IBM SVGA Adapter

IBM SVGA Adapter/A Driver Disk 
@90EE.ADF- SVGA Adapter/A

It is also known as the ISO Display Adapter/A 39G3298

WBST said:
Win3.11 drivers for SVGA Adapter/A: 640x480 @ 256 colors and 800x600 @ 256 colors
Win3.11 drivers for 8525SX and Thinkpad 700C/720C: 640x480 @ 256 colors support

These drivers should support the PS/2 planar video of the 8540SX and the 8557SX as well as long as 512KB video ram is installed and the VESA DOS TSR makes the resolutions (640x480 and 800x600) available to the driver.

Other test results are very appreciated since I could test with the SVGA Adapter/A only. Be careful with original IBM/PS2 tube monitors because a 800x600 resolution may damage them.


IBM SVGA Adapter/A 256c   
SVGA /A Developments 
ADF Section



IBM SVGA Adapter/A
L5, L9, L10 TDK ZJY-2P 
U43-46 Toshiba TC511665BZ-80 
U47 ICS ICS2494M 
U50 AMD 39G6131
U53 INMOS IMSG176J-80Z 
U60 OKI 85F0120 
U61 TI 42G3410 
Y1 F14.3H1
INMOS (a British Company) was acquired in 1989 by  SGS-THOMSON Microelectronics. 

  This puppy has 512K of VRAM. It is supported as a generic SVGA adapter. The SVGA refers only to the 640x480 resolution, NOT color depth. NO specific Win xxx drivers exist. Or for that matter, OS/2 (VGA256).


SVGA /A Developments  

Wolfgang Gehl spake thusly:

While playing with a Solaris setup on a 9595 I ended up creating a DOS partition and giving SVGA Adapter/A a try.
This mysterious card currently has no OS support beside OS/2 with VGA resolution and 256 colors and VESA VBE support for DOS.

First I tried the VESA driver from m95svga.exe. It offers VESA VBE 1.2 support for 256 colors for resolutions up to 800*600 pixels customized for the display's horizontal refresh rate. Since I use a LCD monitor, I disabled 640*400 and the 16 colors interlaced 1024*768 mode and choose 60Hz for 640*480 and 800*600 mode.

Do you remember trying to play "Simcity 2000" or "The Settlers" with XGA/2? Never got it running. With SVGA/A and loaded VESA driver these games are playable without a hitch. It's kind of a crazy to play DOS SVGA games on a 9595 RAID5 Server, however, it works!

Simcity 2k for DOS contains a VESA driver collection with an IBM directory. Inside are two VESA drivers. One is for XGA/XGA2 (for Simcity dysfunctional, LOL) the other one is for the PS/2 25SX planar video. A look at Williamís 25SX site shows that the SVGA/A chipset is sitting on the 25SX planar. And he mentions that it is common on 40SX and 56/57 SX/SLC planars too.

A search for "IBM 84F7985" took me to a thread on a PS/1 forum with the title "The mystery of the PS/1 2121ís (S)VGA"
https://ps1stuff.wordpress.com/2016/09/13/the-mistery-of-the-ps1-2121s-svga/
Obviously IBM used this chip in several x86 machines, and for us most important, inside the micro channel PS/2 ThinkPads too. A ThinkPad without Windows drivers is hard to imagine. And right, Louis has the 256 colors Windows 3.1 driver, which is in fact the 25SX_AND_700C_AND_720C display driver:
http://ps-2.kev009.com/ohlandl/9552/9552_700C.html
Since we have the driver, we have the chipset name too: IBMVGA256c

Well, don't expect to much, the Windows 3.1x setup offers 256 colors for 640x480 pixels only. It works in conjunction with the DOS VESA VBE driver and seems to be an early if not the first Windows VESA VBE driver at all. I've tested with windows 3.1, 3.11, and 95. With 95 the 16bit driver slows down the system and there are severe incompatibilities e.g. with explorer.exe.

Here is the incomplete information I could find so far:

The IBMVGA256c chipset
======================

IBM PS/1 2121 [1]
-------------
Year:            1991 (?)
Video chipset:   IBM 84F7985 (= TI CF62011BPC)   IBMVGA256c
RAM DAC:   INMOS IMSG171P-35 [2]
                             35MHz 8 Bit DAC up to 256 colors from a total of 262,144 colors
RAM:             256KB 100ns VRAM

IBM PS/2 8540SX
---------------
Year:            1991
Video chipset:   IBMVGA256c (?)
RAM DAC:         ?
RAM:             ?

