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Ah, the Jaguar... (Score:5, Interesting)
by John Carmack on Saturday March 04, @09:18PM EST (#119)
(User Info)
I actually dug up all my old jaguar development hardware to give to these guys a year or two ago.
Unfortunately, it turned out that I had lost the C compiler that I had retargeted to the jaguar RISC
engines, so DOOM was no longer buildable.
There is something noble about developing on a dead platform -- it is so completely for the joy of the
development, without any commercial motivation.
The quick recap on the jaguar:
The memory, bus, blitter and video processor were 64 bits wide, but the processors (68k and two
custom risc processors) were 32 bit.
The blitter could do basic texture mapping of horizontal and vertical spans, but because there wasn't
any caching involved, every pixel caused two ram page misses and only used 1/4 of the 64 bit bus.
Two 64 bit buffers would have easily trippled texture mapping performance. Unfortunate.
It could make better use of the 64 bit bus with Z buffered, shaded triangles, but that didn't make for
compelling games.
It offered a usefull color space option that allowed you to do lighting effects based on a single channel,
isntead of RGB.
The video compositing engine was the most innovative part of the console. All of the characters in
Wolf3D were done with just the back end scalar instead of blitting. Still, the experience with the
limitations and hard failure cases of that gave me good amunition to rail against microsoft's (thankfully
aborted) talisman project.
The little risc engined were decent processors. I was surprised that they didn't use off the shelf
designs, but they basically worked ok. They had some design hazards (write after write) that didn't get
fixed, but the only thing truly wrong with them was that they had scratchpad memory instead of
caches, and couldn't execute code from main memory. I had to chunk the DOOM renderer into nine
sequentially loaded overlays to get it working (with hindsight, I would have done it differently in about
three...).
The 68k was slow. This was the primary problem of the system. You options were either taking it
easy, running everything on the 68k, and going slow, or sweating over lots of overlayed parallel asm
chunks to make something go fast on the risc processors.
That is why playstation kicked so much ass for development -- it was programmed like a single serial
processor with a single fast accelerator.
If the jaguar had dumped the 68k and offered a dynamic cache on the risc processors and had a tiny
bit of buffering on the blitter, it could have put up a reasonable fight against sony.
Now the LYNX, on the other hand, was very much The Right Thing from a programming standpoint.
A fast little processor (for its niche), a good color bitmapped display, and a general purpose blitter.
Price and form factor weighed too heavily against it.
John Carmack
Re:Ah, the Jaguar... (Score:1)
by Thunderbirds (thunderbird_ANTISPAM_@sprynet_SPAMSUX_.com) on Saturday March 04,
@09:46PM EST (#125)
(User Info) http://home.sprynet.com/~thunderbird
Actually, I believe you're referring to Carl Forhan of Songbird Productions. He's the guy who you
gave your development systems and DOOM source code to.
He's been trying to come up with a revival of the DOOM code with another fellow.
Carl is the guy who's been publishing an additional 4 "complete but never published" Jaguar titles
which someone else here already mentioned.
The problem you mention with the Jaguar being unable to run from system RAM was actually a bug
in the memory controller. It was intended to be able to run from main RAM. There were quite a
number of these (fairly crippling) bugs in the hardware, and we had to work around them to get
BattleSphere completed. The fact that it runs at all is pretty amazing... (I'm not sure if this is
something to be proud of or not.)
Doug "Thunderbird" Engel BattleSphere Assistant Coder & Lead Artist Scatologic
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Re:Ah, the Jaguar... (Score:2)
by John Carmack on Saturday March 04, @09:55PM EST (#127)
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>Actually, I believe you're referring to Carl Forhan of Songbird Productions
Heh, sorry... I just assumed all jaguar development was coming from a single crazy group. :-)
Even if the memory controller hadn't been broken, performance would still have sucked really bad
without a cache.
The jaguar was definately significantly hampered by its technical flaws, which kept me from ever
being too big of a jaguar booster. I was proud of my work on Wolf and DOOM (more so than just
about any of the other console work Id has been involved in until just recently), but in the end, the
better consoles won the war.
John Carmack
