[HN Gopher] The Amiga Story: Conceived at Atari, Born at Commodo...
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The Amiga Story: Conceived at Atari, Born at Commodore (2016)
Author : wslh
Score : 47 points
Date : 2022-10-08 14:45 UTC (8 hours ago)
(HTM) web link (lowendmac.com)
(TXT) w3m dump (lowendmac.com)
| MarkusWandel wrote:
| Technically it's not the blitter (a fast way to move bits around)
| that allowed the machine to have 4096 colours. All you need for
| that is 4-bit RGB DACs and appropriate colour lookup tables. And
| enough memory to store, say, 5 bitplanes (32 colour lookup table)
| at 320x200 = 40KB of memory, which up to this point had been
| prohibitively much, e.g. in a machine with only 64KB of memory.
| unwind wrote:
| Yeah, that part:
|
| _The Lorraine chipset was also very powerful. It took
| advantage of blitters, chips that allowed information to bypass
| the CPU completely. Thanks in part to the blitters on the
| mainboard, the machine was capable of displaying up to 4,096
| colors._
|
| Was really confused-sounding. The Amiga only had one blitter,
| and it was not a discrete chip (part of Agnus I think). The
| "bypassing" is probably a reference to the DMA that the custom
| chips used in order to work independently from the CPU.
|
| I grew up/learnt coding on the Amiga, loved it sooo much.
|
| Edit: copypasta fix.
| andoma wrote:
| Cut my teeth on the Amiga as well. Still have the Amiga
| Hardware Reference Manual in my bookshelf. Can't throw it out
| now? I was around 11-12 years old when I started to program
| on it. Certainly didn't understand some parts, in particular
| I remember the blitter's truth table [0] was confusing to me
| at the time. But it was a pang of nostalgia when I realized
| the new AVX-512 VPTERNLOGx [1] instructions uses the exact
| same table as the Amiga's blitter. Must be a perfect fit for
| Amiga emulators :)
|
| [0] https://wiki.amigaos.net/wiki/Graphics_Minterms [1]
| https://www.felixcloutier.com/x86/vpternlogd:vpternlogq
| acherion wrote:
| > Still have the Amiga Hardware Reference Manual in my
| bookshelf. Can't throw it out now?
|
| If you do decide to ever dispose of the book, please don't
| throw it away. Sell it so that this knowledge can be passed
| down to someone who wants to learn. Reprints of these kinds
| of books aren't being made anymore, and the only other
| knowledge source would be (rather old) programmers from the
| time, who aren't around forever.
| moosedev wrote:
| I also spent some of my formative technical years on the
| Amiga. The Amiga Hardware Reference Manual is available
| on archive.org for posterity:
| https://archive.org/details/amiga-hardware-reference-
| manual-...
|
| I support not throwing out a real, original copy, though
| :-)
|
| As I get older I enjoy reading 30+ year old technical
| books and learning more about how those old systems
| worked, more than I do learning the latest framework or
| language features. It's intrinsically satisfying, but not
| so great for the career...
| codeflo wrote:
| Maybe what's meant is that the blitter allowed the machine to
| practically deal with the amount of data that so many colors
| required. The C64 could display more colors in static images
| than in animated sprites.
| bitwize wrote:
| Well, you're right but kinda not right. The Amiga's design was
| really cohesive, and the blitter did help enable larger color
| output than would otherwise have been possible, in a kind of
| roundabout way.
|
| See, the RAM chips of the day were too slow to push out more
| than a few bits per pixel during scanout. The workaround for
| this was planar graphics modes, which allowed the video chip to
| receive color information from multiple RAM chips at the same
| time, each chip supplying one bit of the color data for the
| pixel. But in order to compose a display using the CPU, you had
| to use multiple blits -- one for each plane of the image -- and
| each time, if you wanted to blit to arbitrary locations, you
| would have to AND a mask onto the source image and then OR in
| the destination image because each plane has bits for 8 pixels
| packed into a single byte. This was possible on the PC, but
| slow; and PC planar graphics modes had 4bpp max. With 5bpp it
| would have been intolerable. (Really, planar graphics is a
| bitch; even the Amiga developers knew this, which is one reason
| why they put the Akiko chip in the Amiga CD32 to do chunky-to-
| planar conversions so programmers can write code assuming
| chunky.)
|
| One of the things the Amiga blitter handles is drawing bitmaps
| to arbitrary locations in planar graphics modes much faster
| than the CPU could do, enabling fast displays with more colors
| than other machines could handle.
|
| The real color magic on the Amiga, though, was Hold and Modify
| -- which allowed for all 4096 colors theoretically on screen at
| once within contemporary memory speed and size constraints, in
| a way that wouldn't have been prohibitively taxing without that
| special support.
| jcadam wrote:
| I still have my AmigaDOS reference manual on my bookshelf.
| Occasionally someone will recognize it in a zoom meeting.
| JeremyReimer wrote:
| The Amiga was (and still is!) an amazing machine.
|
| If you liked this article and would like to read more, I'll take
| this opportunity to plug my History of the Amiga series on Ars
| Technica: https://arstechnica.com/series/history-of-the-amiga/
| twsted wrote:
| Wonderful article, Jeremy, I have read it multiple times.
|
| Highly recommended.
| BashiBazouk wrote:
| My housemate had an Amiga 1000. Cool computer for the time and we
| played many a video game on it. One day the floppy drive died. We
| bought a compatible floppy drive and opened it up. There was a
| aluminum shield over the drive and most the components that
| required a large number of screws to remove. I've had easier
| times opening up a laptop to fix something than that pain in ass
| 1000...
| acherion wrote:
| Commodore took radio shielding rather seriously back then. The
| wedge Amigas (A500, A600 and A1200) also had excessive metal
| shielding everywhere. A lot of Amiga owners nowadays just
| dispose of that as it always gets in the way when you have to
| fix the next thing that breaks in these machines.
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