OSDev.org

This is a spinoff of the BSOD thread which becomes slightly off-topic.

Yeah, I'm an Amiga fan, too. I had an Amiga 500.

It had some cool features, like
- Paul(a), Denis(e), Agnus/Agnes which are 3 specialized chips EDIT: and Copper and Blitter.
- could set the colour of the off-screen monitor colour (probably only Amiga users understand what I mean)
- extra-large diskettes (Same physical 3.5 inch floppy disks but more capacity.) [This has the unlucky side-effect that you can't read an Amiga floppy on a PC.]
- permit() and forbid(), 2 cool multitasking control syscalls
- Basic onboard (BTW from Microsoft If I remember correctly.) Back then I thought of C as uncool. Hah!
- the ability to boot from the diskette. (Demos...!)

Viewing back from now I can't understand why we, the Amiga users, hated the Atari ST so much. (And vice versa.) It was a cool computer, too. Probably we were victims of the marketing guys.

Back then I already thought "I would love to write an operating system or kernel for the Amiga"...

I wonder if AROS supports forbid() and permit().

Best Amiga greetings
Peter

The Amiga didn't have Basic onboard, as many other computers of the era did (including the PC); indeed it didn't have an onboard operating system. Amiga OS did include a Microsoft Basic interpreter. But for any serious programming C (or assembler) was the language of choice.

iansjack wrote:The Amiga didn't have Basic onboard, as many other computers of the era did (including the PC); indeed it didn't have an onboard operating system. Amiga OS did include a Microsoft Basic interpreter. But for any serious programming C (or assembler) was the language of choice.

It DID have an OS onboard.
And yes, C was the language of choice. I just failed to notice that back then.

Greetings
Peter

I guess it depends upon what you mean by an operating system. It had an operating system (Kickstart) in the same way that the IBM PC had an operating system (BIOS). You could actually use the PC without any further software; try turning an Amiga on with no disks in the drives (or no hard disk).

iansjack wrote:I guess it depends upon what you mean by an operating system. It had an operating system (Kickstart) in the same way that the IBM PC had an operating system (BIOS). You could actually use the PC without any further software; try turning an Amiga on with no disks in the drives (or no hard disk).

Yes, you are right!
In my memory you didn't need a disk to boot the multitasking OS. But when I read the wikipedia articles, I see there was an OS part on the ROM (Kickstart) and a part on a disk (Workbench). My memory played tricks on me.

EDIT: And now I remember the hand with the disk on the screen...

Greetings
Peter

PeterX wrote:Yeah, I'm an Amiga fan, too. I had an Amiga 500.

It had some cool features, like
- Paul(a), Denis(e), Agnus/Agnes which are 3 specialized chips EDIT: and Copper and Blitter.

Atari 800 had POKEY - sound serial & game controllers; ANTIC - DMA & part of graphics; CTIA or GTIA - remaining graphics; and something else too. You know that Amiga feature where you could split the screen and have different graphics modes at the same time, one above the other? Atari 800 could do that every line, if you were crazy enough.

PeterX wrote:- could set the colour of the off-screen monitor colour (probably only Amiga users understand what I mean)

Atari 800 can do too.

PeterX wrote:- extra-large diskettes (Same physical 3.5 inch floppy disks but more capacity.) [This has the unlucky side-effect that you can't read an Amiga floppy on a PC.]

Atari 800 disks are sadly tiny, but they're on what amounts to a primitive USB. Every peripheral on the serial bus used the same protocol, except for the tape drive.

BTW, can you read Amiga floppies on Macs? Macs had a variable-speed drive to get more capacity.

PeterX wrote:- permit() and forbid(), 2 cool multitasking control syscalls

Atari 800 didn't multitask, but it was only an 8-bit. There has been at least one multitasking GUI OS made for it in recent years, though.

PeterX wrote:- Basic onboard (BTW from Microsoft If I remember correctly.) Back then I thought of C as uncool. Hah!

I see that's been corrected, but anyway, the Atari 800 didn't have BASIC onboard either. In fact, the BASIC cartridge it came with was rather poor... because Atari had used too much ROM space implementing a very fancy OS for an 8-bit! It had a unified device interface very close to "everything is a file". It was closely tied to the proto-USB serial port, but also worked just fine for keyboard and screen. It had a small text editor as a built-in device; I was astonished when Linux didn't have anything like that.

PeterX wrote:- the ability to boot from the diskette. (Demos...!)

What machine can't do this? Atari 800 certainly can.

The really big down side to the Atari 800 was that it was launched 3 years prior to the Commodore 64, and thus had to conform to much more stringent FCC regulations. It thus had to be expensive, and every part of it was made up to match the price, including the OS and the peripherals. They never did manage to get the peripherals down to a reasonable price, probably because the proto-USB required every peripheral have a microcontroler inside. If you had a disk drive, a printer, and a RS-232 port, I think you had more microcontrollers on the bus than an IBM PC of the era had in total. Of course, a PC printer probably had a microcontroller too; I might need to rethink this...

