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View Full Version : What's the most advanced ISA video card to include a VESA feature connector?



DeathAdderSF
May 16th, 2017, 05:37 PM
Hello, all.

To quote the thread title: "What's the most advanced ISA video card to include a VESA feature connector?"
For 8-bit and / or 16-bit -- though 16-bit are the ones I'm most concerned with.

Thanks in advance.

1ST1
May 17th, 2017, 12:17 AM
Probably ATI Mach64 ISA, when you find some in eBay, they are quite expensive. But they have up to 4 MB videoram.

DeathAdderSF
May 17th, 2017, 02:35 AM
I own a Mach64 ISA. It does not have a VESA feature connector.

Xacalite
May 17th, 2017, 06:02 AM
There were various Mach64 ISA cards, some with feature connector, some without.

But if you really want the most advanced stuff, search for coprocessor cards with TIGA chipsets.
Some such cards were coprocessor-only and required separate VGA card, others integrated both VGA and TIGA chipsets.
See eg. Number Nine GXiTC Level 29.

Anonymous Coward
May 17th, 2017, 07:13 AM
What is the "vesa" feature connector? I have mach64 ISA and it appears to have a normal vga feature connector.

lutiana
May 17th, 2017, 07:15 AM
What is the "vesa" feature connector? I have mach64 ISA and it appears to have a normal vga feature connector.

I assume OP means a VL-Bus based card.

eeguru
May 17th, 2017, 09:22 AM
I assume OP means a VL-Bus based card.

That wasn't what I assumed. It's hard to go from feature connector - which is a real thing - to VESA local bus.

lutiana
May 17th, 2017, 09:35 AM
That wasn't what I assumed. It's hard to go from feature connector - which is a real thing - to VESA local bus.

Hmm, well I could be wrong then, I can see how that assumption could fit too.

Xacalite
May 17th, 2017, 10:23 AM
It has nothing to do with VESA Local Bus.
There were at least four standards for feature connectors:
* EGA Feature Connector - 32-pin
* VGA Feature Connector - 26-pin edge connector
* VESA Feature Connector - 26-pin, but NOT edge? This is what I saw on many cards...
* VESA Advanced Feature Connector - 80-pin

DeathAdderSF
May 17th, 2017, 10:54 AM
What is the "vesa" feature connector?

This connector, found at the top of cards...

38612

Pardon the confusion.

lutiana
May 17th, 2017, 11:07 AM
I did ask this on another thread, but did not get an answer that made sense to me, but I'll ask again here. What is the purpose of these connectors? And why, like they said in the other thread, would you want to add an external clock signal to an EGA (and presumably a VGA) card?

bear
May 17th, 2017, 11:35 AM
The VGA feature connector is different from the EGA one. For VGA it provides pixel DAC / sync signal output to an option card.

Typically, this was put to use in one of two ways:

1. For high-resolution display adapters in the days before combined VGA chipsets, to allow a single monitor solution without requiring the high-resolution display to implement its own VGA-compatible function. The high-res adapter would "pass through" the signal from the VGA card for low-res modes, switching to its own signal for high-res modes.

2. For motion-video type adapters, to overlay motion video on top of some region of a VGA display, using a chroma key type arrangement. The VGA signal would be passed through, with some displayed region of solid (perhaps configurable) key color replaced by the output of the motion-video adapter.

Doing it this way was typically cleaner and more reliable than using the external video connector for the same job, as you got digital pixel data, rather than the analog (post-DAC) signal that would be sent to the monitor.

This is the VGA feature connector, though, and not the VESA Advanced Feature Connector (which allows for more video bandwidth - something you'd need if you were expecting to pass through much more than 800x600, or more than 8 bits of pixel depth). The VESA Advanced Feature Connector is an 80-pin arrangement that looks like a SCSI SCA connector. IME it wasn't widely implemented; I've only ever seen one on the Compaq QVision 2000.

I don't understand what "most advanced" could possibly mean in specific enough terms to answer the OP's question.

vwestlife
May 17th, 2017, 11:38 AM
I did ask this on another thread, but did not get an answer that made sense to me, but I'll ask again here. What is the purpose of these connectors?
For TV tuner, DVD/MPEG decoder, and specialized animation cards to have their output overlayed onto the computer's normal video output. This is back when CPUs were too slow to handle all of this fancy schmancy graphics processing in software, so they used dedicated hardware to do it, just like the 32X add-on for the Sega Genesis/Mega Drive.

DeathAdderSF
May 17th, 2017, 11:39 AM
I don't understand what "most advanced" could possibly mean in specific enough terms to answer the OP's question.

Most impressive technical specs.

