[rescue] octane question

[Big Endian]

>On Mon, Jan 14, 2002 at 03:16:10PM -0500, Big Endian wrote:
>>  >Err, you have an octane don't you?  What is it's graphical setup?
>>
>>  No I don't but I've dealt with IMPACT indigo2s and I've done a LOT of
>>  research on the octane (read mental masturbation over the octane).
>>  The *I cards on the octane are repackages of the IMPACT cards for
>>  indigo2s and use XIO instead of GI)64.  Octanes w/ MXI graphics
>>  report "4 TRAMS" to /usr/gfx/gfxinfo and hinv.  If anybody has seen
>>  differently I would *LOVE* to be proven wrong (and then grab an MXI
>>  octane).  The nice thing about XIO is the raw throughput
>>  (800mb/sec/direction burst)  so you can *STREAM* textures in and out
>>  of ram.  This is hard to do w/ a lesser machine or even a greater
>>  machine (EBUS is 1.2GB/sec but its a shared bus and I'm not sure if
>>  thats a full duplex figure).
>
>I don't know what EBUS is, but on the O2 you are always streaming textures in
>and out of RAM.  That it was designed to do that well is what makes 
>it superior
>for doing things like volumetric vizualization and image processing.
>

EBUS=PowerPath2=Challenge/Onyx bus.  The distinction of the O2 is 
that it doesn't actually have seperate memory systems.  Its a UMA 
machine so that framebuffer is just a segment of the main ram.  While 
a common sight on PCs (i810, etc) that don't require high speed 
graphics the O2 has pulled this off with TREMENDOUS success. 
Primarily due to the fact that memory moves at 2.1GB/sec on an O2 
(move the ENTIRE memory capacity of the damn thing in .5 secs, kick 
ass).  So an O2 has *VERY* little work to do in streaming textures as 
it has as much tram as it can fit into main memory.

>  > >I'll have to write up a sample program to test what the capabilities
>>  >of octanes
>>  >with low/no TRAM are one of these days.
>>
>>  You can still get CPU based texturing on the SI and SSI cards.  I'm
>>  sure that it sucks... but you can do it.  The O2, even with all the
>>  stuff they do on the CPU *HAS* hardware texture because CPU texture
>>  sucks.  I wouldn't bother testing w/ no TRAMS.
>
>Well, there are two questions.  An SSI + TRAM has hardware texturing.  We are
>led to believe that the TRAM is texture ram.  So, the first question is TRAM
>just texture ram?  The second question is does the SI have hardware texturing?
>As the O2 shows, you can have hardware texturing without texture ram, and if
>the TRAM is just ram, then that would mean that the SI would have to have
>hardware texturing.  And with this we are left asking if the TRAM is just ram
>and the SI has hardware texturing, is there a software setting forcing it off
>(ie making it act like there is no hardware texturing when no TRAM 
>is sensed so
>that they can badget you to spending $$$ on a TRAM that doesn't really do any-
>thing anyway since your textures are too large).

Octane *I series graphics don't have hardware texture w/o TRAM.  The 
RM chips are there but they can't support texture from main ram (too 
slow... the TRAM on IMPACT is RAMBUS similar to the N64 ram, 400mhz, 
16bits wide (3.2GB/sec)(from memory, not sure the exact specs, please 
fill me in here).  This memory is local to the card. An SI - TRAM has 
no hardware texture, but an SI + TRAM does.  Same with the SSI 
(double the geometry and pixel power of the SI) as it becomes MXI w/ 
TRAM.  The IMPACT TRAMS are *REALLY* expensive to make (remember 
rambus ram for the P4?) especially 6 years ago, its almost a cache 
made of DRAM instead of SRAM.  The O2 uses *MAIN MEMORY* for 
everything(framebuffer,texture storage/cache, AND main system ram) as 
it is local to everything (CPU,ICE, and CRM).  So it does have 
texture memory... just a variable amount of it.  And I don't recall 
if there is a way to measure it.

>A sample program is usefull to make sure that the texture streaming actually
>works adquately on the Octanes with the cheapest texturing option. 
>And once it
>is written, why not ask someone with superplane SI graphics to give it a test
>run?  Worst case is that it would be slow, and we would know not to count on
>getting a useable Octane for less than $1k.

This is something to count on if you need texture.  This is why I got 
a Crimson for doing high end graphics work that wasn't cpu intensive. 
2RM RE is *VERY* nice even w/ a 64MB/sec bus.  These benchmark almost 
as fast (and 10 times better quality) as an SI+TRAM at $285 (still 
have some VGXT crimsons left people, PLEASE relieve me of them they 
are all 150mhz, might have 256mb ram, and they come w/ drivesleds.).

daniel
-- 
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"Fragile. Do not drop." -- Posted on a Boeing 757.