PeterX wrote:Viewing back from now I can't understand why we, the Amiga users, hated the Atari ST so much. (And vice versa.) It was a cool computer, too. Probably we were victims of the marketing guys.

I remember the rivalry, but I think you Amiga owners had good reason to feel superior. The Atari ST was a much simpler device, especially graphically. What actually happened was Atari were working with a chipset manufacturer called Amiga Inc to design their upcoming 16-bit computer. Amiga Inc. broke off the deal & went to Commodore, getting 5 times the money and the bonus of not having to deal with the awful Jack Tramiel who was in charge of Atari at the time. I'm sure the ST was a rush job so Atari wouldn't look like they were lagging behind. (Its MIDI ports were good, though.) Speaking of rivalry, I used to be angry with Amiga Inc. I calmed down when I learned just how unpleasant Jack Tramiel could be. Even his obituary brought it up! Atari did better with the Falcon, fitting it with hardware DSP, but PC clones were dominant by the time it came out.

eekee wrote:It had a small text editor as a built-in device; I was astonished when Linux didn't have anything like that.

"ed(1) is the standard text editor."

Schol-R-LEA wrote:

eekee wrote:It had a small text editor as a built-in device; I was astonished when Linux didn't have anything like that.

"ed(1) is the standard text editor."

So why can't I use ed to copy stuff from the manual page to the shell prompt? Actually, what you could do with Atari's E: device was list a line of BASIC code, change it, and enter the changed code. It was flawed in some ways, but it was way ahead of ed which requires you to retype lines or concentrate on the regexp required to change only what you need.

eekee wrote:You know that Amiga feature where you could split the screen and have different graphics modes at the same time, one above the other? Atari 800 could do that every line, if you were crazy enough.

Yeah, I remember that feature

eekee wrote:BTW, can you read Amiga floppies on Macs? Macs had a variable-speed drive to get more capacity.

Dunno, but I guess yes! At least older Apples. Modern Apples' hardware is more close to PC in most ways, I think.

eekee wrote:

PeterX wrote:- Basic onboard (BTW from Microsoft If I remember correctly.) Back then I thought of C as uncool. Hah!

I see that's been corrected...

Yes, you both are probably right. Basic had to be bought and installed. I probably mixed that up with my VIC-20 with had Basic built-in.

eekee wrote:

PeterX wrote:- the ability to boot from the diskette. (Demos...!)

What machine can't do this? Atari 800 certainly can.

OK, I must admit that's pretty normal. There may have been some obscure systems which couldn't boot from diskette, but finding and listing them is pointless. Most systems can boot from diskette.

eekee wrote:

PeterX wrote:Viewing back from now I can't understand why we, the Amiga users, hated the Atari ST so much. (And vice versa.) It was a cool computer, too. Probably we were victims of the marketing guys.

I remember the rivalry, but I think you Amiga owners had good reason to feel superior. The Atari ST was a much simpler device, especially graphically.

But the ST had MIDI ready built-in. Amiga users had to buy it as an extra.

eekee wrote:The really big down side to the Atari 800 was that it was launched 3 years prior to the Commodore 64, and thus had to conform to much more stringent FCC regulations. It thus had to be expensive, and every part of it was made up to match the price, including the OS and the peripherals.

I don't know anything about FCC regulations. What did they claim?

Greetings
Peter

PeterX wrote:

eekee wrote:

PeterX wrote:- the ability to boot from the diskette. (Demos...!)

What machine can't do this? Atari 800 certainly can.

OK, I must admit that's pretty normal. There may have been some obscure systems which couldn't boot from diskette, but finding and listing them is pointless. Most systems can boot from diskette.

Yeah. Probably the very cheapest computers couldn't.

PeterX wrote:But the ST had MIDI ready built-in. Amiga users had to buy it as an extra.

The MIDI was good, yes, but technically it's just a serial port and doesn't even have different speeds. The Amiga's graphics modes - or even the Atari 800's - need a lot more silicon.

PeterX wrote:

eekee wrote:The really big down side to the Atari 800 was that it was launched 3 years prior to the Commodore 64, and thus had to conform to much more stringent FCC regulations. It thus had to be expensive, and every part of it was made up to match the price, including the OS and the peripherals.

I don't know anything about FCC regulations. What did they claim?

I don't remember exactly, beyond what you can read on the back labels of any 80s electronics, but the 1981 rules were much less demanding than previous rules. The Atari 800 had chunky cast metal shielding where later computers could get away with thin pressed plate which didn't even cover the whole board. I remember the 80s rules expected devices to accept interference. I think the earlier rules required they be shielded against any interference.

It is actually possible to read Amiga disks on a PC with a couple of disk drives and the appropriate software: http://www.oldskool.org/disk2fdi/

The greatest feature -- which kept Amiga in the market long after Commodore croaked -- was the Expansion Port, which routed all the necessary signals to have newer CPUs on expansion boards.

