diff --git a/common/cputypes.h b/common/cputypes.h
index 8839f24ec..678f5792e 100644
--- a/common/cputypes.h
+++ b/common/cputypes.h
@@ -106,7 +106,9 @@
 #if defined(_WIN64)
   #define CLIENT_OS        OS_WIN64
   #define CLIENT_OS_NAME   "Win64"
-  #if defined(_M_AMD64)
+  #if defined(OPENCL)
+    #define CLIENT_CPU     CPU_OPENCL
+  #elif defined(_M_AMD64)
     #define CLIENT_CPU     CPU_AMD64
   #elif defined(_M_IA64)
     #define CLIENT_CPU     CPU_IA64
diff --git a/common/problem.cpp b/common/problem.cpp
index 2cda68d5c..728956762 100644
--- a/common/problem.cpp
+++ b/common/problem.cpp
@@ -86,8 +86,7 @@ static unsigned int __problem_counter = 0;
 */
 
 /* ------------------------------------------------------------------- */
-
-#if (SIZEOF_LONG == 8)  /* SIZEOF_LONG is defined in cputypes.h */
+#if (SIZEOF_LONG == 8 || (CLIENT_OS == OS_WIN64 && CLIENT_CPU == CPU_OPENCL))  /* SIZEOF_LONG is defined in cputypes.h */
 # include "pack8.h"
 #else
 # include "pack4.h"
diff --git a/makefile.vc b/makefile.vc
index 257e85911..78567dee2 100644
--- a/makefile.vc
+++ b/makefile.vc
@@ -7,7 +7,8 @@
 #PROCESSOR_ARCHITECTURE = AMD64
 #PROCESSOR_ARCHITECTURE = cuda
 #PROCESSOR_ARCHITECTURE = ATI_STREAM
-#PROCESSOR_ARCHITECTURE = OPENCL
+#PROCESSOR_ARCHITECTURE = OPENCL32
+#PROCESSOR_ARCHITECTURE = OPENCL64
 #PROCESSOR_ARCHITECTURE = arm
 
 BASENAME = dnetc
@@ -62,12 +63,18 @@ OPTS_M_PLAT = IX86
 CHIPSRCPATH = plat
 #CHIPSRCPATH = plat/$(PROCESSOR_ARCHITECTURE)
 ZIPSUFFIX = win32-x86-stream
-!elseif "$(PROCESSOR_ARCHITECTURE)" == "OPENCL"
+!elseif "$(PROCESSOR_ARCHITECTURE)" == "OPENCL32"
 HAVE_OGR_CORES = 0
 OPTS_CC_CPU =
 OPTS_M_PLAT = IX86
 CHIPSRCPATH = plat
 ZIPSUFFIX = win32-x86-opencl
+!elseif "$(PROCESSOR_ARCHITECTURE)" == "OPENCL64"
+HAVE_OGR_CORES = 0
+OPTS_CC_CPU =
+OPTS_M_PLAT = AMD64
+CHIPSRCPATH = plat
+ZIPSUFFIX = win64-amd64-opencl
 !elseif "$(PROCESSOR_ARCHITECTURE)" == "arm"
 HAVE_OGR_CORES = 0
 OPTS_CC_CPU = /D_ARM_WINAPI_PARTITION_DESKTOP_SDK_AVAILABLE=1
@@ -220,12 +227,18 @@ ZIPEXTRAS = $(ZIPEXTRAS) docs\readme.stream
 
 # OpenCL support
 
-!if "$(PROCESSOR_ARCHITECTURE)" == "OPENCL"
+!if "$(PROCESSOR_ARCHITECTURE)" == "OPENCL32"
 OPTS_MSVC = $(OPTS_MSVC) -I"$(OPENCLDIR)include" -Iplat\opencl -Iplat\x86
 OPTS_LIBS = $(OPTS_LIBS) "$(OPENCLDIR)lib\x86\OpenCL.lib"
 ZIPEXTRAS = $(ZIPEXTRAS) docs\readme.opencl
 !endif
 
+!if "$(PROCESSOR_ARCHITECTURE)" == "OPENCL64"
+OPTS_MSVC = $(OPTS_MSVC) -I"$(OPENCLDIR)include" -Iplat\opencl -Iplat\amd64
+OPTS_LIBS = $(OPTS_LIBS) "$(OPENCLDIR)lib\x86_64\opencl.lib"
+ZIPEXTRAS = $(ZIPEXTRAS) docs\readme.opencl
+!endif
+
 # --------------------------------------------
 
 all: $(BASENAME).exe $(BASENAME).com $(BASENAME).scr
@@ -406,7 +419,7 @@ RC5_72_OBJS =                             \
         $(OUTPUTPATH)/adl.obj        
 
 OPTS_MSVC = $(OPTS_MSVC) -DHAVE_RC5_72_CORES -DATI_STREAM -DDYN_TIMESLICE
-!elseif "$(PROCESSOR_ARCHITECTURE)" == "OPENCL"
+!elseif "$(PROCESSOR_ARCHITECTURE)" == "OPENCL32" || "$(PROCESSOR_ARCHITECTURE)" == "OPENCL64"
 RC5_72_OBJS =                      \
         $(OUTPUTPATH)/ocl_info.obj \
         $(OUTPUTPATH)/ocl_setup.obj \
@@ -599,7 +612,7 @@ $(VC_CHECK):
 {$(RC572SRCPATH)/stream}.cpp{$(OUTPUTPATH)}.obj::
         cl -c $(OPTS_MSVC) -Ox -Fo$(OUTPUTPATH)\ $<
 
-!elseif "$(PROCESSOR_ARCHITECTURE)" == "OPENCL"
+!elseif "$(PROCESSOR_ARCHITECTURE)" == "OPENCL32"
 
 {$(CHIPSRCPATH)/x86}.asm{$(OUTPUTPATH)}.obj:
         nasmw -o $(@:/=\) -f win32 -i $(CHIPSRCPATH:/=\) $(**:/=\)
@@ -613,6 +626,20 @@ $(VC_CHECK):
 {$(RC572SRCPATH)/opencl}.cpp{$(OUTPUTPATH)}.obj::
         cl -c -O2 $(OPTS_MSVC) -Fo$(OUTPUTPATH)\ $<
 
+!elseif "$(PROCESSOR_ARCHITECTURE)" == "OPENCL64"
+
+{$(CHIPSRCPATH)/amd64}.asm{$(OUTPUTPATH)}.obj:
+        nasmw -o $(@:/=\) -f win64 -i $(CHIPSRCPATH:/=\) $(**:/=\)
+
+{$(CHIPSRCPATH)/amd64}.cpp{$(OUTPUTPATH)}.obj::
+        cl -c $(OPTS_MSVC) -Ox -Fo$(OUTPUTPATH)\ $<
+
+{$(CHIPSRCPATH)/opencl}.cpp{$(OUTPUTPATH)}.obj::
+        cl -c $(OPTS_MSVC) -Ox -Fo$(OUTPUTPATH)\ $<
+
+{$(RC572SRCPATH)/opencl}.cpp{$(OUTPUTPATH)}.obj::
+        cl -c -O2 $(OPTS_MSVC) -Fo$(OUTPUTPATH)\ $<
+
 !elseif "$(PROCESSOR_ARCHITECTURE)" == "arm"
 
 {$(RC572SRCPATH)/arm}.asm{$(OUTPUTPATH)}.obj: