diff --git a/consensus/ethash/algorithm_test.go b/consensus/ethash/algorithm_test.go
index 38477f0f71..7765ff9fe6 100644
--- a/consensus/ethash/algorithm_test.go
+++ b/consensus/ethash/algorithm_test.go
@@ -703,7 +703,7 @@ func TestConcurrentDiskCacheGeneration(t *testing.T) {
 
 		go func(idx int) {
 			defer pend.Done()
-			ethash := New(Config{cachedir, 0, 1, "", 0, 0, Normal})
+			ethash := New(Config{cachedir, 0, 1, "", 0, 0, ModeNormal})
 			if err := ethash.VerifySeal(nil, block.Header()); err != nil {
 				t.Errorf("proc %d: block verification failed: %v", idx, err)
 			}
diff --git a/consensus/ethash/consensus.go b/consensus/ethash/consensus.go
index 7a598e8e81..51bdd9e731 100644
--- a/consensus/ethash/consensus.go
+++ b/consensus/ethash/consensus.go
@@ -68,7 +68,7 @@ func (ethash *Ethash) Author(header *types.Header) (common.Address, error) {
 // stock Ethereum ethash engine.
 func (ethash *Ethash) VerifyHeader(chain consensus.ChainReader, header *types.Header, seal bool) error {
 	// If we're running a full engine faking, accept any input as valid
-	if ethash.config.PowMode == FullFake {
+	if ethash.config.PowMode == ModeFullFake {
 		return nil
 	}
 	// Short circuit if the header is known, or it's parent not
@@ -89,7 +89,7 @@ func (ethash *Ethash) VerifyHeader(chain consensus.ChainReader, header *types.He
 // a results channel to retrieve the async verifications.
 func (ethash *Ethash) VerifyHeaders(chain consensus.ChainReader, headers []*types.Header, seals []bool) (chan<- struct{}, <-chan error) {
 	// If we're running a full engine faking, accept any input as valid
-	if ethash.config.PowMode == FullFake || len(headers) == 0 {
+	if ethash.config.PowMode == ModeFullFake || len(headers) == 0 {
 		abort, results := make(chan struct{}), make(chan error, len(headers))
 		for i := 0; i < len(headers); i++ {
 			results <- nil
@@ -169,7 +169,7 @@ func (ethash *Ethash) verifyHeaderWorker(chain consensus.ChainReader, headers []
 // rules of the stock Ethereum ethash engine.
 func (ethash *Ethash) VerifyUncles(chain consensus.ChainReader, block *types.Block) error {
 	// If we're running a full engine faking, accept any input as valid
-	if ethash.config.PowMode == FullFake {
+	if ethash.config.PowMode == ModeFullFake {
 		return nil
 	}
 	// Verify that there are at most 2 uncles included in this block
@@ -455,7 +455,7 @@ func calcDifficultyFrontier(time uint64, parent *types.Header) *big.Int {
 // the PoW difficulty requirements.
 func (ethash *Ethash) VerifySeal(chain consensus.ChainReader, header *types.Header) error {
 	// If we're running a fake PoW, accept any seal as valid
-	if ethash.config.PowMode == Fake || ethash.config.PowMode == FullFake {
+	if ethash.config.PowMode == ModeFake || ethash.config.PowMode == ModeFullFake {
 		time.Sleep(ethash.fakeDelay)
 		if ethash.fakeFail == header.Number.Uint64() {
 			return errInvalidPoW
@@ -480,7 +480,7 @@ func (ethash *Ethash) VerifySeal(chain consensus.ChainReader, header *types.Head
 	cache := ethash.cache(number)
 
 	size := datasetSize(number)
-	if ethash.config.PowMode == Test {
+	if ethash.config.PowMode == ModeTest {
 		size = 32 * 1024
 	}
 	digest, result := hashimotoLight(size, cache, header.HashNoNonce().Bytes(), header.Nonce.Uint64())
diff --git a/consensus/ethash/ethash.go b/consensus/ethash/ethash.go
index 78efae1d48..a78b3a895d 100644
--- a/consensus/ethash/ethash.go
+++ b/consensus/ethash/ethash.go
@@ -45,7 +45,7 @@ var (
 	maxUint256 = new(big.Int).Exp(big.NewInt(2), big.NewInt(256), big.NewInt(0))
 
 	// sharedEthash is a full instance that can be shared between multiple users.
-	sharedEthash = New(Config{"", 3, 0, "", 1, 0, Normal})
+	sharedEthash = New(Config{"", 3, 0, "", 1, 0, ModeNormal})
 
 	// algorithmRevision is the data structure version used for file naming.
 	algorithmRevision = 23
@@ -320,14 +320,15 @@ func MakeDataset(block uint64, dir string) {
 	d.release()
 }
 
+// Mode defines the type and amount of PoW verification an ethash engine makes.
 type Mode uint
 
 const (
-	Normal Mode = iota
-	Shared
-	Test
-	Fake
-	FullFake
+	ModeNormal Mode = iota
+	ModeShared
+	ModeTest
+	ModeFake
+	ModeFullFake
 )
 
