Encode result block scales as OCP E8M0

PyGolden/mxcore_gemm_functions.py

@@ -309,6 +309,7 @@ def pack_uint8_to_lines(byte_list):
                     nan_byte = 0x7D if data_type != "FP8ALT" else 0x7F
                     if poisoned and block_poison_enable:
                         quantized_all = [nan_byte] * len(block_fp32)
+                        scale = 0xFF
                     else:
                         quantized_all = [quantize_fn(v, scale) for v in block_fp32]
                     mx_row_segments.append((quantized_all[:q_cols], scale))
@@ -498,14 +499,15 @@ def write_to_c_header(fp9_matrix_a, fp9_matrix_b, scale_matrix_a, scale_matrix_b
                     segment = [_acc_to_fp32_u32(result_matrix[row_idx][col_start + q_start + j]) for j in range(q_cols)]
                     block_fp32 = segment + [0] * (result_mx_block_size - q_cols)
                     scale, poisoned = block_scale(block_fp32, data_type="FP8ALT" if data_type == "FP8ALT" else "FP8")
-                    result_scale_mx.append(scale)
                     quantize_fn = quantize_e5m2 if data_type != "FP8ALT" else quantize_e4m3
                     nan_byte = 0x7D if data_type != "FP8ALT" else 0x7F
                     if poisoned and block_poison_enable:
                         quantized_all = [nan_byte] * len(block_fp32)
+                        scale = 0xFF
                     else:
                         quantized_all = [quantize_fn(v, scale) for v in block_fp32]
                     result_mx_all.extend(quantized_all[:q_cols])
+                    result_scale_mx.append(scale)
 
     # Pack bytes into memory_data_width words
     bytes_per_word = memory_data_width // 8

PyGolden/mxcore_utils.py

@@ -18,9 +18,6 @@ def bin32_to_float(s32):  # "01000000101000000000000000000000" -> 5.0
     b = int(s32[-32:], 2)
     return struct.unpack('!f', struct.pack('!I', b))[0]
 
-def to_signed8(x):
-    return x - 256 if x > 127 else x
-
 def vec_to_hex(vec, vector_size=8, memory_data_width=32):
     """
     Converts a vector of binary strings into hex memory lines (padded mode).
@@ -178,13 +175,7 @@ def block_scale(block, data_type="FP8"):
         emax = 15 if data_type == "FP8" else 8
         max_exp = max([(fp32_to_fields(x)[1]) for x in block])
         is_special = any((fp32_to_fields(x)[1] == 0xFF) for x in block)
-        scaled = max_exp - (127 + emax)
-        scale_emax = 127
-        if scaled > scale_emax:
-            return scale_emax & 0xFF, True
-        if scaled < -scale_emax:
-            return (-scale_emax) & 0xFF, is_special
-        return scaled & 0xFF, is_special
+        return max(max_exp - emax, 0), is_special
 
 def _quantize_mxfp8(fp32_val, scale, mant_bits, exp_bits, bias, exp_max, exp_min, sat_byte, nan_byte, full_field_reserved):
     sign, exp, mant = fp32_to_fields(fp32_val)
@@ -199,7 +190,7 @@ def _quantize_mxfp8(fp32_val, scale, mant_bits, exp_bits, bias, exp_max, exp_min
     is_subnorm_in = (exp == 0)
     unbiased_exp = (1 - 127) if is_subnorm_in else (exp - 127)
     full_mant = mant if is_subnorm_in else ((1 << 23) | mant)
-    scaled_exp = unbiased_exp - to_signed8(scale)
+    scaled_exp = unbiased_exp - (scale - 127)
 
     if scaled_exp > exp_max:
         return (sign << 7) | sat_byte

mxcore-rtl/src/hwpe/block_scale.sv

@@ -19,13 +19,10 @@ module block_scale #(
   output logic                        block_poison_o
 );
 
-  localparam int FP32_BIAS  = 127;
   localparam int E5M2_EMAX  = 15;
   localparam int E4M3_EMAX  = 8;
   localparam int MXFP8_EMAX = (Encoding == 0) ? E5M2_EMAX : E4M3_EMAX;
 
-  localparam int SCALE_EMAX = (2 ** (ScaleWidth-1)) - 1;
-
   // Number of Levels/Stages in the Comparator Tree
   localparam int STAGES     = $clog2(BlockSize);
 
@@ -41,8 +38,6 @@ module block_scale #(
 
   // Scaled Exponent
   logic signed [9:0]  scaled_exponent;
-  logic               scale_overflow;
-  logic               scale_underflow;
 
   // Comparator Tree Stages
   logic [STAGES:0][BlockSize-1:0][7:0]  stage;
@@ -71,14 +66,10 @@ module block_scale #(
   endgenerate
   assign max_exponent = stage[STAGES][0];
 
-  assign scaled_exponent  = $signed({2'b00, max_exponent}) - FP32_BIAS - MXFP8_EMAX;
-  assign scale_overflow   = scaled_exponent > SCALE_EMAX;
-  assign scale_underflow  = scaled_exponent < -SCALE_EMAX;
-
-  assign block_scale_o    = scale_overflow  ? ScaleWidth'(SCALE_EMAX) :
-                             scale_underflow ? ScaleWidth'(-SCALE_EMAX) :
-                             scaled_exponent[ScaleWidth-1:0];
+  // OCP E8M0 Scale (Bias 127)
+  assign scaled_exponent  = $signed({2'b00, max_exponent}) - MXFP8_EMAX;
+  assign block_scale_o    = (scaled_exponent < 0) ? '0 : scaled_exponent[ScaleWidth-1:0];
 
-  assign block_poison_o   = scale_overflow || (|is_special);
+  assign block_poison_o   = |is_special;
 
 endmodule : block_scale

mxcore-rtl/src/hwpe/fp32_to_mxfp8_quantizer.sv

@@ -84,7 +84,7 @@ module fp32_to_mxfp8_quantizer #(
     end else begin
       unbiased_exponent = is_input_subnorm ? (1 - FP32_BIAS) : (fp32_exponent - FP32_BIAS);
       full_mantissa     = is_input_subnorm ? {1'b0, fp32_mantissa} : {1'b1, fp32_mantissa};
-      scaled_exponent   = unbiased_exponent - $signed(scale_i);
+      scaled_exponent   = unbiased_exponent - ($signed({2'b00, scale_i}) - FP32_BIAS);
       // Overflow
       if (scaled_exponent > EXPONENT_MAX) begin
         mxfp8_exponent  = (Encoding == 0) ? ((Saturate == 1) ? 5'h1e : 5'h1f) : 4'hf;

mxcore-rtl/src/hwpe/mxcore_hwpe_result_quantizer.sv

@@ -77,7 +77,7 @@ module mxcore_hwpe_result_quantizer #(
   assign mxfp8_result_o.strb  = {(OutputDataWidth/8){1'b1}};
 
   assign mx_result_scale_o.valid = fp32_result_i.valid;
-  assign mx_result_scale_o.data  = block_scale;
+  assign mx_result_scale_o.data  = (block_poison && block_poison_i) ? '1 : block_scale;
   assign mx_result_scale_o.strb  = {ScaleWidth/8{1'b1}};
 
 endmodule : mxcore_hwpe_result_quantizer