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fatwizard
July 6th, 2016, 05:44 AM
Hello everyone. I have been having a blast playing with the Amiga 500 I recently acquired. The system works perfectly save for having to replace the internal floppy drive and replace the battery on the memory/clock expansion card. As I was looking thru some Amiga magazines, I notice an ad for Mindscape's "The Halley Project". This was always one of my very favorite games on my old Atari 800, and I was really looking forward to playing the Amiga version. Alas, I can't seem to find a disk image that will run on my Amiga. I have downloaded every copy I can find, but none of them will run on my machine.

I thought it might be an issue with the Gotek floppy drive emulator, so I removed the drive from the external floppy, and hooked it up as DF0: I made a disk for each ADF I had found, but I had the same results.

I am quite new to the Amiga, so I am wondering if I'm doing something wrong. The ads I saw for the program were from 1985, so I wasn't expecting compatibility issues with Workbench 1.2 which the system currently has. I have had quite a few game titles that won't run, but I thought it was because they were to new for my machine, or maybe they are all PAL versions.

I would just love to get this working if possible. Does anyone have experience with this program? Maybe someone with more experience with the Amiga might have some ideas about where I'm going wrong.

Thanks in advance.

A4000Bear
July 9th, 2016, 10:41 PM
I'm not familiar with that particular game, but it is quite common for very early Amiga games to not like any memory expansions.

Try removing the memory expansion card.

fatwizard
July 10th, 2016, 08:27 AM
Holy smoke rings A4000Bear! The memory expansion was the problem. I haven't tried all of the titles that wouldn't run yet, but so far it looks like this is the tip I was looking for. Thank you very much.

KC9UDX
July 10th, 2016, 08:33 AM
I always wondered why this is. What resource do all those games use that is alerted by the expansion card?

gonk23
July 10th, 2016, 05:34 PM
I always wondered why this is. What resource do all those games use that is alerted by the expansion card?

I believe data that is used by the custom chips normally needs to reside in chip RAM. The developer probably carelessly assumed all memory was chip RAM and therefore didn't specify the memory type when allocating the memory for certain items (e.g. sprites, audio, etc.) and the OS has inadvertently allocated memory in the expansion card (which isn't chip RAM unless you've made the appropriate mod to the A500) when running the program.

fatwizard
July 10th, 2016, 06:48 PM
I believe data that is used by the custom chips normally needs to reside in chip RAM. The developer probably carelessly assumed all memory was chip RAM and therefore didn't specify the memory type when allocating the memory for certain items (e.g. sprites, audio, etc.) and the OS has inadvertently allocated memory in the expansion card (which isn't chip RAM unless you've made the appropriate mod to the A500) when running the program.

Appropriate mod?

car88fan2
July 10th, 2016, 09:20 PM
Many Thunder Mountain games released for the C64 will check the I/O channel while loading and if it detects a cartridge (I.E. Fast Load, Memory Expansion) it will not load correctly. I'm sure Mindscape did this to on some games for the Amiga.

KC9UDX
July 10th, 2016, 09:35 PM
I believe data that is used by the custom chips normally needs to reside in chip RAM. The developer probably carelessly assumed all memory was chip RAM and therefore didn't specify the memory type when allocating the memory for certain items (e.g. sprites, audio, etc.) and the OS has inadvertently allocated memory in the expansion card (which isn't chip RAM unless you've made the appropriate mod to the A500) when running the program.

That's a good point, but, as I recall, mine was modified for 1M CHIP when I was having problems running games. It's been twenty years though so I might not recall correctly.

KC9UDX
July 10th, 2016, 09:38 PM
Appropriate mod?

Trap door RAM is normally configured as FAST RAM, even though it runs the same speed as CHIP RAM. The reason is that the A500 originally came with a 512k AGNUS. If you put in a 1M AGNUS, you can change some jumpers to make the expansion memory CHIP RAM. It seems to me you have to cut a trace and solder another.

gonk23
July 10th, 2016, 10:32 PM
Trap door RAM is normally configured as FAST RAM, even though it runs the same speed as CHIP RAM. The reason is that the A500 originally came with a 512k AGNUS. If you put in a 1M AGNUS, you can change some jumpers to make the expansion memory CHIP RAM. It seems to me you have to cut a trace and solder another.

Reference: http://aminet.net/docs/hard/500hacks.txt (see section iv)

As the document mentions, performing the mod on rev 6a motherboards is easier than rev 5 (and earlier) motherboards, and later rev 6a motherboards even came with the 1MB Agnus already installed (but still in the 512kB chip + 512kB fast configuration).

gonk23
July 10th, 2016, 10:46 PM
That's a good point, but, as I recall, mine was modified for 1M CHIP when I was having problems running games. It's been twenty years though so I might not recall correctly.

Yeah, I think there were many reasons poorly programmed software could fail.

* Kickstart version. Earlier games often needed KS1.2 or earlier. Most A500s shipped with KS1.3. The programmer was probably calling undocumented routines in KS1.2, etc.

* According to section iv-2 of http://aminet.net/docs/hard/500hacks.txt, performing the 1MB chip RAM mod would actually move the expansion memory from $C00000 to $80000 in the address map. Therefore if the careless developer assumed the expansion memory was always at $C00000, it would either crash or assume it was just an unexpanded 512kB machine. The author mentions some compatibility examples in section iv-3 of the same document.

Some people made the mod switchable, e.g.: http://www.vcfed.org/forum/showthread.php?8981-Amiga-500-F-C-switch-on-Side-Expansion-bay

fatwizard
July 12th, 2016, 03:03 PM
Looking around, I haven't found any software solutions for booting the system with expansion ram disabled. I have noticed that some ram expansion systems provided a switch to disable it. The Commodore A501 has no such provision. I'm wondering how veteran Amiga users deal with this issue. It is more than cumbersome to pull the A501 out for old games, and put it back in for other uses.

gonk23
July 12th, 2016, 06:49 PM
I have noticed that some ram expansion systems provided a switch to disable it. The Commodore A501 has no such provision.

I wouldn't be surprised if someone over the years has documented a switch hack for the A501 somewhere.


I'm wondering how veteran Amiga users deal with this issue. It is more than cumbersome to pull the A501 out for old games, and put it back in for other uses.

Back in the day I had a very similar configuration as yours, and that's exactly what I did when I wanted to play those games. Which normally meant I didn't play those games very much. However I only had a very small number of such games.

Now days my A500 has the 1MB chip RAM mod, KS2, a hard drive, and I use WHDLoad. WHDLoad loads the correct KS, patches any incompatibilities, etc so those older games can play.

jltursan
July 12th, 2016, 10:49 PM
I wouldn't be surprised if someone over the years has documented a switch hack for the A501 somewhere.

Not hard at all; but by far the easiest way is to install a special boot in a floppy with tools like Slow RAM on/off or DF1: on/off, that usually do the trick with a lot of incompatible games.

fatwizard
July 13th, 2016, 08:17 AM
Not hard at all; but by far the easiest way is to install a special boot in a floppy with tools like Slow RAM on/off or DF1: on/off, that usually do the trick with a lot of incompatible games.

It might be easy to do, but not so easy finding instructions to do it.

KC9UDX
July 13th, 2016, 06:13 PM
It might be easy to do, but not so easy finding instructions to do it.

It's not easy. It won't even work with any game that doesn't run within AmigaDOS.