Amiga questions you've always been too embarrassed to ask

[demolition]

It is called artistic freedom.

I used to have a couple of Beolab 3 and it is not possible to tilt them backwards like they show on this picture:
http://gordonkelly.com/wp-content/up...beolab3-pc.jpg

They can only be tilted like that if there are no cables connected.. Again, it looks nice on a picture but it is not possible or practical in real life.

Edit: If you wanted the speakers to function in that picture, I think you'd have to drill holes in the table below each speaker for the cables..

[losso]

A lot of boot block intros use the "root block" field at the very start of the disk…

-------------------------------------------------------------------------------
offset	size    number	name		meaning
-------------------------------------------------------------------------------
0/0x00  char    4       DiskType	'D''O''S' + flags
4/0x04  ulong   1       Chksum          special block checksum
8/0x08  ulong   1       Rootblock       Value is 880 for DD and HD 
...
-------------------------------------------------------------------------------

…for anything but the root block number (mostly signatures etc.; I try using it to store $dff000 and save 2 bytes by doing "move.l -x(pc),a6" instead of "lea $dff000,a6").

But: The disk images with these boot blocks still load perfectly, without any disk validation warning or anything. It seems like the root block value is ignored (or at least: ignored if it is way off).

So, I was just wondering, in case somebody is familiar with the way dos.library handles this: Does the root block value matter anywhere, or just under specific conditions?

[ransom1122]

1. In Dopus Can I hold down SHIFT to select multiple files from START to END selecting 50 files without selecting CTR+A?

2. If i want to make one huge HDF File with all my WHDLoad games and Demos, how big should the HDF File be, and can it be created with WINUAE if so how? for example 6gb HDF, winuae add hardfile / CREATE 6000MB?

Reason why I ask is I created a 5GB HDF and starting putting whdlaod games in the 5gb hdf, and the HDF was full only after finishing games #,A & B? Games were unzipped & Unrarred as File & FOlder structure in the HDF? I think I am only getting 1gb (Shown in Dopus) when i created the 5gb hdf? No idea??

[daxb]

2: You may reach the 2 or 4 GB file limit? Check what your filesystem limitations are.

[Daedalus]

Some applications also can't deal with the size calculations of large partitions, and that sounds like what's happening. Assuming your filesystem etc. is all set up to be large drive capable, if the version of DOpus you're using to copy everything doesn't support large drives, it will think the drive is full when it has 4GB left. When it gets to that point, using Workbench to add a few files to the drive will bring the available space just under 4GB, which should then work fine with DOpus again.

Applications that don't support large partitions calculate space as a 32-bit number, which means it's a maximum of 4GB. After that, the number wraps around to 0 and keeps going. So, a partition with 5GB of space will show up as 1GB free, 6GB as 2GB free, and so on. At some point during all your unpacking, you've used 1GB of space, and DOpus thinks there's only e.g. 1MB of space left, when in reality there's 4GB+1MB of space available.

[Vot]

Originally Posted by Daedalus

Some applications also can't deal with the size calculations of large partitions, and that sounds like what's happening. Assuming your filesystem etc. is all set up to be large drive capable, if the version of DOpus you're using to copy everything doesn't support large drives, it will think the drive is full when it has 4GB left. When it gets to that point, using Workbench to add a few files to the drive will bring the available space just under 4GB, which should then work fine with DOpus again.



Applications that don't support large partitions calculate space as a 32-bit number, which means it's a maximum of 4GB. After that, the number wraps around to 0 and keeps going. So, a partition with 5GB of space will show up as 1GB free, 6GB as 2GB free, and so on. At some point during all your unpacking, you've used 1GB of space, and DOpus thinks there's only e.g. 1MB of space left, when in reality there's 4GB+1MB of space available.

I don't like your answer.

You have explained it so clearly someone mentally impaired could follow your answer.

[Muzkat]

Here's one I always wanted to ask.

I recall reading somewhere that an Amiga 500 / Amiga monitor could display up to 4096 colors. It was a big selling point back in the day.

If this is the case, then why the constant obsession with 16 colors? Obviously it's a hardware restraint, but the two numbers have never reconciled well with me.

Can someone please explain?

