10 pin --> 26 pin VGA controller pinout and Card compatibility with American Megatrends Super Voyager VLB-III

Question

I'm trying to test an old PC which controls a ABB Bomem FTIR Spectrometer (DA&). The internal PC for this instrument is an American Megatrends, Inc. Super Voyager VLB-III ISA Motherboard

https://theretroweb.com/motherboard/manual/supervoyageriii-mb-man-5f022c433a760286615469.pdf

I want to connect a monitor, the manual states:

“a special 10-pin header can be connected to the feature connector of a standard VGA Controller card. A signal from this header drives HSYNC, VSYNC, and Enable Video Low during Sleep Mode. If a Green PC monitor is used, the monitor switches to its own low power mode during Sleep Mode.”

So it sounds like it needs a ISA VGA card like https://www.artisantg.com/TestMeasurement/62768-1/Western-Digital-VGA-8-ISA-Card

The manual then states:

"J47 Green PC Monitor Connector Attach a 10-wire 10 to 26-pin flat cable between J47 on the motherboard and the VGA Feature Connector on the VGA adapter card or Graphics Accelerator. J47 is shown below. The VGA cable is pictured below. After the timeout period specified in Power Management Setup expires, the motherboard drives the SYNC ENABLE, HSYNC, and VSYNC signals Low through open collector outputs. Monitors that support the Display Power Management Specification (DPMS) can turn power off after examining this condition, saving power."

I haven't been able to find the pinout or any 10 pin --> 26 pin flat ribbon cables. Does anyone know what the pinout is for those cables? Can anyone tell what VGA controller card would be compatible with this motherboard (8 vs 16 bit? etc).

thanks oman

Answer 1

Page 54 of the motherboard manual gives the pinout of its custom 10-pin connector as follows:

Pin Signal Pin Signal 1 N/C 2 N/C 3 N/C 4 N/C 5 TTL output for SYNC enable 6 Open Collector output for HSYNC control 7 N/C 8 Open Collector output for VSYNC control 9 N/C 10 GND

Details on the VGA Feature connector are hard to find. My copy of Upgrading and Repairing PCs (10th anniversary edition) from 1998 describes it as poorly used, partially because it was poorly documented by IBM in the first place, and doesn't actually give a pinout for it. I have, however, found an archived copy of an email from 1993 online that gives the required details:

component side pin function 1 PD0 (DAC pixel data bit 0) 2 PD1 (DAC pixel data bit 1) 3 PD2 (DAC pixel data bit 2) 4 PD3 (DAC pixel data bit 3) 5 PD4 (DAC pixel data bit 4) 6 PD5 (DAC pixel data bit 5) 7 PD6 (DAC pixel data bit 6) 8 PD7 (DAC pixel data bit 7) 9 DAC clock 10 DAC blanking 11 Ext. horizontal sync 12 Ext. vertical sync 13 Ground

back side pin function 1 Ground 2 Ground 3 Ground 4 Select Internal Video 5 Select Internal Syncs 6 Select Internal DAC 8..11 Ground

A similar pinout for ATI graphics cards in the same email matches the above information.

On that basis, it appears that you need four connecting wires, as follows:

Motherboard VGA Card Pin 5 - TTL sync enable Back pin 5 - Select internal sync Pin 6 - HSYNC output Front pin 11 - External HSYNC Pin 8 - VSYNC output Front pin 12 - External VSYNC Pin 10 - Ground Back pin 1-3 or 8-11 - Ground

Note that this cable allows your motherboard to override the VGA card's sync signals, and thus power off the monitor when the machine is idle. It isn't required for normal functionality of the graphics card.

As such, your machine should support any standard 8-bit or 16-bit ISA graphics card (though you presumably want to stick to VGA, and avoid older EGA/CGA standards unless you have a compatible monitor). The very best cards your board supports would be one that uses the VESA Local Bus (VL-Bus) slots, which were designed to allow fast direct memory access for video cards in the pre-PCI bus days. These will be rarer than regular ISA VGA cards, however.