IBM PS/2 8557SX [3]
---------------
Year:            1991
Video chipset:   IBM 84F7985 IBMVGA256c
unknown:         IBM 85F0120
RAM DAC:         INMOS IMSG171P-50 [2]
                 50MHz 8 Bit DAC up to 256 colors from a total of 262,144 colors
RAM:             512KB 80ns VRAM

IBM PS/2 8525SX [4]
---------------
Year:            1991 (?)
Video chipset:   IBM 84F7985 IBMVGA256c
RAM DAC:         INMOS IMSG171P [2]
                 (?)MHz 8 Bit DAC up to 256 colors from a total of 262,144 colors
RAM:             512KB 80ns VRAM

IBM PS/2 Thinkpad 700C/720C [5]
---------------------------
Year:            1992
Video chipset:   IBM 39G8600 IBMVGA256c
Clock chip:      ICS ICS2494 [6]
                 135MHz Dual Video/Memory Clock Generator for VGA, Super VGA, XGA
                  video adapters, 8514A, TMS34010, TMS34020
RAM DAC:         ?MHz on chip?
RAM:             512KB 80ns VRAM

IBM SVGA Adapter/A [7]
------------------
Year:            1992 (together with Server 85)
Video chipset:   IBM 42G3410 (= TI CF63011PCM) IBMVGA256c
unknown:         IBM 85F0120 (= OKI M7U016-008)
Clock chip:      ICS ICS2494 [6]
                 135MHz Dual Video/Memory Clock Generator for VGA, Super VGA, XGA
                 video adapters, 8514A, TMS34010, TMS34020
RAM DAC:         INMOS IMSG176J-80Z [8]
                 80MHz 8 Bit DAC up to 256 colors from a total of 262,144 colors
RAM:             512KB 80ns VRAM

Driver Support
--------------
DOS:   generic: 700c120-exe [9]
            SVGA/A:  m95svga.exe [10]

            VESA/VBE driver*

            256KB VRAM, at least 40MHz RAM DAC 800x600 pixels, 16 colors, 60Hz**
            512KB VRAM, at least 30MHz RAM DAC 640x480 pixels, 256 colors, 60Hz
            512KB VRAM, at least 40MHz RAM DAC 800x600 pixels, 265 colors, 60Hz**
            512KB VRAM, at least 50MHz RAM DAC 1024x768 pixels, 16 colors, 43Hz I***
            256KB VRAM, at least 30MHz RAM DAC 132-column x 25-row text

 * RAM DAC requirements are calculated with the formula
                 line frequency in kHz = ([vertical resolution] * [horizontal refresh rate] Hz + [vertical resolution] * [horizontal refresh rate] Hz * 0,1)/1000
                 RAM DAC pixel frequency in MHz = ([horizontal resolution] * [line frequency] kHz + [horizontal resolution] * [line frequency] kHz *0,2)/1000

 ** the IBMVGA256c chipset does 800x600 pixels, 56Hz too but LCDs usually don't support refresh rates below 60Hz and you will not accept a 56Hz refresh rate on aCRT monitor.

*** LCDs usually don't support an interlaced video resolution. 1024x768 pixels,16 colors, 60Hz requires at least a 70MHz RAM DAC


OS/2:       from v2.11 up build in under the name "IBM VGA 256c"
            640x480 pixels, 256 colors with 512KB VRAM, at least a 30MHz RAM DAC[11]

Windows 3.1x:    generic: 700c120-exe [9]
            640x480 pixels, 256 colors w/ 512KB VRAM, at least a 30MHz RAM DAC together with DOS VESA/VBE software driver

[1] https://ps1stuff.wordpress.com/2016/09/13/the-mistery-of-the-ps1-2121s-svga/
[2] IMSG171P is compatible to BT476:
https://www.datasheetarchive.com/pdf/download.php?id=527994991358bc5dc0a9e619b66f0a2d71ba0d&type=O&term=IMSG171
    BT47x circuit description:
https://www.datasheetarchive.com/pdf/download.php?id=dd6f6622ae7025772fc684bf7840a63ab87fae&type=M&term=bt476
[3] http://ps-2.kev009.com/ohlandl/8557/8557SX-Planar.html
[4] http://www.walshcomptech.com/ps2/25sx.htm
[5] http://www.vgamuseum.info/images/vlask/ibm/39g8600f.jpg
    http://www.vgamuseum.info/images/vlask/ibm/39g8600fz.jpg
[6] ftp://bitsavers.informatik.uni-stuttgart.de/pdf/integratedCircuitSystems/1994_Integrated_Circuit_Systems_Data_Book.pdf, pp. 161-165
[7] http://www.vgamuseum.info/images/palcal/ibm/44_ibm_fru_71f4877_top_hq.jpg
[8] https://www.datasheetarchive.com/pdf/download.php?id=30c4f464de799e8bfcadd50feda3f34ef84d46&type=M&term=IMSG17
[9] http://ps-2.kev009.com/ohlandl/9552/r700c120.exe
[10] http://ps-2.kev009.com/ohlandl/video/m95svga.exe
[11] a higher resolution may be possible according to:
http://www.edm2.com/index.php/DDDR/2_-_32-Bit_Super_VGA_Display_Driver




AdapterId 90EE SVGA Adapter/A

FixedResources io 3b0h-3bbh 3c0h-3dfh  int 9

Video I/O Address
   I/O address range for display controller registers.  Each adapter must have a unique address range. 
        <"Instance 6: 2160h - 216Fh">, 1: 2110-211F, 2: 2120-212F, 3: 2130-213F, 4: 2140-214F, 5: 2150-215F, 7: 2170-217F, 0: 2100-210F
 
 

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