From: disean <di.sean@protonmail.com>
Date: Tue, 14 Jan 2020 17:47:36 +0000 (+0600)
Subject: [HAL][FREELDR] Fix system timer oscillator frequency on a Xbox (#2245)
X-Git-Tag: 0.4.14-RC~755
X-Git-Url: https://git.reactos.org/?p=reactos.git;a=commitdiff_plain;h=e5c00524662f1396a889411fd7dfa81403121de7

[HAL][FREELDR] Fix system timer oscillator frequency on a Xbox (#2245)

See https://xboxdevwiki.net/Porting_an_Operating_System_to_the_Xbox_HOWTO#Timer_Frequency
---

diff --git a/boot/freeldr/freeldr/arch/i386/hardware.c b/boot/freeldr/freeldr/arch/i386/hardware.c
index 0cac33d4986..67074c0fd30 100644
--- a/boot/freeldr/freeldr/arch/i386/hardware.c
+++ b/boot/freeldr/freeldr/arch/i386/hardware.c
@@ -27,8 +27,13 @@ DBG_DEFAULT_CHANNEL(HWDETECT);
 #define MILLISEC     (10)
 #define PRECISION    (8)
 
+#if defined(SARCH_XBOX)
+#define CLOCK_TICK_RATE 1125000
+#else
+#define CLOCK_TICK_RATE 1193182
+#endif
+
 #define HZ (100)
-#define CLOCK_TICK_RATE (1193182)
 #define LATCH (CLOCK_TICK_RATE / HZ)
 
 static unsigned int delay_count = 1;
diff --git a/hal/halx86/include/halp.h b/hal/halx86/include/halp.h
index 9c03a96f43d..0ef52df2a93 100644
--- a/hal/halx86/include/halp.h
+++ b/hal/halx86/include/halp.h
@@ -86,11 +86,18 @@ VOID
 //
 #define GRAPHICS_MODE_12 0x12           /* 80x30	 8x16  640x480	 16/256K */
 
+#if defined(SARCH_XBOX)
+//
+// For some unknown reason the PIT of the Xbox is fixed at 1.125000 MHz,
+// which is ~5.7% lower than on the PC.
+//
+#define PIT_FREQUENCY 1125000
+#else
 //
 // Commonly stated as being 1.19318MHz
 //
 // See ISA System Architecture 3rd Edition (Tom Shanley, Don Anderson, John Swindle)
-// P. 471
+// p. 471
 //
 // However, the true value is closer to 1.19318181[...]81MHz since this is 1/3rd
 // of the NTSC color subcarrier frequency which runs at 3.57954545[...]45MHz.
@@ -104,6 +111,7 @@ VOID
 // number is quite long.
 //
 #define PIT_FREQUENCY 1193182
+#endif
 
 //
 // These ports are controlled by the i8254 Programmable Interrupt Timer (PIT)