Xacalite
May 17th, 2017, 12:14 PM
https://www.youtube.com/watch?v=U9HkUA9REHc
For ISA, you can't find a card noticeably better than this.
4 MB RAM for TIGA coprocessor, allowing 1024x768x24bpp or 1280x1024x16bpp
There's also some separate RAM for Acumos AVGA2 chipset, probably 256 or 512 KB

bear
May 17th, 2017, 02:24 PM
"Most impressive technical specs" is still essentially meaningless.

There's the card Xacalite shared the video for. Then there's the SuperMac Spectrum/24. That was available for ISA bus, used the VGA feature connector, supported 1152x864 resolution at 24 bits and was faster at it than anything else for a while... but no TIGA and only 3 MB VRAM, not to mention drivers only for Windows 3.1. The later ATI Mach 32 on ISA was faster overall but couldn't manage as many pixels at that depth. The Hercules Superstation 3D: ISA bus, TIGA, plus i860, maximum 1280x1024 resolution, but only 2 MB VRAM so tops out in 24-bit mode at 768x576 (presumably because no support for packed-pixel mode).

In the day, the typical tradeoff was, do you want performance for AutoCAD? Or do you want performance for Windows. For a long time you couldn't have both. And the architectures of the various available adapters reflected this.

Unknown_K
May 17th, 2017, 03:37 PM
The Supermac card was EISA I think (have one).

bear
May 17th, 2017, 03:44 PM
Yes, it was also available for EISA and VLB.

DeathAdderSF
May 17th, 2017, 09:55 PM
Thanks for the info. Now the question is: do any of you here have one of these nice cards for sale? ;)
In the mean time I'll keep an eye out on eBay and such...

gslick
May 17th, 2017, 10:18 PM
The VGA feature connector is different from the EGA one. For VGA it provides pixel DAC / sync signal output to an option card.

Typically, this was put to use in one of two ways:

1. For high-resolution display adapters in the days before combined VGA chipsets, to allow a single monitor solution without requiring the high-resolution display to implement its own VGA-compatible function. The high-res adapter would "pass through" the signal from the VGA card for low-res modes, switching to its own signal for high-res modes.


That is how I first saw it used around the late 1980s or early 1990s as some cards that were enhanced 8514 clones didn't have their own base VGA functionality and needed to be chained to a VGA card to pass that through to a single monitor. If I remember right some of the Compaq Deskpros we used at the time had VGA on the motherboard and provided a riser board that could be plugged into the motherboard to provide the feature connector at the standard height.

Anonymous Coward
May 17th, 2017, 11:40 PM
I don't know how common the Spectrum/24 is, but TIGA cards were fairly cheap and common a few years back.

http://www.ebay.com/itm/SPEA-91610195-QA-12A01-BOARD-P41-R12-Vintage-Graphics-ISA-Board-/361322461458?hash=item54207f3912:g:c2cAAOSwLqFV8Ll s

Here's the only one I can find on eBay at the moment, but at least it should give you a pretty good idea about what they look like.

About the Spectrum/24, for some strange reason it only supported 24-bit colour depth...which is a bummer since 1280x1024 would probably work at 16-bit depth with 3MB VRAM. Very strange for a card being sold in 1994. I believe some of the Spectrum/24 cards also had a module that supplied a VGA core. Mine doesn't have it installed, and I have no idea which IC it used or how much DRAM it had.

bear
May 18th, 2017, 10:25 AM
The VGA feature was an option. It is a low-end Cirrus Logic chip, like the 5422, probably 512 KB. I'd have to go look at mine to be sure. It plugs into the feature connector, just like a standard VGA card would.

bear
May 7th, 2018, 02:26 PM
I checked mine. It's a 256k CL-GD5420.

eeguru
May 7th, 2018, 02:50 PM
I'm not a definitive expert, however I dived a bit into the feature connector while doing some research on an RTL clone of VGA. It is my understanding the VGA card will output complete digital video data for non-palettized video modes in much the same way the EGA card did based on:

Pin 1: PD0 - Primary Blue
Pin 2: PD1 - Primary Green
Pin 3: PD2 - Primary Red
Pin 4: PD3 - Primary Intensity
Pin 5: PD4 - Secondary Blue
Pin 6: PD5 - Secondary Green
Pin 7: PD6 - Secondary Red
Pin 8: PD7 - Secondary Intensity

However, for palettized modes, only the 8-bit LUT index value is output. There are not enough pins to carry true 18-bit color data. Thus any card that makes use of the feature connector for VGA modes must snoop on the ISA bus for DAC color value updates. It really was designed with a light pen in mind and not much else. Though I suppose it could be used for a gen-locked overlay board.

The VESA Advanced Feature Connector adds 32-bit video output. Though they are rare.