diff --git a/lib/sata/__init__.py b/lib/sata/__init__.py
index 34c7a3534..0a167bdc7 100644
--- a/lib/sata/__init__.py
+++ b/lib/sata/__init__.py
@@ -3,11 +3,19 @@ from lib.sata.link import SATALink
 from lib.sata.transport import SATATransport
 from lib.sata.command import SATACommand
 
+from lib.sata.frontend.crossbar import SATACrossbar
+
 class SATACON(Module):
 	def __init__(self, phy):
 		###
+		# core
 		self.link = SATALink(phy)
 		self.transport = SATATransport(self.link)
 		self.command = SATACommand(self.transport)
-		self.sink, self.source = self.command.sink, self.command.source
 
+		# frontend
+		self.crossbar = SATACrossbar(32)
+		self.comb += [
+			Record.connect(self.crossbar.master.source, self.command.sink),
+			Record.connect(self.command.source, self.crossbar.master.sink)
+		]
diff --git a/lib/sata/bist.py b/lib/sata/bist.py
index 4948022fd..5de8e7c1a 100644
--- a/lib/sata/bist.py
+++ b/lib/sata/bist.py
@@ -1,22 +1,90 @@
 from lib.sata.common import *
 from lib.sata.link.scrambler import Scrambler
+
+from migen.fhdl.decorators import ModuleDecorator
 from migen.bank.description import *
 
-class SATABIST(Module):
-	def __init__(self, sata_con):
-		self.write = Signal()
-		self.read = Signal()
+class SATABISTGenerator(Module):
+	def __init__(self, sata_master_port):
+		self.start = Signal()
 		self.sector = Signal(48)
 		self.count = Signal(16)
 		self.loops = Signal(8)
+		self.random = Signal()
+
+		self.done = Signal()
+		self.errors = Signal(32) # Note: Not used for writes
+
+		###
+
+		source, sink = sata_master_port.source, sata_master_port.sink
+
+		self.counter = counter = Counter(bits_sign=32)
+		self.loops_counter = loops_counter = Counter(bits_sign=8)
+
+		self.scrambler = scrambler = InsertReset(Scrambler())
+		self.comb += [
+			scrambler.reset.eq(counter.reset),
+			scrambler.ce.eq(counter.ce)
+		]
+
+		self.fsm = fsm = FSM(reset_state="IDLE")
+		fsm.act("IDLE",
+			self.done.eq(1),
+			counter.reset.eq(1),
+			loops_counter.reset.eq(1),
+			If(self.start,
+				NextState("SEND_CMD_AND_DATA")
+			)
+		)
+		self.comb += [
+			source.sop.eq(counter.value == 0),
+			source.eop.eq(counter.value == (logical_sector_size//4*self.count)-1),
+			source.write.eq(1),
+			source.sector.eq(self.sector),
+			source.count.eq(self.count),
+			If(self.random,
+				source.data.eq(scrambler.value)
+			).Else(
+				source.data.eq(counter.value)
+			)
+		]
+		fsm.act("SEND_CMD_AND_DATA",
+			source.stb.eq(1),
+			If(source.stb & source.ack,
+				counter.ce.eq(1),
+				If(source.eop,
+					NextState("WAIT_ACK")
+				)
+			)
+		)
+		fsm.act("WAIT_ACK",
+			sink.ack.eq(1),
+			If(sink.stb,
+				loops_counter.ce.eq(1),
+				If(loops_counter.value == (self.loops-1),
+					NextState("IDLE")
+				).Else(
+					counter.reset.eq(1),
+					NextState("SEND_CMD_AND_DATA")
+				)
+			)
+		)
+
+class SATABISTChecker(Module):
+	def __init__(self, sata_master_port):
+		self.start = Signal()
+		self.sector = Signal(48)
+		self.count = Signal(16)
+		self.loops = Signal(8)
+		self.random = Signal()
 
 		self.done = Signal()
 		self.errors = Signal(32)
 