[s2325]

I had slideshow with 4096 colors photos for ECS/OCS. I think you can display these images but not move them like objects in games. And it was blinking interlace. Most Amiga games had 32 colors, 16 had ST.

[demolition]

4096 colors is done using HAM mode: https://en.wikipedia.org/wiki/Hold-And-Modify
It is quite memory intensive and not well suited for animations and games in general. So for most games, 16 colors was the sweet spot for getting decent looking gfx without using too much RAM and disk space while being able to move things around.

For example, I don't think it is possible to do 50 Hz full screen updates (like you normally want from a smooth game) on a plain A500 in HAM mode and probably not even 25 Hz.

[Predseda]

HAM (Hold And Modify) is a very problematic screenmode that is really difficult to maintain. Problem is that each pixel in a horizontal row has its colour partially dependent to its neigbour on left. In Amiga OCS palette you have 32 independent colours for use, each pixel in this palette can have exact specific colour of your choice, but in HAM there are different rules and the coulour of a specific pixel can not be controlled. So you can create static HAM pictures (that are not perfect), but if you would like to MOVE them, the result would be unpredictable colour mess.

[Anakirob]

I'm sure I've seen 50Hz HAM effects, like plasmas, in OCS demos before, more than once. Unfortunately I can't name any off the top of my head. But those effects don't really have much practical application other than to look pretty. Doing something like a game is obviously unworkable.

[Vot]

http://eab.abime.net/showthread.php?t=5973

[slaapliedje]

I wonder if we could see something like this on an Amiga 500? http://www.atari.8bitchip.info/movpst.php That's probably one of the most impressive things I've seen an Atari STe do. The original ST had Spectrum 512 that could show 512 colors on screen as well, probably very similar to the HAM mode. I think the tricks with those is the same as the movie player, where each line has a max of 16 colors, but it's mapped quickly enough to trick the eye, so they can have many more colors on screen.

[slaapliedje]

Originally Posted by Gerry

I would be afraid of possible damage, so I personally would avoid putting a monitor on top of an Amiga.


It's not a nice way of presentation - even for an Atari ST .

Ha, that picture even shows how terribly unbalanced that'd be. Even the LCD that I have didn't look like it'd sit very well on the back of my Falcon. The only models in the ST/Amiga ranges I'd stick a monitor on top of would be the Mega ST, Mega STe, TT030 and 1000, 2000, 3000, 4000 in the Amiga range. Those were structured to sit a monitor on top.

[s2325]

In Walker F1 is for easy mode, F3 for arcade but what should be under F2 key? Hard mode after finishing other mode?

[Muzkat]

Thanks for the replies everyone.

While I'm at it, I might as well ask something else.

What's a copper? And what's a...blitter?

I realise I can look this stuff up, but you guys explain things in layman terms. Not to mention it stimulates discussion.

[Jope]

Copper: simple processor that can put data in registers and wait for certain positions on the screen
http://amigadev.elowar.com/read/ADCD.../node0048.html

Blitter: a memory copying unit that can move blocks of memory around, optionally applying a mask so that you can copy for example a circular area instead of only a rectangle. The Amiga's blitter also has line drawing capabilities.
http://amigadev.elowar.com/read/ADCD.../node0119.html

[rare_j]

Why does adding a fast accelerator to an a1200 cause chip ram access to be slow?
Is it an oversight on the part of the accelerator designer or an unavoidable side effect?

Is it possible to have a fast accelerator and fast chipram access?

Which faster cpus are affected? Is a fast 020 also affected by this problem? Or is it more to do with board design? Is there a tool to measure chipram access speed?

[-Acid-]

Originally Posted by rare_j

Why does adding a fast accelerator to an a1200 cause chip ram access to be slow?

I think you are mixed up here.... chip ram access is slower because they are usually slower memory chips (80ns I think?) than most fast ram (50 to 70ns typically). Also fast ram can only be accessed by the cpu which is much quicker than when the cpu and custom chips are both accessing the chip ram at the same time.

I do believe the likes of SysInfo will measure ram speeds.

[Shadowfire]

It would depend on the accelerator. If it isn't running synchronously to the A1200's internal clocks, then they need to perform clock domain crossing, which typically adds wait states.