|
SVGA Developments
SVGA Variants
Driver Support
Information collected by Wolfgang Gehl. Edited by Major Tom.
SVGA Developments
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
800x600 pixels customized for the display's horizontal
refresh rate. Since I use a LCD monitor, I disabled
640x400 and the 16 colors interlaced 1024x768 mode and
choose 60 Hz for 640x480 and 800x600 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) the other one is
for the PS/2 25SX planar video. A look at William’s 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 mistery of the PS/1 2121’s (S)VGA.
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: 9552 700C
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
16-bit driver slows down the system and there are severe
incompatibilities e.g. with explorer.exe.
Below is the (incomplete) information I could find so far.
SVGA Variants
IBM PS/1 2121 (link)
| Year | 1991 (?) |
| Video Chip | IBM 84F7985 (= TI CF62011BPC) IBMVGA256c |
| RAMDAC | INMOS IMSG171P-35
35 MHz 8-bit DAC up to 256 colors from a total of 262,144 colors |
| RAM | 256 KB 100 ns VRAM |
IBM PS/1 Pro 2123
| Year | 1991 (?) |
| Video Chip | IBM 84F7985 IBMVGA256c |
| RAMDAC | INMOS IMSG171P-50
50 MHz 8-bit DAC up to 256 colors from a total of 262,144 colors |
| RAM | 256 KB 80 ns VRAM |
IBM PS/2 8535SX and 8540SX
| Year | 1991 |
| Video Chip | IBM 84F7985 IBMVGA256c |
| RAMDAC | INMOS IMSG171P-50
50 MHz 8-bit DAC up to 256 colors from a total of 262,144 colors |
| RAM | 256 KB 80 ns VRAM |
IBM PS/2 8557SX (link)
| Year | 1991 |
| Video Chip | IBM 84F7985 IBMVGA256c |
| unknown | IBM 85F0120 |
| RAMDAC | INMOS IMSG171P-50
50 MHz 8-bit DAC up to 256 colors from a total of 262,144 colors |
| RAM | 512 KB 80 ns VRAM |
IBM PS/2 8525SX (link)
| Year | 1991 (?) |
| Video Chip | IBM 84F7985 IBMVGA256c |
| RAMDAC | INMOS IMSG171P
? MHz 8-bit DAC up to 256 colors from a total of 262,144 colors |
| RAM | 512 KB 80 ns VRAM |
IBM PS/2 Thinkpad 700C/720C (pic 1) (pic 2)
| Year | 1992 |
| Video Chip | IBM 39G8600 IBMVGA256c |
| Clock Chip | ICS ICS2494
135 MHz Dual Video/Memory Clock Generator for VGA, Super VGA, XGA
video adapters, 8514A, TMS34010, TMS34020 |
| RAMDAC | ? MHz on chip? |
| RAM | 512 KB 80 ns VRAM |
IBM SVGA Adapter/A (link) (pic)
| Year | 1992 (together with Server 85) |
| Video Chip | IBM 42G3410 (= TI CF63011PCM) IBMVGA256c |
| unknown | IBM 85F0120 (= OKI M7U016-008) |
| Clock Chip | ICS ICS2494
135 MHz Dual Video/Memory Clock Generator for VGA, Super VGA, XGA
video adapters, 8514A, TMS34010, TMS34020 |
| RAMDAC | INMOS IMSG176J-80Z
80 MHz 8-bit DAC up to 256 colors from a total of 262,144 colors |
| RAM | 512 KB 80 ns VRAM |
Driver Support
DOS
Generic: r700c120.exe
SVGA/A: m95svga.exe
VESA/VBE driver*
256 KB VRAM, at least 40 MHz RAMDAC 800x600 pixels, 16 colors, 60 Hz**
512 KB VRAM, at least 30 MHz RAMDAC 640x480 pixels, 256 colors, 60 Hz
512 KB VRAM, at least 40 MHz RAMDAC 800x600 pixels, 265 colors, 60 Hz**
512 KB VRAM, at least 50 MHz RAMDAC 1024x768 pixels, 16 colors, 43 Hz I***
256 KB VRAM, at least 30 MHz RAMDAC 132-column x 25-row text
Notes:
* RAMDAC requirements are calculated with the following formula:
line frequency in kHz = ([vertical resolution] *
[horizontal refresh rate] Hz + [vertical resolution] *
[horizontal refresh rate] Hz * 0,1)/1000
RAMDAC pixel frequency in MHz = ([horizontal resolution]
* [line frequency] kHz + [horizontal resolution] * [line
frequency] kHz *0,2)/1000
** the IBMVGA256c chipset does 800x600 pixels, 56 Hz
too but LCDs usually don't support refresh rates below
60 Hz and you will not accept a 56 Hz refresh rate on aCRT
monitor.
*** LCDs usually don't support an interlaced video
resolution. 1024x768 pixels,16 colors, 60 Hz requires at
least a 70 MHz RAMDAC
OS/2
From v2.11 up build in under the name "IBM VGA 256c".
640x480 pixels, 256 colors with 512 KB VRAM, at least a 30 MHz RAMDAC.
A higher resolution may be possible according to
THIS
page.
Windows 3.1x
Generic: r700c120.exe
640x480 pixels, 256 colors w/ 512 KB VRAM, at least a 30 MHz RAMDAC together
with DOS VESA/VBE software driver.
| 
