From a3684545b5647a9fcfb824f71bccdcbb46809d59 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Thu, 6 Jul 2017 22:33:54 -0400
Subject: [PATCH] Added a block on the tape motor for a short period after each
 time the ROM routine is intercepted for a substituted byte read. To reduce
 the collision between fast tape and real tape loading.

---
 Machines/ZX8081/ZX8081.cpp | 14 ++++++++++++--
 Machines/ZX8081/ZX8081.hpp |  1 +
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/Machines/ZX8081/ZX8081.cpp b/Machines/ZX8081/ZX8081.cpp
index 7c18fa392..cf3c24ed0 100644
--- a/Machines/ZX8081/ZX8081.cpp
+++ b/Machines/ZX8081/ZX8081.cpp
@@ -22,7 +22,8 @@ Machine::Machine() :
 	hsync_(false),
 	nmi_is_enabled_(false),
 	tape_player_(ZX8081ClockRate),
-	use_fast_tape_hack_(false) {
+	use_fast_tape_hack_(false),
+	tape_advance_delay_(0) {
 	set_clock_rate(ZX8081ClockRate);
 	tape_player_.set_motor_control(true);
 	clear_all_keys();
@@ -53,7 +54,11 @@ int Machine::perform_machine_cycle(const CPU::Z80::PartialMachineCycle &cycle) {
 	}
 
 	if(is_zx81_) horizontal_counter_ %= 207;
-	if(!use_fast_tape_hack_) tape_player_.run_for_cycles(cycle.length);
+	if(!tape_advance_delay_) {
+		tape_player_.run_for_cycles(cycle.length);
+	} else {
+		tape_advance_delay_ = std::max(tape_advance_delay_ - cycle.length, 0);
+	}
 
 	if(nmi_is_enabled_ && !get_halt_line() && get_non_maskable_interrupt_line()) {
 		set_wait_line(true);
@@ -132,6 +137,11 @@ int Machine::perform_machine_cycle(const CPU::Z80::PartialMachineCycle &cycle) {
 					ram_[hl & ram_mask_] = (uint8_t)next_byte;
 					*cycle.value = 0x00;
 					set_value_of_register(CPU::Z80::Register::ProgramCounter, tape_return_address_ - 1);
+
+					// Assume that having read one byte quickly, we're probably going to be asked to read
+					// another shortly. Therefore, temporarily disable the tape motor for 1000 cycles in order
+					// to avoid fighting with real time. This is a stop-gap fix.
+					tape_advance_delay_ = 1000;
 					return 0;
 				} else {
 					tape_player_.get_tape()->seek(time);
diff --git a/Machines/ZX8081/ZX8081.hpp b/Machines/ZX8081/ZX8081.hpp
index 9bd9044a5..d07ed461a 100644
--- a/Machines/ZX8081/ZX8081.hpp
+++ b/Machines/ZX8081/ZX8081.hpp
@@ -94,6 +94,7 @@ class Machine:
 		uint8_t latched_video_byte_;
 
 		bool use_fast_tape_hack_;
+		int tape_advance_delay_;
 };
 
 }