diff --git a/compiler/res/prog8lib/diskio.p8 b/compiler/res/prog8lib/diskio.p8
index ad70aee24..8555e3e35 100644
--- a/compiler/res/prog8lib/diskio.p8
+++ b/compiler/res/prog8lib/diskio.p8
@@ -227,13 +227,15 @@ close_end:
         return false
     }
 
-    sub f_read(uword bufferpointer, uword buffersize) -> uword {
+    sub f_read(uword bufferpointer, uword num_bytes) -> uword {
+        ; -- read from the currently open file, up to the given number of bytes.
+        ;    returns the actual number of bytes read.  (checks for End-of-file and error conditions)
         if not iteration_in_progress
             return 0
 
         uword actual = 0
         void c64.CHKIN(11)        ; use #11 as input channel again
-        repeat buffersize {
+        repeat num_bytes {
             ubyte data = c64.CHRIN()
             @(bufferpointer) = data
             bufferpointer++
@@ -247,6 +249,19 @@ close_end:
         return actual
     }
 
+    sub f_read_exact(uword bufferpointer, uword num_bytes) {
+        ; -- read from the currently open file, the given number of bytes. File must contain enough data!
+        ;    doesn't check for error conditions or end of file, to make the read as fast as possible.
+        if not iteration_in_progress
+            return
+
+        void c64.CHKIN(11)        ; use #11 as input channel again
+        repeat num_bytes {
+            @(bufferpointer) = c64.CHRIN()
+            bufferpointer++
+        }
+    }
+
     sub f_close() {
         ; -- end an iterative file loading session (close channels).
         if iteration_in_progress {
diff --git a/examples/cx16/imageviewer/iff_module.p8 b/examples/cx16/imageviewer/iff_module.p8
index 09d4089ef..ba0dc3944 100644
--- a/examples/cx16/imageviewer/iff_module.p8
+++ b/examples/cx16/imageviewer/iff_module.p8
@@ -45,7 +45,7 @@ iff_module {
 
                     while read_chunk_header() {
                         if chunk_id == "bmhd" {
-                            void diskio.f_read(buffer, chunk_size_lo)
+                            diskio.f_read_exact(buffer, chunk_size_lo)
                             width = mkword(buffer[0], buffer[1])
                             height = mkword(buffer[2], buffer[3])
                             num_planes = buffer[8]
@@ -53,7 +53,7 @@ iff_module {
                             compression = buffer[10]
                         }
                         else if chunk_id == "camg" {
-                            void diskio.f_read(buffer, chunk_size_lo)
+                            diskio.f_read_exact(buffer, chunk_size_lo)
                             camg = mkword(buffer[2], buffer[3])
                             if camg & $0800 {
                                 txt.print("ham mode not supported!\n")
@@ -62,13 +62,13 @@ iff_module {
                         }
                         else if chunk_id == "cmap" {
                             have_cmap = true
-                            void diskio.f_read(&cmap, chunk_size_lo)
+                            diskio.f_read_exact(&cmap, chunk_size_lo)
                         }
                         else if chunk_id == "crng" {
                             ; DeluxePaint color cycle range
                             if not cycle_ccrt {
                                 cycle_crng = true
-                                void diskio.f_read(buffer, chunk_size_lo)
+                                diskio.f_read_exact(buffer, chunk_size_lo)
                                 cycle_rates[num_cycles] = mkword(buffer[2], buffer[3])
                                 cycle_rate_ticks[num_cycles] = 1
                                 cycle_lows[num_cycles] = buffer[6]
@@ -82,7 +82,7 @@ iff_module {
                             ; Graphicraft color cycle range
                             if not cycle_crng {
                                 cycle_ccrt = true
-                                void diskio.f_read(buffer, chunk_size_lo)
+                                diskio.f_read_exact(buffer, chunk_size_lo)
                                 ubyte direction = buffer[1]
                                 if direction {
                                     ; delay_sec = buffer[4] * 256 * 256 * 256 + buffer[5] * 256 * 256 + buffer[6] * 256 + buffer[7]
@@ -143,9 +143,9 @@ iff_module {
 
         sub skip_chunk() {
             repeat lsb(chunk_size_hi)*8 + (chunk_size_lo >> 13)
-                void diskio.f_read(scanline_data_ptr, $2000)
+                diskio.f_read_exact(scanline_data_ptr, $2000)
 
-            void diskio.f_read(scanline_data_ptr, chunk_size_lo & $1fff)
+            diskio.f_read_exact(scanline_data_ptr, chunk_size_lo & $1fff)
         }
 
         sub make_ehb_palette() {
@@ -190,9 +190,9 @@ iff_module {
             ubyte interlaced = (camg & $0004) != 0
             uword y
             for y in 0 to height-1 {
-                void diskio.f_read(scanline_data_ptr, interleave_stride)
+                diskio.f_read_exact(scanline_data_ptr, interleave_stride)
                 if interlaced
-                    void diskio.f_read(scanline_data_ptr, interleave_stride)
+                    diskio.f_read_exact(scanline_data_ptr, interleave_stride)
                 cx16.FB_cursor_position(offsetx, offsety+y)
                 planar_to_chunky_scanline()
             }
diff --git a/examples/cx16/imageviewer/koala_module.p8 b/examples/cx16/imageviewer/koala_module.p8
index 40695c441..f297ed23d 100644
--- a/examples/cx16/imageviewer/koala_module.p8
+++ b/examples/cx16/imageviewer/koala_module.p8
@@ -11,13 +11,11 @@ koala_module {
         if diskio.f_open(8, filenameptr) {
             uword size = diskio.f_read(load_location, 2)    ; skip the first 2 bytes (load address)
             if size==2 {
-                size = diskio.f_read(load_location, 10001)
-                if size == 10001 {
-                    ; set a better C64 color palette, the Cx16's default is too saturated
-                    c64colors.set_palette_pepto()
-                    convert_koalapic()
-                    load_ok = true
-                }
+                diskio.f_read_exact(load_location, 10001)
+                ; set a better C64 color palette, the Cx16's default is too saturated
+                c64colors.set_palette_pepto()
+                convert_koalapic()
+                load_ok = true
             }
             diskio.f_close()
         }
diff --git a/examples/test.p8 b/examples/test.p8
index 74662d3a5..c73449ec5 100644
--- a/examples/test.p8
+++ b/examples/test.p8
@@ -11,14 +11,24 @@ main {
 
     ; TODO asmsub version generates LARGER CODE , why is this?
     sub vpoke(ubyte bank, uword address, ubyte value) {
-
+        %asm {{
+            rts
+        }}
     }
 
     asmsub vpokeasm(uword address @R0, ubyte bank @A, ubyte value @Y) {
-
+        %asm {{
+            rts
+        }}
     }
 
     sub start () {
         txt.chrout('!')
+        ubyte bank = 1
+        uword address = 1000
+        ubyte value = 123
+        bank++
+        vpoke(bank, address, value)
+        vpokeasm(address, bank, value)
     }
 }