Is slow mem needed for A500 1MB emulation?

[rsn8887]

Is slow memory really needed for A500 1MB emulation? Or should fast mem be used? Is there any A500 1MB game that requires slow mem, or do all games also work with fast?

[Toni Wilen]

Yes. There are games that assume "slow ram" exists and will crash if it isn't there.. Also use of fast ram (instead of "slow ram") might break some games because it is "too fast" compared to slow ram which has chip ram speed.

[Matt_H]

It's worth noting, though, that out of all the games released for the Amiga the number requiring slow RAM is fairly small. And there are software workarounds, too: Degrader, WHDLoad, etc.

[Toni Wilen]

Originally Posted by Matt_H

It's worth noting, though, that out of all the games released for the Amiga the number requiring slow RAM is fairly small. And there are software workarounds, too: Degrader, WHDLoad, etc.

No software will help with autobooting floppies that directly access slow ram without caring if it exists or not. (Which is almost certainly what OP asked, 1M A500 is not very useful whdload config..)

[Galahad/FLT]

Lots of games "out of the box" assume slow ram at $c00000, and will simply not work without it.

Most games at the start of the 1Meg revolution assumed slow ram above chip ram and real fast ram.

Also, lots of crappy memory detection routines don't work properly, but will with slow ram.

Sure, lots of this stuff can be fixed, but simply having slow ram means you're covered, and its not like its expensive anymore!

[Foebane]

Is Slow RAM the same speed as Chip RAM?

If it is, then it's not a problem as the vanilla A1200 has no Fast RAM.

I just figured that Slow RAM was just that, RAM which is literally slower than the other types of RAM on Amiga.

[Rotareneg]

It's the worst of both worlds: It can't be used by the OCS chipset and yet the CPU still gets locked out of it during any DMA activity.

[rsn8887]

Interesting. I am asking because I observed gfx glitches in Lionheart Level 10 (horizontal riding level) on MiSTer Minimig using A500 with slow mem, but they went away with fast mem instead.

The cool thing about playing Lionheart with A500 + Fast Mem: You get much fewer slow downs in the game, and also you have none of that screen-tearing and water gfx glitches that plague the game on A1200 (even on real hardware, even on WHDLoad).

Then I wondered if I should just always enable fast instead of slow mem.

[DamienD]

Lionheart is a special case as it runs on virtually all Amiga models.

Take a look at the box: http://hol.abime.net/894/boxscan

In my collection I set an "A600 / Full ECS / 2MB Chip RAM" config

[lesta_smsc]

Originally Posted by rsn8887

Interesting. I am asking because I observed gfx glitches in Lionheart Level 10 (horizontal riding level) on MiSTer Minimig using A500 with slow mem, but they went away with fast mem instead.

The cool thing about playing Lionheart with A500 + Fast Mem: You get much fewer slow downs in the game, and also you have none of that screen-tearing and water gfx glitches that plague the game on A1200 (even on real hardware, even on WHDLoad).

Then I wondered if I should just always enable fast instead of slow mem.

On my A600 I think there was a very slight slow down during a scene where you moved into a lot of 'screen activity'. I just accepted that's how it was... but saying that you never noticed on A500+ makes me wonder why I did now lol.

[rsn8887]

I meant „Amiga 500 with Fast Mem“ not A500+. Sorry for the confusion.

[redblade]

Originally Posted by Galahad/FLT

Lots of games "out of the box" assume slow ram at $c00000, and will simply not work without it.

Most games at the start of the 1Meg revolution assumed slow ram above chip ram and real fast ram.

Also, lots of crappy memory detection routines don't work properly, but will with slow ram.

Sure, lots of this stuff can be fixed, but simply having slow ram means you're covered, and its not like its expensive anymore!

Galahad were all these checks just on the boot block or were some in the loader that got read by the boot block?

And can you remember if these stopped once the A500+ was released?

Thanks

[Galahad/FLT]

Originally Posted by redblade

Galahad were all these checks just on the boot block or were some in the loader that got read by the boot block?

And can you remember if these stopped once the A500+ was released?

Thanks

No, a lot of the ones that failed were ones that specifically use the system to detect memory types.

The majority of the ones that failed would write a longword into a memory type they were looking to detect, and then check if that longword had been written correctly.

Problem is, different Amigas mirrored memory not quite the same, so if you tried to detect memory at $200000, what they would do is write the longword to $200100, then clear address $100 (for the wraparound effect), and then compare if the longword was actually at $200100, if the memory type wasn't, it would be stored in $100.

But as Amigas progressed, this didn't always work.

The majority of the ones that worked used the system in the boot routine to detect memory type, and they usually got it right.

Of course even then there was the infamous Probe Software memory detection routine that used the system but there was a fundamental bug in it so it didn't work properly with A1200 with real fast mem.

So no, memory routines didn't get magically better because of the A500+ because ECS Amigas already had 1meg of chip ram, so from a memory perspective, the A500+ was no different.


Coding styles changed once 68020 was a major factor in Amiga games consideratio, no more processor timed stepper routines in loaders being the first fix.