Re: VRAM - a lecture by Mark Benson

[the pickle]

At 06:00 +0100 on 27/05/02, Mark Benson wrote:

>>  > From: the pickle <[EMAIL PROTECTED]>
>>>
>>>  At 21:37 -0500 on 26/05/02, Bill Judson wrote:
>>>
  I wonder why Apple decided to cut the bottom off for PPCs at 8 bits? To
  simplify the OS?
>>>
>>>  Actually, that started with the PCI Power Macs.
>>
>>My Performa 6400 (a PCI Power Mac) was quite happy to do 2 and 4 bit video.
>
>I'm wondering then if this is reliant on the System version. The only
>PowerMacs currently in my possession are currently running 9.1 and
>10.1, neither of which support 16 colours. I think 8.1 doeas on my
>840av but is that the OS or the machine?

Here's a guess - it's a relic of the 630 board that those are based on.

The PCI PPCs that were designed from the ground up definitely do *not*
support anything below 8-bit on *any* OS version.

the pickle

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Re: VRAM - a lecture by Mark Benson

[Scott Holder]

At 06:00 AM 5/27/2002 +0100, you wrote:
>I'm wondering then if this is reliant on the System version. The only
>PowerMacs currently in my possession are currently running 9.1 and
>10.1, neither of which support 16 colours. I think 8.1 doeas on my
>840av but is that the OS or the machine?

May well be some of both. I seem to remember when I got my first Mac, an 
LCIII, it was running 7.1 and had the option of 640x400. Later on I upped 
it to 7.5.5 and lost that option. Now, this was when I was a Mac newbie so 
I may have done something else...

Likewise when I got my 6500 more recently, it came with 7.5.5 and did have 
the 16 color option, but now at 8.6 it doesn't...

Scott Holder



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Re: VRAM - a lecture by Mark Benson

[Mark Benson]

>  > From: the pickle <[EMAIL PROTECTED]>
>>
>>  At 21:37 -0500 on 26/05/02, Bill Judson wrote:
>>
>>>  I wonder why Apple decided to cut the bottom off for PPCs at 8 bits? To
>>>  simplify the OS?
>>
>>  Actually, that started with the PCI Power Macs.
>
>My Performa 6400 (a PCI Power Mac) was quite happy to do 2 and 4 bit video.

I'm wondering then if this is reliant on the System version. The only 
PowerMacs currently in my possession are currently running 9.1 and 
10.1, neither of which support 16 colours. I think 8.1 doeas on my 
840av but is that the OS or the machine?
-- 

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Re: VRAM - a lecture by Mark Benson

[John Teffer]

> From: the pickle <[EMAIL PROTECTED]>
>
> At 21:37 -0500 on 26/05/02, Bill Judson wrote:
> 
>> I wonder why Apple decided to cut the bottom off for PPCs at 8 bits? To
>> simplify the OS?
> 
> Actually, that started with the PCI Power Macs.

My Performa 6400 (a PCI Power Mac) was quite happy to do 2 and 4 bit video.


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Re: VRAM - a lecture by Mark Benson

[the pickle]

At 21:37 -0500 on 26/05/02, Bill Judson wrote:

>I wonder why Apple decided to cut the bottom off for PPCs at 8 bits? To
>simplify the OS?

Actually, that started with the PCI Power Macs.

the pickle

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Re: VRAM - a lecture by Mark Benson

[Bill Judson]

Actually the PowerPCs (& Quadras) with 1 MB VRAM can indeed do 1152x870 at 8
bits; it's 1280x1024 that you get only when you up it to 2 (on the
PowerPPCs) -- according to AppleSpec. Of course, they've been wrong
before

But your excellent summary of the mathematics of resolution & bit-depth
would seem to explain why: Power Mac internal video can't do 4-bit depth or
less, & you need 2 megs (when they come in 1-meg units) to achieve the
buffer for 8-bit pixels (1,280k). 

I suggested bandwidth lack (moving the pixels fast enough) because that is
the explaination given me for why these same PPCs can't do 1152x870 at
24-bit (even when they have the VRAM to hold all the pixels), & also (to get
back on topic, or at least on the right list) why the Quadra/LC/Performa 630
& the machines modeled after it can't do 16-bit at 832x624, even though they
have 1 meg of (in this case) DRAM specially dedicated to video.