-	###
+		###
 
-		sink = sata_con.source
-		source = sata_con.sink
+		source, sink = sata_master_port.source, sata_master_port.sink
 
 		self.counter = counter = Counter(bits_sign=32)
 		self.loops_counter = loops_counter = Counter(bits_sign=8)
@@ -33,63 +101,42 @@ class SATABIST(Module):
 			self.done.eq(1),
 			counter.reset.eq(1),
 			loops_counter.reset.eq(1),
-			If(self.write,
+			If(self.start,
 				self.error_counter.reset.eq(1),
-				NextState("SEND_WRITE_CMD_AND_DATA")
-			).Elif(self.read,
-				self.error_counter.reset.eq(1),
-				NextState("SEND_READ_CMD")
+				NextState("SEND_CMD")
 			)
 		)
-		fsm.act("SEND_WRITE_CMD_AND_DATA",
-			source.stb.eq(1),
-			source.sop.eq(counter.value == 0),
-			source.eop.eq(counter.value == (logical_sector_size//4*self.count)-1),
-			source.write.eq(1),
-			source.sector.eq(self.sector),
-			source.count.eq(self.count),
-			source.data.eq(scrambler.value),
-			If(source.stb & source.ack,
-				counter.ce.eq(1),
-				If(source.eop,
-					NextState("WAIT_WRITE_ACK")
-				)
-			)
-		)
-		fsm.act("WAIT_WRITE_ACK",
-			sink.ack.eq(1),
-			If(sink.stb,
-				loops_counter.ce.eq(1),
-				If(loops_counter.value == (self.loops-1),
-					NextState("IDLE")
-				).Else(
-					counter.reset.eq(1),
-					NextState("SEND_WRITE_CMD_AND_DATA")
-				)
-			)
-		)
-		fsm.act("SEND_READ_CMD",
-			source.stb.eq(1),
+		self.comb += [
 			source.sop.eq(1),
 			source.eop.eq(1),
 			source.read.eq(1),
 			source.sector.eq(self.sector),
 			source.count.eq(self.count),
+		]
+		fsm.act("SEND_CMD",
+			source.stb.eq(1),
 			If(source.ack,
 				counter.reset.eq(1),
-				NextState("WAIT_READ_ACK")
+				NextState("WAIT_ACK")
 			)
 		)
-		fsm.act("WAIT_READ_ACK",
+		fsm.act("WAIT_ACK",
 			If(sink.stb & sink.read,
-				NextState("RECEIVE_READ_DATA")
+				NextState("RECEIVE_DATA")
 			)
 		)
-		fsm.act("RECEIVE_READ_DATA",
+		expected_data = Signal(32)
+		self.comb += \
+			If(self.random,
+				expected_data.eq(scrambler.value)
+			).Else(
+				expected_data.eq(counter.value)
+			)
+		fsm.act("RECEIVE_DATA",
 			sink.ack.eq(1),
 			If(sink.stb,
 				counter.ce.eq(1),
-				If(sink.data != scrambler.value,
+				If(sink.data != expected_data,
 					self.error_counter.ce.eq(1)
 				),
 				If(sink.eop,
@@ -98,33 +145,45 @@ class SATABIST(Module):
 						If(loops_counter.value == (self.loops-1),
 							NextState("IDLE")
 						).Else(
-							NextState("SEND_READ_CMD")
+							NextState("SEND_CMD")
 						)
 					).Else(
-						NextState("WAIT_READ_ACK")
+						NextState("WAIT_ACK")
 					)
 				)
 			)
 		)
 
 class SATABISTControl(Module, AutoCSR):
-	def __init__(self, sata_bist):
-		self._write = CSR()
-		self._read = CSR()
+	def __init__(self, bist_unit):
+		self._start = CSR()
 		self._sector = CSRStorage(48)
 		self._count = CSRStorage(16)
+		self._random = CSRStorage()
 		self._loops = CSRStorage(8)
-
 		self._done = CSRStatus()
 		self._errors = CSRStatus(32)
 
+		###
+		self.bist_unit = bist_unit
 		self.comb += [
-			sata_bist.write.eq(self._write.r & self._write.re),
-			sata_bist.read.eq(self._read.r & self._read.re),
-			sata_bist.sector.eq(self._sector.storage),
-			sata_bist.count.eq(self._count.storage),
-			sata_bist.loops.eq(self._loops.storage),
+			bist_unit.start.eq(self._start.r & self._start.re),
+			bist_unit.sector.eq(self._sector.storage),
+			bist_unit.count.eq(self._count.storage),
+			bist_unit.loops.eq(self._loops.storage),
+			bist_unit.random.eq(self._random.storage),
 
