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Re: Video on the motherboard

To: riscy@pyramid.com
Subject: Re: Video on the motherboard
From: Andreas Busse <andy@piggy.waldorf-gmbh.de>
Date: Sun, 4 Jul 93 18:50:05 GMT
Reply-to: riscy@pyramid.com
Sender: riscy-request@pyramid.com
> The question is whether to put the video on the motherboard or not.
> Many (most?) of the people interested in this board want to make a
> nice fast workstation.  Any good workstation has fast, big colourfull
> video.  The issue here is just how do you get that glossy video
> and how much to pay for it.

I agree. Although the bombs were very small (if not inexistent)
my idea to have no video on board haven't found friends...

> Its true that the video will be the most expensive optional part or
> the board, coming in at about $100.  I offer some alternatives.

Yes, but a mid-class ISA card costs the same.

> First, video on the board:
>       *  1 MB of Video RAM (supports 1024x1024 8-bits per pixel;
>          better resolutions if 1,2 or 4-bits per pixel are used)
>               or
>          2 MB of Video RAM (supports 1280x1024 8-bits per pixel)
>       *  TI 34076 RAMDAC (has pixel multiplexing, 256 out of 2^16 colors).
>       *  NSC 1882 (generates Video sync, and DMA requests.?)

1024x1024 is a bit unusual :-) Better 1024x768. That wastes ~25% of
the VRAM. 1280x1024 wastes ~33% of the 2 Meg required.
Why not 1152x900 ? That would utilize 99% of 1 Meg VRAM.

> If the peripheral controller is a 3730, then special logic would be
> provided to generate the shift register load cycles for the VRAM,
> and, of course the main CPU does the video support.  If the peripheral
> controller is the 3041, then the VRAM may be connected to either
> processor.  If it was connected to the main CPU, the 3041 could still
> access the VRAM anyhow, albeit a little slower.  The 3041 could
> generate the special VRAM cycles.

Generating the shift register load and clocking out that stuff
could be realized by some GALs.

> Advantages of video on the motherboard:
>       *  High bandwidth direct connection to CPU
>       *  Linear memory organization (good for software)
> Disadvantages:
>       *  Adds significant cost to the end price of the motherboard.
> For those that don't want the video section, the motherboard could
> be sold with empty sockets for the whole video section.  A separate
> video add-on package containing the chips to plug in could be put
> together.

This is a good solution. I like it !

> Video on a VESA or local bus connector:
> (I understand that VESA and local bus are the same thing; correct me
>  if I'm wrong.)

Correct me too, please :-)

> Advantages of VESA video:
>       *  High bandwidth direct connection to CPU
>       *  Linear memory organization available
>       *  Cards available to do this already
>       *  No work for us to design video
> Disadvantages of VESA video:
>       *  CPU is assumed to be an x86 (hard work to connect to a R3000)
>       *  VESA is apparently going to die soon.
>       *  VESA and its replacement, PCI, require licenses to use.
>       *  Higher total cost than motherboard solution

The fact that VESA is on the way to die should be enough
reason not do use VESA video cards.

> Video on the ISA bus (assuming there is one):
> Advantages of ISA video:
>       *  Cheapest video solution
>       *  ISA easy to implement
>       *  Accelerator cards available that support reasonable speed
>       *  Almost everyone already has a ISA video card
>       *  Software already exists
>       *  No work for us to design video
>       *  Cards will be around for a while (ISA will not die soon)
> Disadvantages of ISA video:
>       *  Still not as fast as direct connect video, even with accelerators
>       *  Higher total cost than motherboard solution (if using fast card)
>       *  Very complicated interface (VGA)

The greatest disadvantage of ISA video cards is loooow speed for
nearly the same price we would pay for *fast* on-board video.

> No video at all:
> Advantages:
>       *  Cheapest solution of all
> Disadvantages:
>       *  Must have external terminal
>       *  Not as cool!

Hmm. No video at all can't be a solution...

> My personal opinion is that the video should be on the motherboard as
> an option.  That is, the video designed and tested, but motherboards
> shipped with empty sockets.  I'm one of those that want the really cool
> huge colour monitors.

I don't need huge colour monitors. I'm satisfied with a 17" monochrome
display. But I don't mind if it's colour :-)


Andreas Busse             | e-mail: andy@piggy.waldorf-gmbh.de (home)
Eislebenstrasse 5         |         andy@resi.waldorf-gmbh.de (office)
D-5300 Bonn 1             | Phone:  +49 (0)228-252687


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