I wonder why Apple decided to cut the bottom off for PPCs at 8 bits? To
simplify the OS?

~~
On Sun, 26 May 2002 09:23:22 +0100
Mark Benson <[EMAIL PROTECTED]> wrote:

> 
>>While this is true of Quadra built-in video, which tops out at 1152x870
>>(except for the 630 & the like, which top out at 832x624), I was recently
>>looking at AppleSpec, & they say that some early PCI PowerMacs (namely the
>>4400, 7/8200) that can have as little as 1 meg of VRAM can't do 1280x1024,
>>but those upgraded to 2 or more can.
>>
>>Not sure why. Maybe something to do with bandwidth?
> 
> The Video picture displayed on the screen is made of pixels. In order 
> to display these the graphics processor (GPU) requires enough RAM to 
> remember every colour value and what order to put them on screen 
> (i.e. vertical size, horizontal size, bit depth, etc.)
[...] Anyhow, the fact a 1MB PowerMac can't 
> do 1152x870 is that the VRAM is not big enough to remember all the 
> pixels and their locations on screen and other stuff.
> 
> So there you go. That's how it works folks :).
> -- 
> 
> --
> Mark Benson
> 
[...]

-- 
Over,

Jutso

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Re: Performa 476 Netscape problem

[Dean Arthur]

I upgraded mny first '040 Mac [LC-475] with a full 68040-25 cpu from
http://www.sur-tech.com for 19.95 and a 1 GB HD for 25.00. Expanded
video ram to 1 MB fto usde with H-P 17" 1024 x 768 monitor. Expanded ram
from 4 MB on board to 36 MB with 32 MB SIMM for 28.00. Using Netscape
3.04 on it; then on Quadra 650 and now on Power Mac 5400 All-In-One.
Netscape site has download sites for the older versions.

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Re: instant messaging

[Dean Arthur]

I've used Netscape 3.04 on my LC-475 and Quadra 650. Messaging [now or
later] is part of the program and worked G-R-E-A-T!!

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VRAM - a lecture by Mark Benson

[Mark Benson]

>While this is true of Quadra built-in video, which tops out at 1152x870
>(except for the 630 & the like, which top out at 832x624), I was recently
>looking at AppleSpec, & they say that some early PCI PowerMacs (namely the
>4400, 7/8200) that can have as little as 1 meg of VRAM can't do 1280x1024,
>but those upgraded to 2 or more can.
>
>Not sure why. Maybe something to do with bandwidth?

The Video picture displayed on the screen is made of pixels. In order 
to display these the graphics processor (GPU) requires enough RAM to 
remember every colour value and what order to put them on screen 
(i.e. vertical size, horizontal size, bit depth, etc.) On a screen 
with 1-bit (eg. SE/30) screen graphics at 512x384 size, requires 
196,608 bits of memory, one bit for each pixel, which is 24k. The 
same size screen at 8-bit colour (say a Macintosh LC) requires 8 
times that amount of RAM, 192K. That accounts for colour depth 
related to RAM.
Take our screen of 1-bit 512x384 graphics and times both dimensions 
by 2 and you get 1024x768. as each side doubles the screen size 
increases by a factor of 4x the pixels, so 1024x768 at 1-bit requires 
4 times as much RAM, 96k.

Now take a video card with 1MB vRAM.  Because the video card does not 
allot all RAM for the screen matrix, it has to remember the other 
stuff too,it can not physically remember an 1152x870 at 8-bit as it 
requires 979k and is too big for the allotted size of memory space. 
Apple also abandoned 1-bit and 4-bit colour depth successively so 
most PowerMacs do a minimum of 8-bit colour as it was all that was 
acceptable (most later programs and games required it). You'll be 
delighted to know Apple are trying to do away with 8-bit in OS X but 
it is still available in 10.1. Anyhow, the fact a 1MB PowerMac can't 
do 1152x870 is that the VRAM is not big enough to remember all the 
pixels and their locations on screen and other stuff.

So there you go. That's how it works folks :).
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