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#81 |
Registered User
Join Date: Jun 2013
Location: Australia
Posts: 685
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If the left mouse button is BFE101, what is the joystick fire button?
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#82 |
Registered User
Join Date: May 2006
Location: Kilmacolm
Age: 46
Posts: 632
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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. |
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#83 |
Global Moderator
Join Date: Sep 2006
Location: Germany
Age: 46
Posts: 32,587
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It was cheap
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#84 |
Registered User
Join Date: May 2006
Location: Kilmacolm
Age: 46
Posts: 632
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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?
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#85 |
WinUAE developer
Join Date: Aug 2001
Location: Hämeenlinna/Finland
Age: 49
Posts: 26,611
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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. |
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#86 |
Glastonbridge Software
Join Date: Jan 2012
Location: Edinburgh/Scotland
Posts: 2,243
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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.
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#87 | |
Registered User
Join Date: Feb 2008
Location: RNO
Posts: 1,010
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Quote:
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. |
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#88 |
Registered User
Join Date: Sep 2012
Location: Dorathea/AT
Posts: 376
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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).
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#89 |
Registered User
Join Date: Feb 2007
Location: Melbourne, Australia
Age: 41
Posts: 3,773
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#90 |
It's all in the reflexes!
Join Date: Nov 2009
Location: Wingkong warehouses
Posts: 206
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@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 ! ![]() |
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#91 |
It's all in the reflexes!
Join Date: Nov 2009
Location: Wingkong warehouses
Posts: 206
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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. |
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#92 |
Registered User
Join Date: Sep 2012
Location: Dorathea/AT
Posts: 376
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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.
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#93 |
Registered User
Join Date: May 2013
Location: UK
Age: 44
Posts: 351
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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 ![]() |
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#94 | ||
Moderator
Join Date: Aug 2008
Location: Sidcup, England
Posts: 10,300
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Quote:
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#95 | |
Registered User
Join Date: May 2013
Location: UK
Age: 44
Posts: 351
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Quote:
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#96 |
Registered User
Join Date: Apr 2011
Location: birmingham
Age: 55
Posts: 2,827
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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.
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#97 |
Registered User
Join Date: Jun 2013
Location: Australia
Posts: 685
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They might have tested the motherboard with it's RAM on a daughter board
before soldering it on, because RAM is expensive. |
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#98 | |
Local Moderator
Join Date: Oct 2009
Location: Lancashire, UK
Age: 48
Posts: 1,737
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Quote:
Question: why does turning on the audio filter make the power LED go dim? Last edited by lifeschool; 18 June 2013 at 17:10. |
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#99 |
Registered User
Join Date: Jan 2002
Location: Germany
Posts: 7,050
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#100 | |
Registered User
Join Date: Jan 2002
Location: Germany
Posts: 7,050
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Quote:
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. |
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