G
Guest
http://news.teamxbox.com/xbox/8357/MS-Engineer-Speaks-on-Xbox-360-Backward-Compatibility/
blog http://www.qbrundage.com/michaelb/pubs/essays/xbox360.html
quote:
"Now that it's been announced at E3, I can finally reveal that the Xbox 360
feature I work on is... Xbox backwards compatibility!
Yes, it's real. It's been fun to watch all the wild speculation over the
past year or so as to whether the Xbox 360 would or wouldn't be backwards
compatible. And reading all the crazy ideas people have about how hard or
easy it would be.
Xbox backwards compatibility is a unique project in so many ways, and I feel
very fortunate to get to work on it. I'm sure it will be the hardest
technical challenge of my career -- I can't imagine what could possibly top
it in terms of sheer technical difficulty. It's not just the difficulty of
emulating completely different processors and devices. It's also all the
arcane knowledge I've needed to acquire about kernel-level development,
advanced graphics processing, operating systems and computer architectures.
It's changed the way I think about software.
To me, the most appealing aspect of backwards compatibility is its "magical"
quality. Normally, once you understand how something magical works, it's
much less amazing. With Xbox backwards compatibility, the opposite is
true -- the more you understand what it needs to do, the more certain you
are that it's impossible, and consequently the more amazed you are to see it
in action.
For example, some people observe the CPU and GPU architectures are utterly
different between the Xbox 360 and the Xbox, and then speculate about the
difficulties those differences pose for emulation. Without really
understanding anything that's involved, they're already convinced that
backwards compatibility is a difficult task.
Others apply more knowledge and compare the situation to something familiar,
such as existing x86 emulators for PPC. For example, Virtual PC for Mac is
great for many tasks, but gaming isn't one of them. On my 1.25 GHz
Powerbook, VPC 7 emulates a 295 MHz PC. Even solitaire feels slow, let alone
anything graphically challenging. And the Xbox isn't just any x86 machine,
it's a computing powerhouse. Emulating it seems beyond today's technology.
Other people compare the Xbox 360 against the Xbox
When I look at these numbers, I think: Wow! The Xbox is already a very
powerful machine, and the Xbox 360 blows it away. The Xbox 360 will be
fantastic for high-definition gaming!
But emulation is a difficult challenge any time the emulator isn't several
orders of magnitude faster than what it's emulating. So a few people who
understand how emulators work look at these numbers, impressive as they are,
and conclude that Xbox backwards compatibility will not work. (And then when
they see backwards compatibility working, they realize the Xbox 360 is even
more impressive than they thought!)
Finallly, there are a very few people who understand both Xbox systems
inside and out to an expert level of detail that I'm not about to go into
here. They perform more sophisticated calculations using the Art of Software
Engineering, but ultimately reach the same conclusions as those not skilled
in the Art: Backwards compatibility is impossible. One such skeptic
interviewed me for my current job, and pointedly asked during the interview
how I planned to handle the project's certain future cancellation.
And yet, here it is. It's magic!
This is part of what makes working at Microsoft so much fun -- the
opportunity to work on magical projects and do the impossible. It's a lot of
hard work, of course, but the challenge makes it fun."
blog http://www.qbrundage.com/michaelb/pubs/essays/xbox360.html
quote:
"Now that it's been announced at E3, I can finally reveal that the Xbox 360
feature I work on is... Xbox backwards compatibility!
Yes, it's real. It's been fun to watch all the wild speculation over the
past year or so as to whether the Xbox 360 would or wouldn't be backwards
compatible. And reading all the crazy ideas people have about how hard or
easy it would be.
Xbox backwards compatibility is a unique project in so many ways, and I feel
very fortunate to get to work on it. I'm sure it will be the hardest
technical challenge of my career -- I can't imagine what could possibly top
it in terms of sheer technical difficulty. It's not just the difficulty of
emulating completely different processors and devices. It's also all the
arcane knowledge I've needed to acquire about kernel-level development,
advanced graphics processing, operating systems and computer architectures.
It's changed the way I think about software.
To me, the most appealing aspect of backwards compatibility is its "magical"
quality. Normally, once you understand how something magical works, it's
much less amazing. With Xbox backwards compatibility, the opposite is
true -- the more you understand what it needs to do, the more certain you
are that it's impossible, and consequently the more amazed you are to see it
in action.
For example, some people observe the CPU and GPU architectures are utterly
different between the Xbox 360 and the Xbox, and then speculate about the
difficulties those differences pose for emulation. Without really
understanding anything that's involved, they're already convinced that
backwards compatibility is a difficult task.
Others apply more knowledge and compare the situation to something familiar,
such as existing x86 emulators for PPC. For example, Virtual PC for Mac is
great for many tasks, but gaming isn't one of them. On my 1.25 GHz
Powerbook, VPC 7 emulates a 295 MHz PC. Even solitaire feels slow, let alone
anything graphically challenging. And the Xbox isn't just any x86 machine,
it's a computing powerhouse. Emulating it seems beyond today's technology.
Other people compare the Xbox 360 against the Xbox
When I look at these numbers, I think: Wow! The Xbox is already a very
powerful machine, and the Xbox 360 blows it away. The Xbox 360 will be
fantastic for high-definition gaming!
But emulation is a difficult challenge any time the emulator isn't several
orders of magnitude faster than what it's emulating. So a few people who
understand how emulators work look at these numbers, impressive as they are,
and conclude that Xbox backwards compatibility will not work. (And then when
they see backwards compatibility working, they realize the Xbox 360 is even
more impressive than they thought!)
Finallly, there are a very few people who understand both Xbox systems
inside and out to an expert level of detail that I'm not about to go into
here. They perform more sophisticated calculations using the Art of Software
Engineering, but ultimately reach the same conclusions as those not skilled
in the Art: Backwards compatibility is impossible. One such skeptic
interviewed me for my current job, and pointedly asked during the interview
how I planned to handle the project's certain future cancellation.
And yet, here it is. It's magic!
This is part of what makes working at Microsoft so much fun -- the
opportunity to work on magical projects and do the impossible. It's a lot of
hard work, of course, but the challenge makes it fun."