Power Series/Crimson VGX and VGXT
Last Update: October 6, 1999

Pictures of a Power Series 4D/510 VGX

VGX/VGXT Board Revisions

VGX/VGXT Features and Capabilities

Just how good is the VGX/VGXT graphics boardset?

Performer and VGXT

Other VGX/VGXT Links


Pictures of a Power Series 4D/510 VGX

These pictures show a 5-span (one RM2/3) Power Series VGX with an IO3B and a Crimson R4000/100 IP17. I have both the VGX and VGXT boardsets but they are visually identical.

 The populated card cage. The slots and cards are as follows:
 
VME Slot 1 Empty (Dead RM4 - ignore).
VME Slot 2,3,4,5,6 Empty
Slot 7 IO3B
Slot 8 IP17 R4000/100MHz SC board with 208Mb RAM
Slot 9-11 Empty
Slot 12 MC2 memory board
Slot 13 MC2 memory board
Slot 14 GM3 graphics manager
Slot 15 GE6 geometry engine
Slot 16 Empty (could be an RV2 video option card)
Slot 17 Empty (could be another RM2/RM3)
Slot 18 RM2/RM3 Raster Manager
Slot 19 DG1 Display Generator

The boardset I have shown here is a minimum/low end VGX config. I have a VGXT config as well in a power series twin tower machine.

Close up of the VGX card set and bridge boards. Notice that DG1 (in slot 19) has 5 video I/O ports and that the RGB I/O panel connector is plugged into the third. What are the other ports for? Numbered from the top the ports are as follows:

  1. GENLOCK sync
  2. Alpha output Video
  3. RGB video output and sync to monitor
  4. Super VHS and composite video
  5. GENLOCK input

VGX/VGXT Board Revisions

VGX Boardset
 
GE6 - Geometry Engine 030-0153-004B (Texas Instruments 74ACT8867)
GM3 - Graphics Manager 030-0382-004A (doesnt work with RM3s!)
RM2 - Raster Manager 030-0156-004B (IMP3 image engines 20 per board)
DG1 - Display Generator 030-0158-004D

/usr/gfx/gfxinfo -v

Graphics board 0 is "VGX" graphics.
    Managed (":0.0") 1280x1024
    5 spans,   IMP3
    EV mask = 0x0
    1 screen(s) on this pipe
    GM bi-endian ready

VGXT Boardset
 
GE6 - Geometry Engine 030-0153-004B (Texas Instruments 74ACT8867)
GM3B - Graphics Manager 030-0232-001B
RM3 - Raster Manager 030-0222-001C (IMP5 image engines 20 per board)
RM3 - Raster Manager 030-0222-001C (IMP5 image engines 20 per board)
DG1 - Display Generator 030-0218-004C

/usr/gfx/gfxinfo -v

Graphics board 0 is "VGX" graphics.
    Managed (":0.0") 1280x1024
    10 spans,   IMP5
    EV mask = 0x0
    1 screen(s) on this pipe
    GM bi-endian ready


Features and Capabilities of VGX/VGXT

From recent discussions on VGX/VGXT (also known as POWERVision) in comp.sys.sgi.hardware, the POWERSeries Technical Report and some searches through the info-performer archive, here are some snippets of information about VGX and VGXT:

The following texture tables are reproduced from an info-performer message in April 1994 sent by David Marsland (then mars@csd.sgi.com):

VGX Texture Memory Tile Summary
 
texture tile size non-mipmapped
size in bytes (k) of each tile
5-span, 64k texel config 10-span, 160k config mipmapped size in bytes (k) of each tile 5-span, 64k texel config 10-span, 160k config
16x16 352 186 465 512 128 320
32x32 1184 (1.16k) 55 137 1664 (1.62k) 39 97
64x64 4384 (4.28k) 14 35 6016 (5.88k) 10 25
128x128 16928 (16.53k) 3 7 22912 (22.38k) 2 5
256x256 66592 (65.03k) 1* 2* 84972 (87.38k) 0
512x512 264224 (258.03k) 0 0 353664 (345.37k) 0 0

* - VGX requires special microcode to support 256x256 texture tiles (this is probably included in all releases after 1994 that support VGX - not sure about 4.0.5 etc but definitely 5.2, 5.3 and 6.2)
 

VGXT Texture Memory Tile Summary
 
texture tile size non-mipmapped
size in bytes (k) of each tile
5-span, 64k texel config 10-span, 160k config mipmapped size in bytes (k) of each tile 5-span, 64k texel config 10-span, 160k config
16x16 256 256 640 352 186 465
32x32 1024 (1k) 64 160 1376 (1.34k) 47 119
64x64 4096 (4k) 16 40 5472 (5.34k) 11 29
128x128 16384 (16k) 4 10 21856 (21.34k) 2 7
256x256 65536 (64k) 1 2 87392 (85.34k) 1
512x512 262144 (256k) 0 0 349536 (341.34k) 0 0


Just how good is the VGX/VGXT graphics boardset?

According to the graphics specs on Ian Mapleson's web site, VGXT is fairly close to RealityEngine when it comes to non-textured graphics - see http://www.futuretech.vuurwerk.nl/gfxtables.html. However, it's difficult to do a "hard numbers"  comparison at the moment. Open Inventor (or any other OpenGL based test suite) isnt really much use as:

In order to get some idea of VGXT performance, I installed performer and tried out the demonstrations - you can see the results plus a more detailed discussion of the features provided by VGXT on the performer and VGX page. I also ran skyfly which is quite a nice fly thru demonstration where you chase yellow paper planes over a textured river valley and hills (a snap from skyfly is shown as a colour plate in the OpenGL 1.1 red book!) Interestingly, the skyfly demo would not run on VGX! It complained about requiring a skywriter (ie. at least one VGXT pipe) and then exited.

An interesting and rare config involving the VGX/VGXT is the Power Series dual VGX/VGXT SkyWriter machine. This machine had an optional display multiplexer (the DG/VX1 - see above) and two VGXT graphics boardsets. As I understand it, the VGXT boardsets generated alternate frames and the mulitplexer combined the alternate frames to produce a single display (cyclops mode?). The effect was probably quite good - unfortunately there are very few SkyWriter cabinets around so its almost impossible to do any tests (but see the links section below for pictures of this rare beast).


Other VGX/VGXT Links

For pictures of a dual pipe (two VGXT boardsets) Power Series SkyWriter case see SkyWriter's site at: http://www.reputable.com/~skywriter. SkyWriter also has the SGI skywriter technical report available on his site now. Definitely worth a read for skywriter enthusiasts!
 

Comments to: simon@dpiwe.tas.gov.au