Subject: Re: Cybervision
To: None <>
From: Stephen Champion <>
List: amiga
Date: 03/24/1996 16:05:10
	I hate disinformation.  BTW. 2 things - one, in case ya'll haven't
bothered to read, is supposed to be defunct.  I'm writing
to it merely because you did, and I'm not sure if amiga gets forwarded to
	Two, This isn't really the place to discuss general Amiga stuff.
I'm violating this myself only to correct an incomplete and misleading
post.  Try redirectiong anything else on this subject to either 
comp.sys.amiga.* or /dev/null (or NIL:, as the case might be).

Patryk Logiewa said:
> YU SONG wrote:
> > 
> > I am very curiuos. Since every Amiga comes default with some kind of
> > chip memory for graphic and sound data. If I add a graphic card, what
> > will these default chip ram go? Because the graphic data is now handled
> > by add-on graphic card, does that mean chip ram is now shared by sound
> > and processor which increases available mem for processor? Can processor
> > still utilize mem on add-on graphic card while it runs out of mem?
> The Amiga's ChipRAM is one of the Amiga's unique features. It's a memory 
> that is normally used for storing display or sound data where the 
> Amiga's custom chips can access it. Although if You don't have any other 
> (fast) memory, It still can be used by the processor (CPU) as well if it 
> rans out of "normal" FastRAM. But be warned! There is no point adding a 
> gfx card without having FastRAM. In that case You would end up with a 
> much slower display than without the card. With 2megs of RAM on the 
> board You can work with 800x600 resolution in 24bit (16.7mio colours). 
> It depends on Your display what resolution will You be using. Having 14" 
> display ther is no common sense to switch to any higher resolution than 
> 640x480 (512). In that case a lot of the board's RAM will never be used. 
> There are some patches that allow the CPU to utilize the gfx board's 
> memory but I've heard only about patches for Retina card. Still I'd 
> rather recommend adding a REAL FastRAM and forgetting about the hacks of 
> that kind.

	OK - the deal with CHIP on a Amiga with a GFX board.

	Basically - the Amiga's custom chipset uses CHIP memory for fun stuff
like graphics, sound, and a couple of buffers.  AmigaDOS (but not NetBSD) also
uses it for FAST RAM spillover.  Now here's the real bummer under AmigaDOS:

	AmigaDOS has special routines for allocating memory for data that
will be used by the custom chips - these routines will get CHIP or fail.
So, even when you have a graphics board, under AmigaDOS, software that wasn't
written specifically to take advantage of the fact the GFX board can access
FAST RAM will still require the use of CHIP.  I believe that things like
Cybervision and that wierd software the Spectrum came with take care of this
when software is written for their libraries, but I'm not sure - I've only
got an old Retina Z2 with the dead minimal RetinaEMU software, and have never 
used any of the other RTG software.
	End result - often your chip memory will still be eaten up by software
not designed to take advantage of the board and the software controlling it.
This really sucks, as a 800x600x24 and 1280x1024x8, and other such higher-than-
native-amiga-modes will make that 2M CHIP disappear pretty fast.
	And, of course, CHIP is still used by anything requiring access to the
native sound hardware in the chipset or the chipset's other functions (serial
falls into this category, I believe).

	Patryk is right in that having a GFX board is useless without a decent
bit of FAST memory though - of course, you can't even boot NetBSD without
some FAST, so I assume that's not a worry.  I'd say you should put yourself
up to 8Mb FAST before investing in a GFX board.  I still run out occasionally
with 8, but can do most of what I want to.  
	I have a slightly different problem myself - since RetinaEMU doesn't 
have any facilities for using FAST instead of CHIP for GFX data, I tend to run 
out of CHIP first - with better RTG software this shouldn't be as much of a 
problem, but will consume more FAST memory.

	Under NetBSD, however, CHIP memory, FAST memory, and the memory on a
graphics board are all held separate.  Your FAST memory is your primary
memory, anything needing the custom chips is bounced into CHIP by the kernel
drivers, and your GFX board memory is used only for the current display (what's
on screen at the moment).

