sim.log'
+    res = _execp(cmd_run, subprocesses, build_dir)
+
+    # copy sim log
+    shutil.copy(f'{build_dir}/sim.log', f'{out_dir}/simulate.log')
+
+    # --- copy outputs if present ---
+    # Expect the TB to do $dumpfile("out.vcd"); $dumpvars; (or use your own filename)
+    vcd_candidates = ["out.vcd", f"{toplevel}.vcd", "sim.vcd"]
+    copied = False
+    for vcd in vcd_candidates:
+        src = f'{build_dir}/{vcd}'
+        if os.path.exists(src):
+            shutil.copy(src, f'{out_dir}/out.vcd')
+            copied = True
+            break
+    if not copied:
+        log("NOTE: no VCD found (ensure your TB calls $dumpfile(\"out.vcd\") and $dumpvars)")
+
+    return res
diff --git a/remotesyn/toolchains/util_ISE/xst.py b/remotesyn/toolchains/util_ISE/xst.py
index 9447ceb..613c36e 100644
--- a/remotesyn/toolchains/util_ISE/xst.py
+++ b/remotesyn/toolchains/util_ISE/xst.py
@@ -14,6 +14,7 @@ def xst(config, target, log, subprocesses, prefix='.') -> int:
     netgensynth_type = config.get(f'target.{target}', 'netgensynth_type', fallback='-sim')
     files_vhdl = config.get(f'target.{target}', 'files_vhdl', fallback='').split()
     files_verilog = config.get(f'target.{target}', 'files_verilog', fallback='').split()
+    files_other = config.get(f'target.{target}', 'files_other', fallback='').split()
     build_dir = config.get(f'project', 'build_dir', fallback='build')
     out_dir = config.get(f'project', 'out_dir', fallback='out')
 
@@ -36,16 +37,23 @@ def xst(config, target, log, subprocesses, prefix='.') -> int:
             if s=='':
                 continue
             f.write(f"verilog work {prefix}/{s}\n")
+    for f in files_other:
+        if not f: continue
+        d = os.path.dirname(f)
+        if d:
+            os.makedirs(f"{build_dir}/{d}", exist_ok=True)
+        shutil.copy(f"{prefix}/{f}", f"{build_dir}/{f}")
 
     log(" - writing project generation file")
     with open(f'{build_dir}/prj.scr', 'w') as f:
         f.write(f'run\n-ifn syn.prj\n-ofn syn.ngc\n-ifmt mixed\n')
         f.write(f'-top {toplevel}\n')
         f.write(f'-p {devstring}\n-glob_opt max_delay -opt_mode speed\n')
-        f.write(f'-read_cores YES')
+        f.write(xst_opts)
+        f.write(f'\n-read_cores YES')
 
     log(" - run xst")
-    p = subprocess.Popen(f"xst -intstyle xflow {xst_opts} -ifn prj.scr", 
+    p = subprocess.Popen(f"xst -intstyle xflow -ifn prj.scr", 
         shell=True, cwd=build_dir, 
         stdin=subprocess.DEVNULL, 
         # stdout=subprocess.DEVNULL,