Cornerstone ImageAccel

@80A5.ADF High Resolution Display
@80A5.ADF DualPage Display (similar, rename to @80A5.ADF)
@80A6.ADF ImageAccel Display

Unofficial Cornerstone ImageAccel site (by Ulrich Trunk, archived)

ImageAccel MC161i
ImageAccel MC164
ImageAccel MC1608C/11
Cornerstone Monitors
ADF Sections (80A6)


ImageAccel 1
Win95 and Win3.1x
Win NT 4.0
Win NT 3.51
OS/2 Warp 3.0 and 2.1x

CVC (Whazzat?)
MCA Windows 3.x (Not available)

MC164 (thanks, Brad!)

Don't expect too much, the W95 drivers were just warmed over W3.XX and caused my model 95 to run in DOS mode. Maybe the NT drivers are better, I don't know as I have never tried them. The W95 drivers do support the 6091-19 as a menu option, which is kind of nice. LINK (DEAD)

ImageAccel MC161i

JP1 Monitor Selection
JP30,71 Solder pads
L80 LED (for what?)
P2 DB15 port
U1 50.000 MHz osc
U2 Cornerstone 1212288-200
U12 Motorola 7905CT
U32 MC161i BIOS
U40 Cypress CY7C128A-15VC
U43,44 BI 8A330
U50-55 Solder pads for VRAM
U56,57 TC524256BZ-10
U70 Unknown (under heatsink)
U72,73 Motorola 10H116
U110 CTI 2012371-100
U150-153 Empty
X110 EC2-143 xtal

ImageAccel MC164

1A-1H NEC D42273V-10
3J 131.00 MHz
4J ?
5A L1A4678
8A L1A4220
10J Altera EPB2001LC
11A 438-04ME
13E,13F Motorola 10H116
VR1 Motorola 7905.2CT

This card has 8 NEC D42273V-10 VRAM chips.

ImageAccel MC1608C/11 [P]

JP1 monitor type selection
JP12 jumper solder pads
JP30 jumper solder pads (shorted)
LED Green LED (?)
P90 15 pin VGA connector
TP1 MC1608C/11 12660-003 (BIOS)
U1 50 MHz osc
U2 Cornerstone 1212288-200
U50-53,80-83 TC528257J-80
U140 BT471KPJ80 RAMDAC (base video)
U111 ICS1562AM PLL (pixel clock)
U151,152,155,156 socket artifacts

Monitor Support

The MC1608C/11 is a 2 MB graphics card capable of driving fixed frequency monitors. It is no surprise that the Cornerstone monitors of the time (1993/4) are supported, but – pretty surprisingly – also the whole of the 6091 series by IBM. Specifically:

  • Cornerstone: Color 21/80, Color 21/75, Color 20/72, Color 20/70, Color 21, Color 21/76, Color 17, Color 19, DualPage 120 Color
  • IBM: IBM 6091-16, 19, 21, IBM 9521/9527 (supported by the C/11 and C/12 only)

Selecting the monitor is done via a set of jumpers in the JP1 position of the card (top right corner).

JP1 Settings

Display Type JP1 Position
1 2 3 4
Autosync on on on on
Cornerstone Color 19 (1) off on off on
IBM 6091-16 and -19i on on off on
IBM 6091-19 on off on on
IBM 6091-23 on off off on
Cornerstone Color 20/70 (2) off off on on
Cornerstone Color 21/76 (3) off on on on

(1) Not supported for ImageAccel 1280 controller
(2) ImageAccel 1600/70 and 1600/76 controllers only
(3) ImageAccel 1600/76 controller only

More info about setup under NT 4.0 at Ulrich Trunk's Unofficial ImageAccel site.


The card only supports non-interlaced display modes. The minimum horizontal rate required for multi-frequency displays is 64 kHz!

The card is capable of 1600x1280 @ 76 Hz refresh (~120 kHz horizontal rate, ~211 MHz pixel clock), so be EXTREMELY careful or you will fry your monitor. Supported resolutions:


Lower resolutions (down to 400x300) are provided by the drivers zoom feature (6 levels, up to 4x). Color depth is always 8bpp (256 colors out of 16.7M).

