What does softkick actually mean?

[Sim085]

I have an A500+ with the original Kickstart 2.04 it came with. I have software version of both Kickstart 1.3 and 3.1 which I loaded from original using GrabKick. I want to keep Kickstart 2.04 physically installed and load software load on Kickstart 1.3 or 3.1 on top of Kickstart 2.04 (or instead).

Is softkick what I need?

If so how does it work? and does it work on every Amiga model or do I need some special hardware (MMU).

[thomas]

Yes, I think softkick is the word which describes all these methods. Other words are MapROM or FastROM which describe special cases.

What all these methods do is to reserve RAM, as much as is needed to load the ROM image into it, load it and then fool the system to think the ROM is now in that RAM area.

Normally you need an MMU or an accelerator with MapROM support to do this. These two methods work with any ROM version. They use a method very similar to virtual memory: when the CPU accesses an address inside the ROM area, they translate the address to the corresponding address in the mapped RAM area. The CPU does not even notice.

An accelerator with MapROM has a little mini-MMU just for this purpose. A real MMU is a multi-purpose memory manager which in this case is used to do the same little memory management.

On Aminet there is a software called skick. I think there are others, too. It works without an MMU. But it has its limits. The major limit is that it only works with known ROM images. Because it cannot translate addresses in hardware, it has to relocate absolute addresses in the ROM to the new location. In order to do this it has to know where in the ROM are absolute addresses. This information is in the .PAT and .RTB files which come with skick. For a new ROM version one would have to create new corresponding .PAT and .RTB files, which usually is a huge amount of manual work.

Another limit is that it cannot protect the mapped ROM. With an MMU or a mini-MapROM-MMU, the mapped ROM area can be protected against write accesses once it has been established. Without an MMU this is not possible.

All these methods have in common that they eat up as much RAM as is needed for the ROM image. For a Kick 3.1 image this is 512 KB. So if you have an unexpanded A500+ with just 1 MB RAM, then skick will eat up one half of all your RAM.

[Sim085]

Thank you for the details explanation. To be honest if I do this I will also have some 2MB FastRAM (as part of the side expansion) so I would not mind loosing 512KB.

I would guess this would also increase load times as the Amiga would first need to boot from the installed kickstart and then re-load the wanted one? or it does not work like that?

[daxb]

It depends but usually yes. If the ROM file is loaded from disk to RAM then a reset is needed. After a soft reset the ROM is still resident in RAM and boot time should be fast as usually. After a hard reset the ROM in RAM is "killed" and it need to load again with reset.

There exists hardware like ACA500 (I guess) that can hold different ROMs in flash memory to be used. This should be also fast. Then there are accelerator cards like thomas mentioned.

[thomas]

On the other hand, if your FastRAM is faster than the Kickstart ROM, then you could notice an overall speed increase of system-friendly software.

That's why one variant of the various softkick methods is called FastROM.

[admiral]

I use mkick very reliably with a kick34 (1.3) A500.

Systems with 2.x roms do also have other options, such as skick.

Kickstart is loaded into ram (typically order of preference is fast, slow then chip, and it tends to go to the end of it), with relocations, and the system reboots. At ColdCapture or CoolCapture, some code by the softkicker does the switch from one kickstart to the other.

No MMU is needed, but some newer softkickers (like blizkick, for blizzard cards with support for some others) do support or require a MMU.

My open source amigaXfer tool can dump roms through the serial, should you need to dump another computers' rom for the purpose of softkicking or emulation. It can also do very fast file and floppy transfers.