From 2cd7fe716d3969a4ca071db6ac24058646a4d5ba Mon Sep 17 00:00:00 2001
From: OBattler <oubattler@gmail.com>
Date: Tue, 7 Nov 2023 06:34:04 +0100
Subject: [PATCH] The SiS 4xx chipset now no longer allow modifying the RAM
 amount bits of register 0x00, fixes #2306.

---
 src/chipset/sis_85c4xx.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/chipset/sis_85c4xx.c b/src/chipset/sis_85c4xx.c
index 97c989b73..cf4ff42d7 100644
--- a/src/chipset/sis_85c4xx.c
+++ b/src/chipset/sis_85c4xx.c
@@ -176,6 +176,8 @@ sis_85c4xx_out(uint16_t port, uint8_t val, void *priv)
                 valxor = val ^ dev->regs[rel_reg];
                 if (rel_reg == 0x19)
                     dev->regs[rel_reg] &= ~val;
+                else if (rel_reg == 0x00)
+                    dev->regs[rel_reg] = (dev->regs[rel_reg] & 0x1f) | (val & 0xe0);
                 else
                     dev->regs[rel_reg] = val;