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How Amiga 500 RAM Probably Works

62 points| doener | 4 years ago |youtube.com

30 comments

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[+] egypturnash|4 years ago|reply
I’m skimming over the transcript and this dude is all “well most games didn’t take advantage of anything beyond 512K so what use was it” and, well, we did use the damn things for stuff beyond games back in the day, you know.

Games are the part that’s most interesting for retrocomputing and nostalgia; I played a lot of games on my Amigas, but I also did stuff like “laid out the newsletter for the local Dr Who fan club” and “chatted on BBSs” and “dabbled with art and animation” and all of those things were enhanced by having more than the bare minimum of RAM. Hell, I connected it to the Internet by getting a PPP gateway up on a mainframe at the local university and browsed the Web, that sure was helped by extra RAM.

[+] daggersandscars|4 years ago|reply
> we did use the damn things for stuff beyond games back in the day, you know.

This. The Amiga's multitasking was amazing back in the mid/late 1980s. My favorite example:

I'm in my dorm room, writing a paper in a non-western-alphabet language[1] on my Amiga. The phone rings. My BBS, running in the background, answers the phone and someone logs in. This all happens with zero impact on my using the computer.

This blew my fellow students' minds. I'd have to show the BBS user's activity for them to believe me. All this on a machine with only floppy disks. I couldn't afford a hard drive until later.

I also wrote solvers for math problems in AmigaBASIC, fancier programs in Modula 2 (I couldn't afford the C compiler), and, of course, played games.

Edited to add [1]

----

[1] There was one PC that supported this. Not having to sign up to use it made getting homework done much easier.

[+] vidarh|4 years ago|reply
Exactly - The 512K expansions were by far the most common expansion. I did play games on my Amiga, but far more of my time was spent doing other things with it.
[+] ud_0|4 years ago|reply
If you make a game for a given platform, it makes sense to target the most common configuration, which in this case was 512k (not 512M btw). Even though RAM expansions eventually became popular, I guess publishers would be hesitant to put a "requires 1M+" sticker on their boxes. But man, 512k seemed like a blessing in those early days, too...
[+] xbar|4 years ago|reply
k. Not M, right?
[+] rasz|4 years ago|reply
He almost gets it right. The switch doesnt move trapdoor Ram to the other side of the bus buffers, it merely changes how Amiga chipsets see it.
[+] icedchai|4 years ago|reply
My A500 was tricked out with 3 megs of RAM. 512k onboard + 512k trapdoor + 2 megs on the expansion bus. This was incredible for 1990.
[+] xbar|4 years ago|reply
This is very good comedy, and I'm merely an Amiga bystander.
[+] progre|4 years ago|reply
I enjoyed the stab at Atari ST far too much - apparently that grudge has lasted well over 30 years.
[+] YesThatTom2|4 years ago|reply
What’s great about this video is that all the jokes have their basis in truth… usually an uncomfortable truth.
[+] justinlloyd|4 years ago|reply
Ex Amiga and Atari ST programmer. C Compiler, games, BBS doors, databases, and a few other things published.

There were many games that worked beyond 512K, Prince of Persia being a notable one, and I think DungeonMaster by FTL being another. I started on the A500 but eventually acquired an Amiga workstation with 8MB RAM, a 68030 CPU and a 120MB HDD that was an absolutely stunning development system for the time. I also had a couple of A500s on the desk, in various configurations, to make sure the code I wrote would work on other machines. And a dedicated A2000 running the BBS with a 1GB HDD. I'd code on the x30 equipped Amiga, and download via parallel cable to the A500 for testing.

The interesting thing about Amiga RAM layout was that there was Chip RAM and Fast RAM and RAM. Chip RAM was accessible by both CPU and dedicated video/sound chips. I am going to get a bit fuzzy on the remembered details, but the CPU accessed the RAM on the rising clock and the chips accessed the RAM on the falling clock - I'd have to verify if that was the correct way around. Fast RAM on the Zorro bus or in the Sidecar was only accessible by CPU, so it had full bandwidth access. I recall the trapdoor RAM expansions was often slower, not just because of the shared bus but also many manufacturers just used the cheapest/slowest RAM they could source.

I recall the ECS could access RAM up to 1MB, maybe even more, it's been 30+ years. I wrote functions to detect if the computer had Fast RAM installed and if so, relocate the code above 512KB for a speed boost, and also, in the case of a compiler, put a small "RAM disk" above 512KB to cache data.

Original Atari ST was interesting for other reasons beyond the chipset of the Amiga, mainly the peripheral support, the not worrying about RAM layout, the higher resolution displays (oh my god those high rez grey scale displays). Also I could wire up my ST to my Yamaha DX7 and run Cubase. My first ST development system was the 260 ST with the ROM BIOS on a dongle on the left hand side, which I had to send back (the entire machine) to Atari for replacement when they finally released the 520 ST to developers. Years later I was kicking myself for having sent the machine back because there was less than 1,000 of the 260 ST developer units made and it was a piece of history. And then through a strange confluence of events, almost 25 years later, I was wandering around WeirdStuff several years before it closed and there, on the shelf, for ten bucks, was the 260 ST with my initials on it.

I liked programming the Atari ST for "just get on with it", in that it was you, the CPU, and the display output, and it was a pretty straight line between the two. On the Amiga, you often had to think in "parallel" parts and timings, so it was a different mindset. It wasn't harder or easier, it was just different. I enjoyed developing for both for different reasons.

[+] dusted|4 years ago|reply
The humour in this is excellent!