Slow Ram and Chip ram options about vamigaweb

[Vweber73]

What I understand it that true fast ram needs to be on a separate Zorro 2 bus, which is much more expensive than the dumb trapdoor expansion... What is silly is to have limited the Agnus to 512k in the first place, it was nothing to have the address lines to adress 2Mb from scratch, there would never have been slow ram, the worse of both worlds, no speed, and not accessible by the chipset !

[mithrendal]

I tried but the core won't let me ... the vAmiga core does a plausible check and prevents the mem options you propose ... I could patch the core but maybe we first ask @dirkwhoffmann why this is like it is ...

[Vweber73]

It's not a big issue actually, the existing memory options are enough to run every single piece of software in optimal conditions :)
It was just for the sake of completeness, since these options indeed existed (like the 1.8mb trapdoor expansion, or the possibility to use the 512K only A501 expansion with A500+/A600).
Thanks and cheers

[mithrendal]

https://github.com/vAmigaWeb/vAmigaWeb/blob/main/Emulator/Memory/Memory.cpp

the constraints are in this file of the vAmigaCore lib ...

[Vweber73]

Thanks. Looks very much hardcoded !

[mithrendal]

Added units next to the numbers i.e. KB pushed it out

[Vweber73]

Thanks !

[dirkwhoffmann]

Now vAmiga supports SlowRam up to 1.5 MB. 1.8 MB is not supported, because SlowRam larger than 1.5 MB cover memory page $D8 and above. This is the place where older Amigas map the real-time clock.

[Vweber73]

Many thanks ! Yes, 1.8mb slow ram is an odd config, which I know existed but have never seen in real life...
What about 1.5mb chip ? This setting existed (A500+ with A501 instead of A501+).
Cheers

[dirkwhoffmann]

What about 1.5mb chip

Sticking to powers 2 (512 MB, 1024 MB, 2048 MB) makes emulation a bit easier and faster. E.g., I can handle memory mirroring via a bit mask instead of a modulo operation.

[Vweber73]

Understood.

My main motive to be flexible with the amount of Chip/Slow RAM was to test the minimum specs a game needs to have with full enhancements.
Exemple: Rise of the Dragon absolutely needs 1MB Chip to set the detail level to "high", no way around it. This rules out unmodified A500s. But interestingly enough, even though the manual says the same thing for Heart of China and Willy Beamish (2 similar games from the same publisher), 512K chip + 1MB slow or fast is enough to have full enhancements !

Anyway for such tests, you current options are enough: even though some games may exist for which 1Mb chip is not enough for the full Monty but 1.5Mb (not 2Mb) would be, these games would be from 1993 or later, and by that time, only having a A500+ with a 512k A501 (not A501+) would have been very odd, 2MB chip was an easy option by then !

As for slow memory, 1.5mb is enough, that makes it 2Mb total without fast ram, enough to test any game that would require only 512k chip but more memory of any kind for enhancements.

[mithrendal]

why did commodore sold slow ram expansions anyway ? makes no sense to me... Maybe an engineer at commodore did an error when designing A501 ... no?

[mithrendal]

Much more expensive? How much? Did they have to pay licenses on zorro?

[Vweber73]

I don't know, but I think it needed separate hardware. The A590 which had up to 2Mb fast ram was as expensive as the A500 itself... The A2000 with Z2 bus was much more expensive than the A500, and the bus was about the only hardware difference with the A500... On the other hand the A501 512k expansion was a cheap device, that everybody ended up buying, allowing for 1Mb games, which the Atari 520ST did not easily allow...

[Vweber73]

Anyway, is it possible to have 1mb and 1.5mb added as slow ram options in vAmigaWeb, since they are now possible in vAmiga ?
Many thanks and cheers