diff --git a/pmtiles/makesync.go b/pmtiles/makesync.go
index b0753df..cf90d1f 100644
--- a/pmtiles/makesync.go
+++ b/pmtiles/makesync.go
@@ -4,7 +4,6 @@ import (
 	"bufio"
 	"bytes"
 	"context"
-	"crypto/md5"
 	"fmt"
 	"github.com/dustin/go-humanize"
 	"github.com/schollz/progressbar/v3"
@@ -14,8 +13,10 @@ import (
 	"log"
 	"os"
 	"runtime"
+	"sort"
 	"strconv"
 	"strings"
+	"sync"
 	"time"
 )
 
@@ -24,6 +25,7 @@ type Block struct {
 	Start  uint64 // the start tileID
 	Offset uint64 // the offset in the file, in bytes
 	Length uint64 // the length, in bytes
+	Data   []byte
 }
 
 type Result struct {
@@ -31,6 +33,12 @@ type Result struct {
 	Hash  uint64
 }
 
+type Syncline struct {
+	Offset uint64
+	Length uint64
+	Hash   uint64
+}
+
 func Makesync(logger *log.Logger, cli_version string, file string, block_size_kb int, checksum string) error {
 	ctx := context.Background()
 	start := time.Now()
@@ -96,21 +104,23 @@ func Makesync(logger *log.Logger, cli_version string, file string, block_size_kb
 	defer output.Close()
 	output.Write([]byte(fmt.Sprintf("version=%s\n", cli_version)))
 
-	if checksum == "md5" {
-		localfile, err := os.Open(file)
-		if err != nil {
-			panic(err)
-		}
-		defer localfile.Close()
-		reader := bufio.NewReaderSize(localfile, 64*1024*1024)
-		md5hasher := md5.New()
-		if _, err := io.Copy(md5hasher, reader); err != nil {
-			panic(err)
-		}
-		md5checksum := md5hasher.Sum(nil)
-		fmt.Printf("Completed md5 in %v.\n", time.Since(start))
-		output.Write([]byte(fmt.Sprintf("md5=%x\n", md5checksum)))
+	// open a 2nd copy as a plain file
+	localfile, err := os.Open(file)
+	if err != nil {
+		panic(err)
 	}
+	defer localfile.Close()
+	reader := bufio.NewReaderSize(localfile, 64*1024*1024)
+
+	// if checksum == "md5" {
+	// 	md5hasher := md5.New()
+	// 	if _, err := io.Copy(md5hasher, reader); err != nil {
+	// 		panic(err)
+	// 	}
+	// 	md5checksum := md5hasher.Sum(nil)
+	// 	fmt.Printf("Completed md5 in %v.\n", time.Since(start))
+	// 	output.Write([]byte(fmt.Sprintf("md5=%x\n", md5checksum)))
+	// }
 
 	output.Write([]byte("hash=fnv1a\n"))
 	output.Write([]byte(fmt.Sprintf("blocksize=%d\n", block_size_bytes)))
@@ -122,64 +132,34 @@ func Makesync(logger *log.Logger, cli_version string, file string, block_size_kb
 
 	var current Block
 
-	GetHash := func(offset uint64, length uint64) uint64 {
-		hasher := fnv.New64a()
-		r, err := bucket.NewRangeReader(ctx, key, int64(header.TileDataOffset+offset), int64(length))
-		if err != nil {
-			log.Fatal(err)
-		}
-
-		if _, err := io.Copy(hasher, r); err != nil {
-			log.Fatal(err)
-		}
-		r.Close()
-		return hasher.Sum64()
-	}
-
 	tasks := make(chan Block, 10000)
-	intermediate := make(chan Result, 10000)
+
+	var wg sync.WaitGroup
+	var mu sync.Mutex
+	items := make(map[uint64]Syncline)
 
 	errs, _ := errgroup.WithContext(ctx)
+	
 	// workers
 	for i := 0; i < runtime.GOMAXPROCS(0); i++ {
+		wg.Add(1)
+		hasher := fnv.New64a()
 		errs.Go(func() error {
 			for block := range tasks {
-				intermediate <- Result{block, GetHash(block.Offset, block.Length)}
+				if _, err := io.Copy(hasher, bytes.NewReader(block.Data)); err != nil {
+					return err
+				}
+				mu.Lock()
+				items[block.Start] = Syncline{block.Offset, block.Length, hasher.Sum64()}
+				mu.Unlock()
+
+				hasher.Reset()
 			}
+			wg.Done()
 			return nil
 		})
 	}
 
-	done := make(chan struct{})
-
-	go func() {
-		buffer := make(map[uint64]Result)
-		nextIndex := uint64(0)
-
-		for i := range intermediate {
-			buffer[i.Block.Index] = i
-
-			for {
-				if next, ok := buffer[nextIndex]; ok {
-
-					output.Write([]byte(fmt.Sprintf("%d\t%d\t%d\t%x\n", next.Block.Start, next.Block.Offset, next.Block.Length, next.Hash)))
-
-					delete(buffer, nextIndex)
-					nextIndex++
-
-					if next.Block.Offset+next.Block.Length == header.TileDataLength {
-						close(intermediate)
-					}
-
-				} else {
-					break
-				}
-			}
-		}
-
-		done <- struct{}{}
-	}()
-
 	current_index := uint64(0)
 
 	blocks := 0
@@ -196,7 +176,13 @@ func Makesync(logger *log.Logger, cli_version string, file string, block_size_kb
 			panic("Invalid clustering of archive detected - check with verify")
 		} else {
 			if current.Length+uint64(e.Length) > block_size_bytes {
-				tasks <- Block{current.Index, current.Start, current.Offset, current.Length}
+				data := make([]byte, current.Length)
+				_, err := io.ReadFull(reader, data)
+				if err != nil {
+					panic(err)
+				}
+
+				tasks <- Block{current.Index, current.Start, current.Offset, current.Length, data}
 				blocks += 1
 
 				current_index += 1
@@ -210,22 +196,35 @@ func Makesync(logger *log.Logger, cli_version string, file string, block_size_kb
 		}
 	})
 
-	tasks <- Block{current.Index, current.Start, current.Offset, current.Length}
+	data := make([]byte, current.Length)
+	_, err = io.ReadFull(reader, data)
+	if err != nil {
+		return err
+	}
+	tasks <- Block{current.Index, current.Start, current.Offset, current.Length, data}
 	blocks += 1
 	close(tasks)
 
-	<-done
+	wg.Wait()
+
+	// serialize the hash
+
+	var keys []uint64
+	for k := range items {
+		keys = append(keys, k)
+	}
+	sort.Slice(keys, func(i, j int) bool { return keys[i] < keys[j] })
+
+	for _, k := range keys {
+		syncline := items[k]
+		output.Write([]byte(fmt.Sprintf("%d\t%d\t%d\t%x\n", k, syncline.Offset, syncline.Length, syncline.Hash)))
+	}
+
 	fmt.Printf("Created syncfile with %d blocks.\n", blocks)
 	fmt.Printf("Completed makesync in %v.\n", time.Since(start))
 	return nil
 }
 
-type Syncline struct {
-	Offset uint64
-	Length uint64
-	Hash   uint64
-}
-
 func Sync(logger *log.Logger, file string, syncfile string) error {
 	start := time.Now()
 	total_remote_bytes := uint64(0)