 // Config are the configuration parameters of the ethash.
@@ -392,7 +393,7 @@ func NewTester() *Ethash {
 	return &Ethash{
 		config: Config{
 			CachesInMem: 1,
-			PowMode:     Test,
+			PowMode:     ModeTest,
 		},
 		caches:   make(map[uint64]*cache),
 		datasets: make(map[uint64]*dataset),
@@ -407,7 +408,7 @@ func NewTester() *Ethash {
 func NewFaker() *Ethash {
 	return &Ethash{
 		config: Config{
-			PowMode: Fake,
+			PowMode: ModeFake,
 		},
 	}
 }
@@ -418,7 +419,7 @@ func NewFaker() *Ethash {
 func NewFakeFailer(fail uint64) *Ethash {
 	return &Ethash{
 		config: Config{
-			PowMode: Fake,
+			PowMode: ModeFake,
 		},
 		fakeFail: fail,
 	}
@@ -430,7 +431,7 @@ func NewFakeFailer(fail uint64) *Ethash {
 func NewFakeDelayer(delay time.Duration) *Ethash {
 	return &Ethash{
 		config: Config{
-			PowMode: Fake,
+			PowMode: ModeFake,
 		},
 		fakeDelay: delay,
 	}
@@ -441,7 +442,7 @@ func NewFakeDelayer(delay time.Duration) *Ethash {
 func NewFullFaker() *Ethash {
 	return &Ethash{
 		config: Config{
-			PowMode: FullFake,
+			PowMode: ModeFullFake,
 		},
 	}
 }
@@ -501,7 +502,7 @@ func (ethash *Ethash) cache(block uint64) []uint32 {
 	ethash.lock.Unlock()
 
 	// Wait for generation finish, bump the timestamp and finalize the cache
-	current.generate(ethash.config.CacheDir, ethash.config.CachesOnDisk, ethash.config.PowMode == Test)
+	current.generate(ethash.config.CacheDir, ethash.config.CachesOnDisk, ethash.config.PowMode == ModeTest)
 
 	current.lock.Lock()
 	current.used = time.Now()
@@ -509,7 +510,7 @@ func (ethash *Ethash) cache(block uint64) []uint32 {
 
 	// If we exhausted the future cache, now's a good time to regenerate it
 	if future != nil {
-		go future.generate(ethash.config.CacheDir, ethash.config.CachesOnDisk, ethash.config.PowMode == Test)
+		go future.generate(ethash.config.CacheDir, ethash.config.CachesOnDisk, ethash.config.PowMode == ModeTest)
 	}
 	return current.cache
 }
@@ -564,7 +565,7 @@ func (ethash *Ethash) dataset(block uint64) []uint32 {
 	ethash.lock.Unlock()
 
 	// Wait for generation finish, bump the timestamp and finalize the cache
-	current.generate(ethash.config.DatasetDir, ethash.config.DatasetsOnDisk, ethash.config.PowMode == Test)
+	current.generate(ethash.config.DatasetDir, ethash.config.DatasetsOnDisk, ethash.config.PowMode == ModeTest)
 
 	current.lock.Lock()
 	current.used = time.Now()
@@ -572,7 +573,7 @@ func (ethash *Ethash) dataset(block uint64) []uint32 {
 
 	// If we exhausted the future dataset, now's a good time to regenerate it
 	if future != nil {
-		go future.generate(ethash.config.DatasetDir, ethash.config.DatasetsOnDisk, ethash.config.PowMode == Test)
+		go future.generate(ethash.config.DatasetDir, ethash.config.DatasetsOnDisk, ethash.config.PowMode == ModeTest)
 	}
 	return current.dataset
 }
diff --git a/consensus/ethash/sealer.go b/consensus/ethash/sealer.go
index d7cceb11d4..c2447e4730 100644
--- a/consensus/ethash/sealer.go
+++ b/consensus/ethash/sealer.go
@@ -34,7 +34,7 @@ import (
 // the block's difficulty requirements.
 func (ethash *Ethash) Seal(chain consensus.ChainReader, block *types.Block, stop <-chan struct{}) (*types.Block, error) {
 	// If we're running a fake PoW, simply return a 0 nonce immediately
-	if ethash.config.PowMode == Fake || ethash.config.PowMode == FullFake {
+	if ethash.config.PowMode == ModeFake || ethash.config.PowMode == ModeFullFake {
 		header := block.Header()
 		header.Nonce, header.MixDigest = types.BlockNonce{}, common.Hash{}
 		return block.WithSeal(header), nil
diff --git a/console/console_test.go b/console/console_test.go
index 98d0feddac..d296807854 100644
--- a/console/console_test.go
+++ b/console/console_test.go
@@ -98,7 +98,7 @@ func newTester(t *testing.T, confOverride func(*eth.Config)) *tester {
 		Genesis:   core.DeveloperGenesisBlock(15, common.Address{}),
 		Etherbase: common.HexToAddress(testAddress),
 		Ethash: ethash.Config{
-			PowMode: ethash.Test,
+			PowMode: ethash.ModeTest,
 		},
 	}
 	if confOverride != nil {
diff --git a/eth/backend.go b/eth/backend.go
index 8d08feca60..e7f0f57dd4 100644
--- a/eth/backend.go
+++ b/eth/backend.go
@@ -216,13 +216,13 @@ func CreateConsensusEngine(ctx *node.ServiceContext, config *ethash.Config, chai
 	}
 	// Otherwise assume proof-of-work
 	switch {
-	case config.PowMode == ethash.Fake:
+	case config.PowMode == ethash.ModeFake:
 		log.Warn("Ethash used in fake mode")
 		return ethash.NewFaker()
-	case config.PowMode == ethash.Test:
+	case config.PowMode == ethash.ModeTest:
 		log.Warn("Ethash used in test mode")
 		return ethash.NewTester()
-	case config.PowMode == ethash.Shared:
+	case config.PowMode == ethash.ModeShared:
 		log.Warn("Ethash used in shared mode")
 		return ethash.NewShared()
 	default: