Minimum requirements for AmigaOS 4

[Daedalus]

I vaguely remember it being along the lines of:

128MB RAM (Fast RAM - you only need chip RAM if you wanna use the classic chipset)
AGA is the minimum chipset required, but I'll bet that's painful to use. I dunno what support is like for classic graphics cards...
A supported PPC CPU (these started at 160MHz on the Blizzard PPC I think)
A few GB of hard drive space and an optical drive
ROM / EEPROM? Not necessary. Kickstart is loaded into RAM from the hard drive during boot.

[Daedalus]

Significantly more than the 4 MB requirement for AmigaOS 3.

Seems the culture of keeping things slim went out of the window.

Not really sure what you're looking for here. If you stripped it down to the level of functionality of OS3 then it wouldn't need anywhere near 128MB (and yes, I think 128 was recommended - it'll boot in 64 as someone else said). But then why bother with OS4 at all? And, for the record, OS3 (as in 3.0 and 3.1) would happily boot in 1MB.

There are a few modest eye-candy additions in OS4, but most of the memory footprint is pretty legitimate, and it can be reduced by stripping out modules if you're that way inclined. For example, the Kickstart supports a much broader range of hardware, including graphics cards and USB, and so has greatly outgrown the original 512KB ROM. Since the Kickstart is loaded into RAM, there's more memory used already than OS3 needed to boot. Then the larger screenmodes eat memory - a 32-bit 1600x1200 screen takes almost 100 times the memory that a 16-colour 640x256 desktop takes. Then take the integrated TCP/IP stack, new filesystems with much larger buffers for modern drives, CD-ROM support from Kickstart and so on. I think these are all quite legitimate uses of extra memory, and couldn't be considered bloat... It's probably as slimline as you get while still supporting the features it has, and I haven't checked it out, but probably compares well to a Linux distribution with a similar range of support.

I have still to find the CPU that will load anything from any disc storage by itself. Ie, all computers have some kind of startup "ROM". The only thing close is some ARM CPUs that has a circa 2 kB builtin ROM that will serially download code from I2S based EEPROM.

Sorry, I didn't think you were looking for those sort of specs, since it's never an issue. I don't think Windows lists a BIOS as a requirement either... Basically, any machine that an OS4 licence is available for has the required ROMs. On a classic it can be bootstrapped from the classic OS, so whatever Kickstart is in that machine is all you need. Not sure what size UBoot is but it's available for download for some of the platforms so that would give you an idea.

[Daedalus]

Yup, that's what I was talking about. It's easy to strip modules out on AmigaOS4 and have a minimal boot. Bit I don't think anyone's documented a minimum booting machine requirement. The 64MB minimum is based on having all these things loaded. I don't know how low you could go, but it would be much less than 64MB.  But modules in Kickstart memory for hardware you don't have aren't used and don't consume "running" resources, so the only waste there is, is in the image of Kickstart itself.

If you're really worried about the 4MB or so that you'd save, it's a trivial task to comment out the Kickstart modules for hardware you don't have.

Personally though, I like having all my hardware available from boot. My OS3 machine does and takes far, far more than 4MB to boot to Workbench...

[Daedalus]

I guess, if you really need to be miserly with resources in this age of GHz and GB... But how does the OS know about the CD drive if it doesn't load drivers for it? Do you have to tell it to load it when you want to read a disc, and tell it when you don't wanna read it any more? Likewise for USB - with no stack running, you'd never know a device was plugged in unless you manually start the stack.

[Daedalus]

Errm - hot plug?

How do you think hot plug works? The OS needs to be told that something is plugged in. And how would it know that if there wasn't a USB stack running in the background? Say you plug in an external hard drive. The USB stack detects it, identifies it as mass storage and loads the appropriate driver. This driver identifies the geometry and then mounts the drive as a volume. That doesn't happen until you plug in a device, but the USB stack still has to be running to be able to see the hot plug event. That's pretty much as efficient as you can make it, without disabling the stack itself and thus removing hot plug capability.

Edit: Sorry, I thought you were talking to me - were you talking to freqmax there?

@freqmax

@Daedalus, Easy, load the driver, probe, save result. As for USB load the USB bus driver but treat other sub-drivers like the first one.

Load the driver, probe, save the result... That's pretty much what OS4 does though. You can plug several CD-ROM drives into an OS4 machine, but it'll only load drivers for the ones which are connected. If you don't have a 2 CD drives connected, it won't load two drivers. I don't understand your point there...

Just because there are resources isn't a good reason to waste them. One example is embedded usage where less resources saves equipment and battery etc..

That's very true, and as someone who writes firmware for embedded devices, I'm well aware of resource management issues there. But again, I don't see what's being wasted here with OS4. It only loads what it needs, but the powers that be have decided that modern features are needed...

@commodorejohn
Well, waste depends on your perspective. Most of the features are a little more advanced than OS3.9, and so take up more RAM. On top of that, it's all rewritten in C, which is bigger and less efficient, but means easier development. How much RAM does a 3.9 machine with USB, TCP/IP, and all the patches that would bring it to similar functionality use? I know mine uses a sizeable chunk of RAM, and I wouldn't get much change from 32MB... I guess one needs to decide if the OS should use more modern features, or stick with the old-fashioned, bolt-on-what-you-want philosophy...

[Daedalus]

@commodorejohn

I get what you're saying. OS4 is quite easily stripped out - as simple as commenting lines in a text file if you wanted to boot without things like USB or CD-ROM support. I don't condone bloating at all, which is one of the reasons I like Amiga-ish systems. I just think that an OS which is written for bloody expensive machines, can probably expect to have a reasonable minimum amount of RAM thrown at it too...

As a check, my OS4 machine uses about 100MB at boot, but includes lots of things at startup like SAMBA, SMBFS mounts, a dozen or more commodities, lots of disk caches, and a 1600x1200x32 composited Workbench.