TV Capture Cards w/ ATI Mach64 (fwd)

Sgt Daniel W. Erskine (
Thu, 19 Oct 1995 14:33:10 -0500 (CDT)

Thought this might help us ATI Mach64 and graphic accelerator users :>

"THERE IS NO SANITY... Just organized CHAOS!!!"

Sgt Daniel W. Erskine ""
COMM: (618) 256-6891 ""
AUTOVON: 576-6891 ""

---------- Forwarded message ----------
Date: 18 Oct 95 16:50:17 EDT
From: ATI Support <>
To: "Sgt Daniel W. Erskine" <>
Subject: TV Capture Cards w/ ATI Mach64

Dear Mr. Erksine,

The 64-bit architecture of ATI mach64 based products, consist of a complete
64-bit internal data path with a high-end RAMDAC and VRAM. This configuration
allows the RAMDAC to read directly from the VRAM to the screen when operating in
accelerator mode.

This architecture makes it possible to deliver high performance, high resolution
high color depth and high refresh rate for todays advanced platforms. The
Display drivers developed for the 64-bit architecture are written to operate in
accelerator mode and to utilize the full capabilities of the architecture.

The VGA Feature Connector intercepts the standard VGA pixel bus that exists
between the graphics controller and the RAMDAC. This is in keeping with the
original VGA feature connector specification.

The mach64 display drivers use the entire 64-bit path that exists between the
RAMDAC and the VRAM, and results in the VGA pixel bus being bypassed. When this
occurs, any device attached to the feature connector (Capture Cards, Overlay
products, etc) will not receive display information. This will cause conditions
of "no display" or "black windows".

This is a multifold issue, and to our knowledge, the limitation of the VGA
feature connector, the 64 bit architecture, accelerated 64-bit Windows Drivers
and VRAM based Memory Configurations will occur with most all 64-bit Graphics

However, the VGA Feature Connector on ATI mach64 VRAM products will operate
satisfactorily in the Windows environment, in VGA Mode, by using the MS supplied
VGA Windows Drivers (Non-Accelerated Drivers).

ATI Technologies apologies for the delay in providing a statement regarding the
VGA Feature Connector usage with ATI mach64 Windows Accelerated drivers.

Customers experiencing difficulties with these features may wish to try:

1) a mach64 DRAM product,


2) M64VBE VGAWONDER compatibility mode, and the MS SVGA drivers.

You can try our VIDEO-IT! capture card. It does not use the mach64 Feature
Connector, but gets the passthough information via the IS/VLB bus.

Should you require any further information or assistance, do not hesitate to
contact us again.

Sincerely yours,

Grant Kimura