-			self._done.status.eq(sata_bist.done),
-			self._errors.status.eq(sata_bist.errors)
+			self._done.status.eq(bist_unit.done),
+			self._errors.status.eq(bist_unit.errors)
 		]
+
+class SATABIST(Module, AutoCSR):
+	def __init__(self, sata_master_ports, with_control=False):
+		generator = SATABISTGenerator(sata_master_ports[0])
+		checker = SATABISTChecker(sata_master_ports[1])
+		if with_control:
+			self.generator = SATABISTControl(generator)
+			self.checker = SATABISTControl(checker)
+		else:
+			self.generator = generator
+			self.checker = checker
diff --git a/lib/sata/command/__init__.py b/lib/sata/command/__init__.py
index dafc535b2..8b2ce5b8c 100644
--- a/lib/sata/command/__init__.py
+++ b/lib/sata/command/__init__.py
@@ -26,6 +26,7 @@ class SATACommandTX(Module):
 			transport.sink.count.eq(sink.count),
 			transport.sink.icc.eq(0),
 			transport.sink.control.eq(0),
+			transport.sink.data.eq(sink.data)
 		]
 
 		self.dwords_counter = dwords_counter = Counter(max=fis_max_dwords)
@@ -70,7 +71,6 @@ class SATACommandTX(Module):
 			transport.sink.eop.eq((dwords_counter.value == (fis_max_dwords-1)) | sink.eop),
 
 			transport.sink.type.eq(fis_types["DATA"]),
-			transport.sink.data.eq(sink.data),
 			sink.ack.eq(transport.sink.ack),
 			If(sink.stb & sink.ack,
 				If(sink.eop,
@@ -171,11 +171,13 @@ class SATACommandRX(Module):
 				)
 			)
 		)
-		fsm.act("PRESENT_READ_DATA",
-			data_buffer.sink.stb.eq(transport.source.stb),
+		self.comb += [
 			data_buffer.sink.sop.eq(transport.source.sop),
 			data_buffer.sink.eop.eq(transport.source.eop),
-			data_buffer.sink.data.eq(transport.source.data),
+			data_buffer.sink.data.eq(transport.source.data)
+		]
+		fsm.act("PRESENT_READ_DATA",
+			data_buffer.sink.stb.eq(transport.source.stb),
 			transport.source.ack.eq(data_buffer.sink.ack),
 			If(data_buffer.sink.stb & data_buffer.sink.ack,
 				self.dwords_counter.ce.eq(~read_done),
@@ -230,6 +232,7 @@ class SATACommandRX(Module):
 			source.last.eq(cmd_buffer.source.last),
 			source.success.eq(cmd_buffer.source.success),
 			source.failed.eq(cmd_buffer.source.success),
+			source.data.eq(data_buffer.source.data)
 		]
 
 		out_fsm.act("PRESENT_RESPONSE_WITH_DATA",
@@ -237,7 +240,6 @@ class SATACommandRX(Module):
 			source.sop.eq(data_buffer.source.sop),
 			source.eop.eq(data_buffer.source.eop),
 
-			source.data.eq(data_buffer.source.data),
 			data_buffer.source.ack.eq(source.ack),
 
 			If(source.stb & source.eop & source.ack,
diff --git a/lib/sata/common.py b/lib/sata/common.py
index ecb6723a3..32cabdc7b 100644
--- a/lib/sata/common.py
+++ b/lib/sata/common.py
@@ -210,6 +210,7 @@ class Counter(Module):
 		self.width = flen(self.value)
 		self.sync += self.value.eq(self.value+1)
 
+# XXX use ModuleDecorator
 class BufferizeEndpoints(Module):
 	def __init__(self, decorated, *args):
 		self.decorated = decorated
diff --git a/lib/sata/frontend/arbiter.py b/lib/sata/frontend/arbiter.py
new file mode 100644
index 000000000..678f2d7a2
--- /dev/null
+++ b/lib/sata/frontend/arbiter.py
@@ -0,0 +1,31 @@
+from lib.sata.common import *
+from lib.sata.frontend.common import *
+
+from migen.genlib.roundrobin import *
+
+class SATAArbiter(Module):
+	def __init__(self, slaves, master):
+		if len(slaves) == 1:
+			self.comb += slaves[0].connect(master)
+		else:
+			self.rr = RoundRobin(len(slaves))
+			self.grant = self.rr.grant
+			cases = {}
+			for i, slave in enumerate(slaves):
+				sink, source = slave.sink, slave.source
+				start = Signal()
+				done = Signal()
+				ongoing = Signal()
+				self.comb += [
+					start.eq(sink.stb & sink.sop),
+					done.eq(source.stb & source.last & source.eop & source.ack)
+				]
+				self.sync += \
+					If(start,
+						ongoing.eq(1)
+					).Elif(done,
+						ongoing.eq(0)
+					)
+				self.comb += self.rr.request[i].eq((start | ongoing) & ~done)
+				cases[i] = [slaves[i].connect(master)]
+			self.comb += Case(self.grant, cases)
diff --git a/lib/sata/frontend/common.py b/lib/sata/frontend/common.py
new file mode 100644
index 000000000..114a0a834
--- /dev/null
+++ b/lib/sata/frontend/common.py
@@ -0,0 +1,23 @@
+from lib.sata.common import *
+
+class SATAMasterPort:
+	def __init__(self, dw):
+		self.source = Source(command_tx_description(dw))
+		self.sink = Sink(command_rx_description(dw))
+
+	def connect(self, slave):
+		return [
+			Record.connect(self.source, slave.sink),
+			Record.connect(slave.source, self.sink)
+		]
+
+class SATASlavePort:
+	def __init__(self, dw):
+		self.sink = Sink(command_tx_description(dw))
+		self.source = Source(command_rx_description(dw))
+
+	def connect(self, master):
+		return [
+			Record.connect(self.sink, master.source),
+			Record.connect(master.sink, self.source)
+		]
diff --git a/lib/sata/frontend/crossbar.py b/lib/sata/frontend/crossbar.py
new file mode 100644
index 000000000..41ac806e8
--- /dev/null
+++ b/lib/sata/frontend/crossbar.py
@@ -0,0 +1,25 @@
+from lib.sata.common import *
+from lib.sata.frontend.common import *
+from lib.sata.frontend.arbiter import SATAArbiter
+
+class SATACrossbar(Module):
+	def __init__(self, dw):
+		self.dw = dw
+		self.slaves = []
+		self.master = SATAMasterPort(dw)
+
+	def get_port(self):
+		master = SATAMasterPort(self.dw)
+		slave = SATASlavePort(self.dw)
+		self.comb += master.connect(slave)
+		self.slaves.append(slave)
+		return master
+
+	def get_ports(self, n):
+		masters = []
+		for i in range(n):
+			masters.append(self.get_port())
+		return masters
+
+	def do_finalize(self):
+		self.arbiter = SATAArbiter(self.slaves, self.master)
diff --git a/lib/sata/link/__init__.py b/lib/sata/link/__init__.py
index 381bba88b..b142e68cb 100644
--- a/lib/sata/link/__init__.py
+++ b/lib/sata/link/__init__.py
@@ -187,10 +187,12 @@ class SATALinkRX(Module):
 				NextState("COPY")
 			)
 		)
+		self.comb += [
+			scrambler.sink.sop.eq(sop),
+			scrambler.sink.eop.eq(eop)
+		]
 		fsm.act("COPY",
 			scrambler.sink.stb.eq(cont.source.stb & ((det == 0) | eop)),
-			scrambler.sink.sop.eq(sop),
-			scrambler.sink.eop.eq(eop),
 			insert.eq(primitives["R_IP"]),
 			If(det == primitives["HOLD"],
 				insert.eq(primitives["HOLDA"])
diff --git a/lib/sata/test/bist_tb.py b/lib/sata/test/bist_tb.py
index 064767377..72c99979f 100644
--- a/lib/sata/test/bist_tb.py
+++ b/lib/sata/test/bist_tb.py
@@ -1,6 +1,6 @@
 from lib.sata.common import *
 from lib.sata import SATACON
-from lib.sata.bist import SATABIST
+from lib.sata.bist import SATABISTGenerator, SATABISTChecker
 
 from lib.sata.test.hdd import *
 from lib.sata.test.common import *
@@ -11,31 +11,35 @@ class TB(Module):
 				link_debug=False, link_random_level=0,
 				transport_debug=False, transport_loopback=False,
 				hdd_debug=True)
-		self.con = SATACON(self.hdd.phy)
-		self.bist = SATABIST(self.con)
+		self.controller = SATACON(self.hdd.phy)
+		self.generator = SATABISTGenerator(self.controller.crossbar.get_port())
+		self.checker = SATABISTChecker(self.controller.crossbar.get_port())
 
 	def gen_simulation(self, selfp):
 		hdd = self.hdd
 		hdd.malloc(0, 64)
-		selfp.bist.sector = 0
-		selfp.bist.count = 17
-		selfp.bist.loops = 1
+		selfp.generator.sector = 0
+		selfp.generator.count = 17
+		selfp.checker.sector = 0
+		selfp.checker.count = 17
 		while True:
-			selfp.bist.write = 1
+			selfp.generator.start = 1
 			yield
-			selfp.bist.write = 0
+			selfp.generator.start = 0
 			yield
-			while selfp.bist.done == 0:
+			while selfp.generator.done == 0:
 				yield
-			selfp.bist.read = 1
+			selfp.checker.start = 1
 			yield
-			selfp.bist.read = 0
+			selfp.checker.start = 0
 			yield
-			while selfp.bist.done == 0:
+			while selfp.checker.done == 0:
 				yield
-			print("errors {}".format(selfp.bist.errors))
-			selfp.bist.sector += 1
-			selfp.bist.count = max((selfp.bist.count + 1)%8, 1)
+			print("errors {}".format(selfp.checker.errors))
+			selfp.generator.sector += 1
+			selfp.generator.count = max((selfp.generator.count + 1)%8, 1)
+			selfp.checker.sector += 1
+			selfp.checker.count = max((selfp.checker.count + 1)%8, 1)
 
 if __name__ == "__main__":
 	run_simulation(TB(), ncycles=8192*2, vcd_name="my.vcd", keep_files=True)
diff --git a/targets/test.py b/targets/test.py
index 850086ee3..e186ba8c6 100644
--- a/targets/test.py
+++ b/targets/test.py
@@ -159,8 +159,8 @@ class DebugLeds(Module):
 class TestDesign(UART2WB, AutoCSR):
 	default_platform = "kc705"
 	csr_map = {
-		"sata_bist_ctrl":	10,
-		"mila":				11
+		"sata_bist":	10,
+		"mila":			11
 	}
 	csr_map.update(UART2WB.csr_map)
 
@@ -171,9 +171,8 @@ class TestDesign(UART2WB, AutoCSR):
 
 		self.sata_phy = SATAPHY(platform.request("sata_host"), clk_freq, speed="SATA2")
 		self.sata_con = SATACON(self.sata_phy)
-		self.sata_bist = SATABIST(self.sata_con)
-		self.sata_bist_ctrl = SATABISTControl(self.sata_bist)
 
+		self.sata_bist = SATABIST(self.sata_con.crossbar.get_ports(2), with_control=True)
 
 		self.leds = DebugLeds(platform, self.sata_phy)
 
@@ -189,22 +188,22 @@ class TestDesign(UART2WB, AutoCSR):
 				self.sata_phy.sink.data,
 				self.sata_phy.sink.charisk,
 
-				self.sata_con.sink.stb,
-				self.sata_con.sink.sop,
-				self.sata_con.sink.eop,
-				self.sata_con.sink.ack,
-				self.sata_con.sink.write,
-				self.sata_con.sink.read,
+				self.sata_con.command.sink.stb,
+				self.sata_con.command.sink.sop,
+				self.sata_con.command.sink.eop,
+				self.sata_con.command.sink.ack,
+				self.sata_con.command.sink.write,
+				self.sata_con.command.sink.read,
 
-				self.sata_con.source.stb,
-				self.sata_con.source.sop,
-				self.sata_con.source.eop,
-				self.sata_con.source.ack,
-				self.sata_con.source.write,
-				self.sata_con.source.read,
-				self.sata_con.source.success,
-				self.sata_con.source.failed,
-				self.sata_con.source.data
+				self.sata_con.command.source.stb,
+				self.sata_con.command.source.sop,
+				self.sata_con.command.source.eop,
+				self.sata_con.command.source.ack,
+				self.sata_con.command.source.write,
+				self.sata_con.command.source.read,
+				self.sata_con.command.source.success,
+				self.sata_con.command.source.failed,
+				self.sata_con.command.source.data
 			)
 
 			self.mila = MiLa(depth=2048, dat=Cat(*debug))
diff --git a/test/bist.py b/test/bist.py
index 86d116a2e..82d11a726 100644
--- a/test/bist.py
+++ b/test/bist.py
@@ -5,35 +5,57 @@ from config import *
 logical_sector_size = 512
 
 class SATABISTDriver:
-	def __init__(self, regs):
+	def __init__(self, regs, name):
 		self.regs = regs
+		self.name = name
+		for s in ["start", "sector", "count", "loops", "random", "done", "errors"]:
+			setattr(self, s, getattr(regs, name + "_"+ s))
 
