Amiga questions you've always been too embarrassed to ask

[xArtx]

If the left mouse button is BFE101, what is the joystick fire button?

[jimbob]

Slow RAM, what's that all about? I gather it has all the drawbacks of chip and none of the benefits so what's it doing in the design? Any redeeming features?

Not exactly embarrassing but I've been wondering this for a while so I guess it fits here.

[TCD]

It was cheap

[jimbob]

Do you mean cheaper because you didn't have to buy a sidecar or CPU plug in board to get real fast? But that doesn't explain to me what it's doing in the design. If the chipset is controlling the memory access, why not make this address area real chip. If its not gonna be real chip, why not use the address area for real fast. Maybe something to do with the way Agnus put on weight, designers hedging there bets regarding compatibility with future chipsets?

[Toni Wilen]

Exactly, it was really cheap and simple to implement.

Fat Agnus, even the original 512k chip version, have 1M (or was it 2M?) external addressing capability. Internal DMA address counters are still limited to 512k (256k words). This limits chip RAM size.

Because Agnus have extra external address lines, upper 512k bank can be easily mapped to somewhere else just be rerouting Agnus' upper address pin. "Slow RAM" was born.

This design decision also made 1M Agnus pin compatible with old version (*). Which was really nice decision (I am sure 1M chip ram was planned long time ago but they didn't have resources to upgrade all Agnus internals until much later), upgrade Agnus, reroute upper address pin again and you have 1M chip RAM.

*) Technically it wasn't 100% pin compatible but it had nothing to do with chip ram addressing, they replaced TEST pin with PAL/NTSC selection pin.

[Mrs Beanbag]

Originally Posted by Jack Burton

Why the windows can't be moved past the borders on Amiga OS (like on some other OS that I forgot the name ) ? Was it a kind of limitation or because the guys simply didn't think about this feature ?

I don't know but I like that. Sometimes on Linux I manage to get a window's title bar off the top of the screen and can't get it back again.

[jPV]

Originally Posted by Jack Burton

Why the windows can't be moved past the borders on Amiga OS (like on some other OS that I forgot the name ) ? Was it a kind of limitation or because the guys simply didn't think about this feature ?

Might be technically easier? Or just traditionally not thought. But it can also be a design point. Many people still prefer that windows are restricted to screen area, it makes positioning of them easier if you want them to be visible all the time.

I for example use in my main OS (MorphOS) the same restriction even though it would allow the other option too. In practise I use more positioning of windows to borders than wanting them to go out. I have hotkey to allow it to work other way around, but rarely use it.

[Cymru]

As I recall the Slow Ram showed up with the first Fat Agnus (A1000 had none) and disappeared with the 1 MB Agnus -- one had to add memory to use a 2 MB chip; the Fattest Agnus (2 MB) took up all the Chip Ram address lines as noted above. It was Slow because the bus had to contend with the Agnus at the same time. One could speed it up by turning Agnus off (blanking the screen).

[Hewitson]

Originally Posted by Mrs Beanbag

I don't know but I like that. Sometimes on Linux I manage to get a window's title bar off the top of the screen and can't get it back again.

Holding ALT will allow you to move the window from inside it.

[Jack Burton]

@Mrs Beanbag
@jPV

Well, I think I have a bad habit that comes from the way I use M$ xp or 7. I usually have many programs and folder opened, making an intensive use of drag'n drop. So the screen is quickly filled with windows. That's why moving the windows past the borders of the screen can come in handy (it saves you from instant suffocation !). And then, that's probably why when I use my Amiga I have this claustrophobic feeling !

[Jack Burton]

I have another question.
I remember many years ago having read on a forum a post from a guy saying that the Amiga keyboard controller (he called it back then "keyboard cpu") had been used for matrix calculation on a Demo. It was in a thread about the way the hardware was implemented to ease the multitasking on the Amiga, and the unexpected way to use it. But since this story I never heard of such a thing again. I personally have some doubts about it, but maybe someone can confirm/invalidate it.

[Cymru]

I know that it does matrix decoding into a ASCII character sent over the serial interface, but I'm not sure it is a stand alone type CPU like the old IBM XT had that was an 8-bit CPU retasked to handle the keyboard alone.

[Steve T]

Originally Posted by Lord Aga

What the frell was this supposed to be:

Always wondered about this too, I realise there's no connector there and nothing developed for it, but could pins be added and something useful done with it? if so, what? Could you potentially add expansion boards this way?

I guess if it were worth doing then it would have already been done, though

[prowler]

Originally Posted by Steve T

Always wondered about this too, I realise there's no connector there and nothing developed for it, but could pins be added and something useful done with it? if so, what? Could you potentially add expansion boards this way?

I guess if it were worth doing then it would have already been done, though

That question has already been answered by demolition on the previous page.

Originally Posted by demolition

According to this, it belongs together with P9B which has the clock port pins. When they made the 1200, they weren't sure whether it should have 1 or 2MB chipmem, so the connector would be used in case it was born with 1MB to place a 1MB upgrade board. Since it ended up having 2MB, there was no use for the connector.

Maybe they opted for maximum realism? If I push papers off beyond the edges of my desk, they will fall to the floor.

[Steve T]

Originally Posted by prowler

That question has already been answered by demolition on the previous page.

Sure, sorry if my post wasn't clear, (and I apologise for breaking your forum quoting that enormous image) I'm not re-asking the same question I meant since there's no way it could be used to add more chipmem, what else could it be used for? I mean you could presumably add your own header (no i'm not prepared to experiment) would it then be like another clockport or something?

[roy bates]

i think it was just memory data path for chipram the other end was/is a clock port for rtc and addons for the clock port.

[xArtx]

They might have tested the motherboard with it's RAM on a daughter board
before soldering it on, because RAM is expensive.

[lifeschool]

Originally Posted by Jack Burton

Why the windows can't be moved past the borders on Amiga OS (like on some other OS that I forgot the name ) ? Was it a kind of limitation or because the guys simply didn't think about this feature ?

Go to Prefs, Screenmode prefs. Where it says screen width/height, click off 'default' and put in something like 1710 x 1566. Now you can drag your windows around off the edge of the visible window, and move the whole screen off the edge by holding the left Alt. key. This is only useful if you have different programs running on their own exclusive screens. May be a lazy workaround?

Question: why does turning on the audio filter make the power LED go dim?

[thomas]

Originally Posted by xArtx

If the left mouse button is BFE101, what is the joystick fire button?

BFE101 is the parallel port.

Fire/left button on the first game port is bit 6 of BFE001.
Fire/left button on the second game port is bit 7 of BFE001.

[thomas]

Originally Posted by lifeschool

Question: why does turning on the audio filter make the power LED go dim?

It doesn't. Turning it *off* dims the LED.

They just shortened the lines. Perhaps they thought it's funny. Or they added the feature to turn off the filter later and had no better idea than to use the same control line as for the power LED.