[hatari-devel] IMP chipset (in)compatibility

[Christian Zietz <czietz@xxxxxxx>]

Hello,

over in a German forum [1], a user wondered why two games (G-Loc and
Team Suzuki) wouldn't run on his (real) MegaST. And he was able to
confirm this with Hatari: Runs on emulated ST, doesn't run on emulated
MegaST.

Wild theories were discussed (regarding Blitter and RTC), but in the
end, this turned out to be a chipset issue, both in Hatari as in the
real HW. I checked both games: they reset the (STE-only) 'linewidth'
register $FF820E/FF820F. This is harmless on an ST/MegaST with Ricoh
chipset but causes a bus error on an IMP chipset, as confirmed by your
tests:

https://git.tuxfamily.org/hatari/hatari.git/tree/tests/buserror/results/st_w.txt
(Ricoh)
https://git.tuxfamily.org/hatari/hatari.git/tree/tests/buserror/results/mst4_w.txt
(IMP)

This explains the user's observation, as Hatari emulates the MegaST with
an IMP chipset, but the ST with a Ricoh chipset. Furthermore, the user
confirms that his real MegaST indeed has an IMP chipset. Note that I'm
therefore *not* saying Hatari is wrong here (you had to make a choice).
 I'm proposing a patch (attached) to compatibility.html.

Regards
Christian

[1]
<https://forum.atari-home.de/index.php/topic,16426.msg255046.html#msg255046>
--
Christian Zietz  -  CHZ-Soft  -  czietz@xxxxxxx
WWW: https://www.chzsoft.de/
PGP/GnuPG-Key-ID: 0x52CB97F66DA025CA / 0x6DA025CA

From 693df1c6a16e755a069583b0ac42a5240b346eb2 Mon Sep 17 00:00:00 2001
From: Christian Zietz <czietz@xxxxxxx>
Date: Wed, 10 Mar 2021 20:09:52 +0100
Subject: [PATCH] Add note about G-Loc and Team Suzuki

---
 doc/compatibility.html | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/doc/compatibility.html b/doc/compatibility.html
index 84483a01..4a108184 100644
--- a/doc/compatibility.html
+++ b/doc/compatibility.html
@@ -265,6 +265,11 @@ are also listed.</p>
 	  not correctly initialized to play digidrums. Use STE mode instead.</td>
     </tr>
     <tr>
+      <td><a href="http://www.atarimania.com/game-atari-st-g-loc_20968.html";>G-Loc</a></td>
+      <td>2.3.1</td>
+      <td>Incompatible with IMP chipset used for MegaST emulation. Set machine type to ST or STE instead.</td>
+    </tr>
+    <tr>
       <td><a href="http://www.atarimania.com/game-atari-st-garfield-winter-s-tail_9415.html";>Garfield Winter's Tail</a></td>
       <td>1.8</td>
       <td>Requires TOS &le; 1.04 and &le; 1MB RAM. Does not work with cartridge / HD emulation</td>
@@ -463,6 +468,11 @@ are also listed.</p>
           fails to load</td>
     </tr>
     <tr>
+      <td><a href="http://www.atarimania.com/game-atari-st-team-suzuki_10483.html";>Team Suzuki</a></td>
+      <td>2.3.1</td>
+      <td>Incompatible with IMP chipset used for MegaST emulation. Set machine type to ST or STE instead.</td>
+    </tr>
+    <tr>
       <td>The Deep</td>
       <td>1.1</td>
       <td>When running on Hatari versions before 1.6, the RS232 emulation must
-- 
2.11.0