-	def run(self, sector, count, loops, mode):
-		self.regs.sata_bist_ctrl_sector.write(sector)
-		self.regs.sata_bist_ctrl_count.write(count)
-		self.regs.sata_bist_ctrl_loops.write(loops)
-		if mode == "write":
-			self.regs.sata_bist_ctrl_write.write(1)
-		elif mode == "read":
-			self.regs.sata_bist_ctrl_read.write(1)
-		while (self.regs.sata_bist_ctrl_done.read() == 0):
+	def run(self, sector, count, loops, random):
+		self.sector.write(sector)
+		self.count.write(count)
+		self.loops.write(loops)
+		self.random.write(random)
+		self.start.write(1)
+		while (self.done.read() == 0):
 			pass
-		return self.regs.sata_bist_ctrl_errors.read()
+		return self.errors.read()
 
-	def write(self, sector, count, loops):
-		self.run(sector, count, loops, "write")
+class SATABISTGeneratorDriver(SATABISTDriver):
+	def __init__(self, regs, name):
+		SATABISTDriver.__init__(self, regs, name + "_generator")
 
-	def read(self, sector, count, loops):
-		return self.run(sector, count, loops, "read")
+class SATABISTCheckerDriver(SATABISTDriver):
+	def __init__(self, regs, name):
+		SATABISTDriver.__init__(self, regs, name + "_checker")
+
+class Timer:
+	def __init__(self):
+		self.value = None
+
+	def start(self):
+		self._start = time.time()
+
+	def stop(self):
+		self._stop = time.time()
+		self.value = self._stop - self._start
+
+KB = 1024
+MB = 1024*KB
+GB = 1024*MB
+
+def compute_speed(loops, count, elapsed_time, unit):
+	return loops*count*logical_sector_size/unit/elapsed_time
 
 def _get_args():
 	parser = argparse.ArgumentParser(formatter_class=argparse.RawDescriptionHelpFormatter,
 		description="""\
 SATA BIST utility.
 """)
-	parser.add_argument("-s", "--sector", default=0, help="BIST start sector")
-	parser.add_argument("-c", "--count", default=16384, help="BIST count (number of sectors per transaction)")
-	parser.add_argument("-l", "--loops", default=4, help="BIST loops (number of loop for each transaction")
+	parser.add_argument("-s", "--sector", default=0, help="start sector")
+	parser.add_argument("-c", "--count", default=16384, help="number of sectors per transaction")
+	parser.add_argument("-l", "--loops", default=4, help="number of loop for each transaction")
+	parser.add_argument("-r", "--random", default=True, help="use random data")
 
 	return parser.parse_args()
 
@@ -41,31 +63,30 @@ if __name__ == "__main__":
 	args = _get_args()
 	wb.open()
 	###
-	bist = SATABISTDriver(wb.regs)
+	generator = SATABISTGeneratorDriver(wb.regs, "sata_bist")
+	checker = SATABISTCheckerDriver(wb.regs, "sata_bist")
+	timer = Timer()
+
 	sector = int(args.sector)
 	count = int(args.count)
 	loops = int(args.loops)
+	random = int(args.random)
 	try:
-		write_time = 0
-		read_time = 0
 		while True:
-			# Write
-			start = time.time()
-			bist.write(sector, count, loops)
-			end = time.time()
-			write_time = end-start
-			write_speed = loops*count*logical_sector_size/(1024*1024)/write_time
-
-			# Read
-			start = time.time()
-			read_errors = bist.read(sector, count, loops)
-			end = time.time()
-			read_time = end-start
-			read_speed = loops*count*logical_sector_size/(1024*1024)/read_time
+			# generator (write data to HDD)
+			timer.start()
+			generator.run(sector, count, loops, random)
+			timer.stop()
+			write_speed = compute_speed(loops, count, timer.value, MB)
 
+			# checker (read and check data from HDD)
+			timer.start()
+			errors = checker.run(sector, count, loops, random)
+			timer.stop()
+			read_speed = compute_speed(loops, count, timer.value, MB)
 			sector += count
 
-			print("sector=%d write_speed=%4.2fMB/sec read_speed=%4.2fMB/sec errors=%d" %(sector, write_speed, read_speed, read_errors))
+			print("sector=%d write_speed=%4.2fMB/sec read_speed=%4.2fMB/sec errors=%d" %(sector, write_speed, read_speed, errors))
 
 	except KeyboardInterrupt:
 		pass