	Now what really eats me about what patryck is saying is the bit about 
there being no sense in going beyond 640x400 on a 14" display.  In the bad old
days before I got my current monitor, I was quite happy with 1024x768 with
my crappy old 14", and made very frequent use of 800x600 (to conserve CHIP 
mem with RetinaEMU).  I now have a really sweet little 15" monitor that'll
crank it up to 1280x1024 before becoming interlaced, I also barely run AmigaDOS
these days, so conserving CHIP memory isn't a worry - I normally run X at
1152x900x8 and am quite happy with it (well, the Retina Z2 is slow as a dog,
but everything is slow as a dog an on '030-25, so I'm pretty much used to it).

	There's no real need to waste the extra 400 bucks(US) on a spiffy
17" monitor - a _good_ 15" monitor will do the job, and if you can stand for
1024x768, even a 14" will do.  Of course, if spending the money isn't really a 
problem, or you are easily susceptible to eye strain, then go for the 17".

> > Does graphic add-on card with 2 mega enough for normal usage? I usually
> > sue some business software, not a video or graphic professional, even
> > semi. is 2 mega enough for X11R6 on NetBSD-Amiga? Price of 4 mega card
> > is really steep.
> As I've written before it mainly depends not on the kind of work You do, 
> but on the kind of display you attach to it. And the kind of display 
> should be chosen with the work in mind. If You don't do proffesional 
> graphics, The 17" multiscan should be pretty enough on one side and 
> wouldn't waste too much of the board's potential on the other.

	A 17" will cost an arm and a leg - if you buy anything bigger, don't 
expect to have any body parts left to use it.  With good eyesight and good 15",
you should be able to handle up to 1280x1024.  The extra money is better spent 
on more memory, CPU, and disk.
	Addmittedly, you really should try it before you buy - there are some
people who think it strains the eyes at first, but most will get used to it.
People have been conditioned to low resolutions by cheapskate manufacturers.

	Oh - One thing about the graphics boards is that the memory on
the board is only used for what is currently being displayed (unlike CHIP
memory in the normal Amiga configuration), so you only have to have the 
memory for what's on screen.  2Mb will give 800x600x24, 1024x768x15, and
1280x1024x8, if I remember correctly (and the memory on the board is fast

	While many people here are probably using 800x600x24, IMHO, with X,
resolution is far more important that color depth - Xfun starts at 1024x768,
and, unless you want some more shading in Tracy's breasts, you'll find that
8 bit is enough color depth for most purposes.  rxvt isn't exactly a color 
	Being stuck with XamigaRetina, I've not looked at Xamiga24 in quite
a while, but I'm pretty sure it supports 16 bit modes, and possibly 8 bit modes
as well, so you should be able to get at least 1024x768x16 out of it, which is
good enough when you can't get modes with higher resolution.

	One last thing - my definition of a good 15" monitor:
.28 dot pitch
1280x1024 maximum non-interlaced resolution, at at least 60Hz refresh
digital controls (not necessarily onscreen)

	I'm quite happy with my Amdek AM/815E - picked it up 2 years ago for
$350 - so you can probably find one at a better price now.  The only drawback
to it (or any decent SVGA monitor) is that it doesn't sync down to some of the 
Amiga's native modes (namely the 15Khz to 29kHz horizontal scan rate modes) -
mine goes from 31kHz to 90Khz horizontal.  
	The A3000's display enhancer offsets this problem by bringing most 
modes up into the horizontal scan range of the monitor.  You'll lose a few,
but you won't miss them with a good graphics card.

	Of course, the vast majority of this information, starting with patyck's
response, assumes that you don't already have a decent monitor.  I hope that
I've at least made the issues of CHIP ram with a GFX card a bit clearer.

Stephen Champion                 Workstation and Network Consultant                Onshore, Inc.