diff -ur usbasp.2007-10-23/firmware/isp.c usbasp.2007-10-23-new/firmware/isp.c
--- usbasp.2007-10-23/firmware/isp.c	2007-07-23 19:31:26.000000000 +0300
+++ usbasp.2007-10-23-new/firmware/isp.c	2008-03-29 21:08:47.000000000 +0200
@@ -15,33 +15,82 @@
 
 #define spiHWdisable() SPCR = 0
 
-void spiHWenable() {
+uchar clock_div; /* hardware divider index */
+uchar sw_delay=12;
 
-  /* enable SPI, master, 375kHz SCK */
-  SPCR = (1 << SPE) | (1 << MSTR) | (1 << SPR1);
-  SPSR = (1 << SPI2X);
+void spiHWenable() {
+  switch (clock_div) {
+  case ISP_SCK_1500:
+    /* enable SPI, master, 1.5MHz, XTAL/8 */
+    SPCR = (1 << SPE) | (1 << MSTR) | (1 << SPR0);
+    SPSR = (1 << SPI2X);      
+  case ISP_SCK_750:
+    /* enable SPI, master, 750kHz, XTAL/16 */
+    SPCR = (1 << SPE) | (1 << MSTR) | (1 << SPR0);
+    SPSR = 0;
+    break;
+  case ISP_SCK_375:
+  default:
+    /* enable SPI, master, 375kHz, XTAL/32 (default) */
+    SPCR = (1 << SPE) | (1 << MSTR) | (1 << SPR1);
+    SPSR = (1 << SPI2X);
+    break;
+  case ISP_SCK_187_5:
+    /* enable SPI, master, 187.5kHz XTAL/64 */
+    SPCR = (1 << SPE) | (1 << MSTR) | (1 << SPR1);
+    SPSR = 0;
+    break;
+  case ISP_SCK_93_75:
+    /* enable SPI, master, 93.75kHz XTAL/128 */
+    SPCR = (1 << SPE) | (1 << MSTR) | (1 << SPR1)| (1 << SPR0);
+    SPSR = 0;
+    break;
+  }
 }
 
 void ispSetSCKOption(uchar option) {
 
-  if (option == 0) {
-
-    /* use software spi */
-    ispTransmit = ispTransmit_sw;
-    //    spiHWdisable();
-
-  } else {
+  if (option >= ISP_SCK_93_75) {
 
     /* use hardware spi */
     ispTransmit = ispTransmit_hw;
+    clock_div = option;
+
+  } else {
+    /* use software spi */
+    ispTransmit = ispTransmit_sw;
 
+    switch (option) {
+    case ISP_SCK_32:
+      sw_delay = 3;
+      break;
+    case ISP_SCK_16:
+      sw_delay = 6;
+      break;
+    case ISP_SCK_8:
+    default:
+      sw_delay = 12;
+      break;
+    case ISP_SCK_4:
+      sw_delay = 24;
+      break;
+    case ISP_SCK_2:
+      sw_delay = 48;
+      break;	
+    case ISP_SCK_1:
+      sw_delay = 96;
+      break;	
+    case ISP_SCK_0_5:
+      sw_delay = 192;
+      break;	
+    }
   }
 }
   
 void ispDelay() {
 
   uint8_t starttime = TIMERVALUE;
-  while ((uint8_t) (TIMERVALUE - starttime) < 12) { }
+  while ((uint8_t) (TIMERVALUE - starttime) < sw_delay) { }
 }
 
 void ispConnect() {
diff -ur usbasp.2007-10-23/firmware/isp.h usbasp.2007-10-23-new/firmware/isp.h
--- usbasp.2007-10-23/firmware/isp.h	2007-07-23 19:31:20.000000000 +0300
+++ usbasp.2007-10-23-new/firmware/isp.h	2008-03-29 21:09:19.000000000 +0200
@@ -24,9 +24,32 @@
 #define ISP_MISO  PB4
 #define ISP_SCK   PB5
 
+/* ISP SCK speed indexes */
+/* software ISP modes */
+#define ISP_SCK_0_5    23  /*   500 Hz */
+#define ISP_SCK_1      24  /*   1 kHz */
+#define ISP_SCK_2      25  /*   2 kHz */
+#define ISP_SCK_4      26  /*   4 kHz */
+#define ISP_SCK_8      27  /*   8 kHz */
+#define ISP_SCK_16     28  /*  16 kHz */
+#define ISP_SCK_32     29  /*  32 kHz */
+/* hardware ISP modes */		       
+#define ISP_SCK_93_75  30  /*  93.75 kHz */
+#define ISP_SCK_187_5  31  /* 187.5  kHz */
+#define ISP_SCK_375    32  /* 375 kHz   */
+#define ISP_SCK_750    33  /* 750 kHz   */
+#define ISP_SCK_1500   34  /* 1.5 MHz   */
+
+
+/* last speed mode index */
+#define ISP_SCK_FIRST  ISP_SCK_0_5
+#define ISP_SCK_LAST   ISP_SCK_1500 
+
 #define ISP_DELAY 1
-#define ISP_SCK_SLOW 0
-#define ISP_SCK_FAST 1
+#define ISP_SCK_SLOW ISP_SCK_8 
+#define ISP_SCK_FAST ISP_SCK_375
+
+
 
 /* Prepare connection to target device */
 void ispConnect();
diff -ur usbasp.2007-10-23/firmware/main.c usbasp.2007-10-23-new/firmware/main.c
--- usbasp.2007-10-23/firmware/main.c	2007-10-23 13:14:02.000000000 +0300
+++ usbasp.2007-10-23-new/firmware/main.c	2008-03-29 21:08:47.000000000 +0200
@@ -63,11 +63,16 @@
 
   if(data[1] == USBASP_FUNC_CONNECT){
 
-    /* set SCK speed */
-    if ((PINC & (1 << PC2)) == 0) {
-      ispSetSCKOption(ISP_SCK_SLOW);
+    if (data[2] && data[2] >= ISP_SCK_FIRST && data[2] <= ISP_SCK_LAST) {
+      /* use speed index if there's valid one */
+      ispSetSCKOption(data[2]);
     } else {
-      ispSetSCKOption(ISP_SCK_FAST);
+      /* set SCK speed based on jumper */
+      if ((PINC & (1 << PC2)) == 0) {
+	ispSetSCKOption(ISP_SCK_SLOW);
+      } else {
+	ispSetSCKOption(ISP_SCK_FAST);
+      }
     }
 
     /* set compatibility mode of address delivering */