Cornerstone Monitors

CS Fixed Frequency Color Monitors with ImageAccel Video Controllers.
Monitor - Color 21/76, Color 20/70, Color 19

The Color 21/76, Color 20/70 and Color 19) are fixed frequency color monitors. These monitors are not compatible with standard VGA video controllers. Standard VGA video cards require a monitor that operates at 31.5 kHz horizontal scan frequency with a 60Hz vertical refresh rate. These monitors have only been tested using the following ImageAccel video controllers.

Color 21/76  ImageAccel 1 - MC 1608C/11
Color 20/70  ImageAccel 1 - MC 1608C/11, 1608C/12
Color 19     ImageAccel 1 - MC 1608C/10, 1608C/11, 1608C/12

Experience (by Ulrich Trunk)


MC1608C/11 (JP1-1..4 shorted) in PS/2 Server85 (9585-0XT, 486 DX/2 66MHz), XGA, XGA-2 or SVGA/A base video, ESCOM 78 kHz autosync monitor (DEC clone) connected to MC1608C, self made terminator plug for base video (75Ohms 1-7, 2-8, 3-9, short 10-11).


All XGA 16bpp modes don't work (Limitation of BT471 RAMDAC or MCA AVE?)
Base video refresh rates can be changed without a problem (XVGARATE works).
Video modes available on XGA base video (obviously) depend on monitor ID delivered by terminator plug. SVGA/A and XGA-2 don't require the terminator plug at all.


DOS 6.22: Drivers for 1280 X 1024 @ 64HZ refresh work OK
   Black screen with drivers for 1600 X 1200 @ 64Hz refresh

WfW 3.11: Drivers for 1280 X 1024 @ 64HZ refresh work OK
   Black screen with drivers for 1600 X 1200 @ 64Hz refresh

OS/2 2.11, 3.0, 4.0: Drivers for 1280 X 1024 @ 64HZ refresh work OK
   Drivers for 1600 X 1200 @ 64Hz refresh not yet tested

Black screen: No whispering "can't sync" sounds from my monitor. Can exit windows back to the DOS prompt via shortcuts. Same for IA DOS driver test screen. 64Hz @ 1600 X 1200 equals 78.1 kHz. This is the slowest refresh for this mode the drivers offer, but 100Hz beyond the limit of my monitor. Will try a faster monitor soon.

I Used the cable that came with my monitor. Does the MC1608C card read out some sort of monitor ID like the XGA, XGA-2 and SVGA/A cards? One of the driver READ.MEs mentions a special 15pin VGA - 5 BNC cable that came with the card, but which I don't have. Any clues?

AdapterId 80A6 ImageAccel Display

Primary or Secondary Video Adapter
   Choose primary if ImageAccel is the primary display, otherwise choose secondary if VGA is the primary display. (Note: If you select the standard of <Primary> for the video adapter, you’ll see all DOS based messages on the monitor attached to the ImageAccel. <Secondary> means that you use the ImageAccel only for HiRes output (which would require another monitor attached permanently to the BVA).
    <"Primary">, Secondary

I/O base address
   Choose a 2 byte I/O block with no conflicts
    <"2000" (2000-2001)>, 2010 (2010-2011), 4000 (4000-4001), 4010 (4010-4011)

Memory base segment address
   Choose a 8K memory block with no conflicts.
    <"0DE000" (DE00-DFFF)>, 0DC000 (DC00-DDFF), 0DA000 (DA00-DBFF), 0D0000 (D000-D1FF), 0CE000 (CE00-CFFF), 0CC000 (CC00-CDFF), 0CA000 (CA00-CBFF), 0C0000 (C000-C1FF)

Interrupt Selection
   Choose an interrupt with no conflicts.
     <"IRQ 10">, 11, 5, 3

The settings are not critical as long as they don’t conflict with other settings.

Content created and/or collected by:
Louis F. Ohland, Peter H. Wendt, David L. Beem, William R. Walsh, Tatsuo Sunagawa, Tomáš Slavotínek, Jim Shorney, Tim N. Clarke, Kevin Bowling, and many others.

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