From 5e4b721e97bd178489c11215aa58e3401331e761 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sun, 16 Feb 2020 21:07:03 -0500
Subject: [PATCH] Updates Byte Drive implementation as per latest information.

---
 Machines/Oric/BD500.cpp | 66 +++++++----------------------------------
 1 file changed, 10 insertions(+), 56 deletions(-)

diff --git a/Machines/Oric/BD500.cpp b/Machines/Oric/BD500.cpp
index c4b9cd942..7daf3ab57 100644
--- a/Machines/Oric/BD500.cpp
+++ b/Machines/Oric/BD500.cpp
@@ -10,6 +10,13 @@
 
 using namespace Oric;
 
+/*
+	Notes on the code below: the Byte Drive 500 isn't well documented; this implementation is based on
+	experimentation without access to real hardware as documented in http://forum.defence-force.org/viewtopic.php?f=25&t=2055
+	and with additional guidance from iss of Oricutron (amongst other things) elsewhere,
+	e.g. http://forum.defence-force.org/viewtopic.php?f=22&t=1698&start=105#p21468
+*/
+
 BD500::BD500() : DiskController(P1793, 9000000, Storage::Disk::Drive::ReadyType::ShugartModifiedRDY) {
 	disable_basic_rom_ = true;
 	select_paged_item();
@@ -57,9 +64,10 @@ void BD500::access(int address) {
 		case 0x0320: case 0x0321: case 0x0322: case 0x0323: case 0x0312:
 		return;
 
-		case 0x310:	enable_overlay_ram_ = true;		break;
+		case 0x311:	disable_basic_rom_ = true;		break;
 		case 0x313:	enable_overlay_ram_ = false;	break;
-		case 0x317:	disable_basic_rom_ = false;		break;		// Could be 0x311.
+		case 0x314:	enable_overlay_ram_ = true;		break;
+		case 0x317:	disable_basic_rom_ = false;		break;
 
 		default:
 //			printf("Switch %04x???\n", address);
@@ -69,60 +77,6 @@ void BD500::access(int address) {
 	select_paged_item();
 }
 
-/*
-	The following was used when trying to find appropriate soft switch locations. It is preserved
-	as the values I have above are unlikely to be wholly correct and further research might be
-	desirable.
-
-void BD500::access(int address) {
-	//	0,1,4,5,10,11 -> 64kb Atmos
-	//	2,3,9 -> 56kb Atmos.
-	// Broken: 6, 7, 8
-
-	int order = 5;
-	int commands[4];
-	std::vector<int> available_commands = {0, 1, 2, 3};
-	const int modulos[] = {6, 2, 1, 1};
-
-	for(int c = 0; c < 4; ++c) {
-		const int index = order / modulos[c];
-		commands[c] = available_commands[size_t(index)];
-		available_commands.erase(available_commands.begin() + index);
-		order %= modulos[c];
-	}
-
-
-	// Determine whether to perform a command.
-	int index = -1;
-	switch(address) {
-		case 0x0320: case 0x0321: case 0x0322: case 0x0323: case 0x0312:
-		return;
-
-		case 0x310: index = 0; break;
-		case 0x313: index = 1; break;
-		case 0x314: index = 2; break;
-		case 0x317: index = 3; break;
-
-		default:
-			printf("Switch %04x???\n", address);
-		break;
-	}
-
-	select_paged_item();
-
-	if(index >= 0) {
-		switch(commands[index]) {
-			case 0:	enable_overlay_ram_ = true;		break;		// +RAM
-			case 1: disable_basic_rom_ = false;		break;		// -rom
-			case 2: disable_basic_rom_ = true;		break;		// +rom
-			case 3:	enable_overlay_ram_ = false;	break;		// -RAM
-
-		}
-		select_paged_item();
-	}
-}
-*/
-
 void BD500::set_head_load_request(bool head_load) {
 	// Turn all motors on or off; if off then unload the head instantly.
 	is_loading_head_ |= head_load;