From 4fbaa047bb530c464e727c4b7940c24c36806938 Mon Sep 17 00:00:00 2001
From: FeralChild64 <you@example.com>
Date: Thu, 26 Dec 2019 22:27:58 +0100
Subject: [PATCH] optional faster DolphinDOS loop

---
 c64/,,config_custom.s                 |  3 +-
 c64/kernal/iec/load_iec.s             |  5 +--
 c64/kernal/iec_fast/load_dolphindos.s | 58 +++++++++++++++++++++++++--
 3 files changed, 58 insertions(+), 8 deletions(-)

diff --git a/c64/,,config_custom.s b/c64/,,config_custom.s
index c6eb3fa8..bbe3c239 100644
--- a/c64/,,config_custom.s
+++ b/c64/,,config_custom.s
@@ -46,7 +46,8 @@
 
 #define CONFIG_IEC
 #define CONFIG_IEC_BLANK_SCREEN
-#define CONFIG_IEC_DOLPHINDOS     // not finished yet, but LOAD works
+#define CONFIG_IEC_DOLPHINDOS      // not finished yet, but LOAD works
+#define CONFIG_IEC_DOLPHINDOS_FAST // needs more testing
 #define CONFIG_IEC_JIFFYDOS
 
 #define CONFIG_TAPE_NORMAL
diff --git a/c64/kernal/iec/load_iec.s b/c64/kernal/iec/load_iec.s
index 16031cc3..37f1271f 100644
--- a/c64/kernal/iec/load_iec.s
+++ b/c64/kernal/iec/load_iec.s
@@ -150,9 +150,8 @@ load_iec_loop:
 	plx_trash_a
 !:
 	// Check for EOI - if so, this was the last byte
-	lda IOSTATUS
-	and #K_STS_EOI
-	beq load_iec_loop
+	bit IOSTATUS
+	bvc load_iec_loop
 
 	// FALLTROUGH
 
diff --git a/c64/kernal/iec_fast/load_dolphindos.s b/c64/kernal/iec_fast/load_dolphindos.s
index 57e63820..f9315291 100644
--- a/c64/kernal/iec_fast/load_dolphindos.s
+++ b/c64/kernal/iec_fast/load_dolphindos.s
@@ -15,13 +15,24 @@ load_dolphindos:
 	// A trick to shorten EAL update time
 	ldy #$00
 
+#if CONFIG_IEC_DOLPHINDOS_FAST
+	// Another trick: prepare values for quickly setting/releasing DATA
+	lda CIA2_PRA
+	and #$FF - BIT_CIA2_PRA_DAT_OUT - BIT_CIA2_PRA_CLK_OUT - BIT_CIA2_PRA_ATN_OUT
+	sta IECPROTO                       // release DATA
+	ora #BIT_CIA2_PRA_DAT_OUT
+	sta TBTCNT                         // pull DATA
+#endif
+
 	// FALLTROUGH
 
 load_dolphindos_loop:
 
+#if !CONFIG_IEC_DOLPHINDOS_FAST
 	// Check if this was EOI
 	bit IOSTATUS
 	bvs load_dolphindos_end
+#endif
 
 	// Wait for the talker to release the CLK line
 !:
@@ -29,25 +40,60 @@ load_dolphindos_loop:
 	bvc !-
 
 	// Release the DATA to signal we are ready
+#if !CONFIG_IEC_DOLPHINDOS_FAST
 	lda CIA2_PRA
 	and #$FF - BIT_CIA2_PRA_DAT_OUT    // release
+#else
+	lda IECPROTO
+#endif
 	sta CIA2_PRA
 
-	// Wait till DATA line is released (someone else might be holding it)
+#if !CONFIG_IEC_DOLPHINDOS_FAST
+
+	// Check if EOI
+	jsr iec_rx_check_eoi               // can damage .X, but this is safe
+
+#else
+
+	// Check if EOI - inlined code to avoid wasting cycles on RTS
+	ldx #$13
 !:
 	bit CIA2_PRA
-	bpl !-
+	bvc load_dolphindos_no_eoi
+	dex
+    bne !-  
 
-	// Check if EOI - routine can damage .X, but this is safe
-	jsr iec_rx_check_eoi
+    // EOI - mark it and retrieve the last byte
+    jsr iec_rx_check_eoi_confirm
+	lda CIA2_PRB
+	sta (EAL),y
+
+	// Update EAL for the last time
+	sec
+	jsr iec_update_EAL_by_Y
+
+	// Restore proper IECPROTO value
+	lda #$02
+	sta IECPROTO
+
+	// End of load loop
+	jmp load_iec_loop_end
+
+load_dolphindos_no_eoi:
+
+#endif
 
 	// Retrieve and store byte
 	lda CIA2_PRB
 	sta (EAL),y
 
 	// Pull DATA to acknowledge
+#if !CONFIG_IEC_DOLPHINDOS_FAST
 	lda CIA2_PRA
 	ora #BIT_CIA2_PRA_DAT_OUT
+#else
+	lda TBTCNT
+#endif
 	sta CIA2_PRA
 
 	// Handle EAL
@@ -56,6 +102,8 @@ load_dolphindos_loop:
 	inc EAL+1
 	jmp load_dolphindos_loop
 
+#if !CONFIG_IEC_DOLPHINDOS_FAST
+
 load_dolphindos_end:
 
 	// Update EAL
@@ -65,5 +113,7 @@ load_dolphindos_end:
 	// End of load loop
 	jmp load_iec_loop_end
 
+#endif
+
 
 #endif // CONFIG_IEC_DOLPHINDOS and not CONFIG_MEMORY_MODEL_60K