I owned an Amiga 1200 -- original CPU was an MC 68EC020 @ 14 MHz, original 2 MByte RAM -- which, eventually, ended up being powered by an expansion board sporting...

• a MC 68060 @ 50 MHz,
• a PPC 603e @ 240 MHz as "coprocessor",
• 256 MByte RAM,
• a Permedia II GPU with 4 MByte RAM,
• a FastSCSI controller.

Other extensions included a soundcard with a DSP capable of playing MP3's without CPU involvement plus a quad-ISDN-rate serial port plugged into what was referred to as a "clock port", and an ethernet card in the PCMCIA port. Plus a 2-GByte 2,5" hard drive.

All in the original case, which at first glance looked deceptively like an A500.

At one point someone addressed me, pointing to the computer I had tucked under my arm: "Hey, an Amiga! I once had one of those myself." I replied, "I highly doubt you had one of these."

R.I.P., A1200. I still miss 'ya.

I still have my A1200 (although only with a 68030 expansion card) sitting in a cupboard. I must dig it out and fire it up again some day. Although, TBH, it's easier just to run AmigaForEver.

@iansjack: I can find my Ataris, but they won't run. Probably PSU trouble, but the PSU is a sealed unit.

@Solar: I'm feeling retroactive envy right now! Having said that...

Solar wrote:original CPU was an MC 68EC020 @ 14 MHz

68020 seems respectable, but the Atari ST was clocked faster: 16MHz. :3

Didn't the 68020 have an MMU? Why did AmigaOS continue to not use it? Maybe I shouldn't ask when I'm not planning to use it, but hey!

eekee wrote:Didn't the 68020 have an MMU? Why did AmigaOS continue to not use it? Maybe I shouldn't ask when I'm not planning to use it, but hey!

By 'original', Solar is referring to the Amiga 1200 model, as opposed to the add-on upgrade he used. The original Amiga - which was retroactively dubbed 'Amiga 1000' later - and the Amiga 500 used the earlier 68000.

And now, a history lesson. You can skip the rest of this if you like, but you might find it interesting.

The 68000 (designed in 1979) had no memory management unit, and no support for virtual memory in any other form; according to Wikipedia, it had a hook for an MMU co-processor, and it could use the 68451 MMU to implement memory protection, but a flaw in the original design made it unusable for virtual memory. This was only learned later when the 68451 was actually designed.

The 68010 fixed the virtual memory problem and a few others which made the 68K problematic for certain high-end uses, and the 68451 MMU, which was originally meant for the 68K, was released primarily to go with it. However, the 68010 was still expensive when most of the systems using the 68K - the Lisa, Macintosh, Amiga, and Atari ST, among others - fixed their designs, and more importantly, none of them saw either memory protection or virtual memory as priorities. Several Unix workstations, most notably the Sun-2, did use a 68010 with a 68451, but it simply was seen as an expensive and unnecessary addition for the consumer market systems.

Note that both of these were 16/24/32 CPUs, with a 32-bit internal data size but only using 24 bits of a given register for addressing; the external buss pins had 16 data lines and 24 address lines on the packaging. This isn't directly relevant, but it does show that - just as with the segmentation in the 8086 - the package size (especially for the DIP form factor which was still nigh-universal) was seen as being as much of a priority as the memory capacity, if not more so.

When the 68020 was being designed (around 1982, roughly the same period when the 80186 and 80286 were released, but before design on the 80386 had really begun), they had moved to a Pin Grid Array packaging to allow them to make the jump to a true 32-bit bus, but on-chip MMUs weren't seen as being feasible yet given the die sizes and photolithographic processes of the time (this was also why on-chip FPUs didn't start appearing on commercial microprocessors until around 1989). Thus, they introduced an upgraded external MMU, the 68851.

By the time of its release in 1984, however, both Intel and Acorn were working on the problem, and the ARM250 (the 'high performance' version of the ARM2, used on upscale models of the original Archimedes) and 80386 were among the first CPUs to have an on-chip MMU (though other delays with the development of the Archimedes meant that the Acorn CPUs - ownership of which was to soon be spun off into ARM Holdings Ltd. - didn't see release until 1987).

Motorola wouldn't catch up on this until the '030 in 1987, by which time the Mac, Amiga, and Atari ST all had a growing software base which any future OS which did use the MMU would have to accommodate - and all of these parties had already had to do something similar already with the move to the 68020, since they needed to ensure that the software was '32-bit clean' to avoid conflicts with the change to the bus size. It would be years before any of them got around to implementing MMU support, and it had to remain an extra rather than a core feature given the number of older systems which were still in use.

By the time use of the MMU was gaining momentum among the operating system developers, the Motorola chip line was itself pretty much at the end of its lifespan, since after 1991 Motorola had fully committed to their part in PowerPC production after the disastrous delays in the release of the 68040. They didn't want to commit much effort into the last design of that series, the 68060, which was developed mainly to fulfill outstanding commitments.