感觉这才是值得做的编程工作啊！吾辈当自勉

https://news.ycombinator.com/item?id=42465378

Xbox 360 的一位软件工作者也来发了个帖子：

One challenge was that while I started working on the Xbox 360 about three years before it would ship, we knew that the custom CPU would not be available until early 2005 (first chips arrived in early February). And there was only supposed to be one hardware spin before final release.

一项挑战是，我是在 XBox 360 发售三年前开始给它写代码的（这位程序员当时写的是 bootloader 、kernel 和 hypervisor ）。我们知道要等到 2005 年年初才能拿到芯片。

So I had no real hardware to test any of the software I was writing, and no other chips (like the Apple G5 we used as alpha kits) had the custom security hardware or boot sequence like the custom chip would have. But I still needed to provide the first stage boot loader which is stored in ROM inside the CPU weeks before first manufacture.

但是我仍然需要在开始生产之前数周的时候就拿出 bootloader 的代码，用以在生产之时保存在 ROM 中。

I ended up writing a simulator of the CPU (instruction level), to make progress on writing the boot code. Obviously my boot code and hypervisor would run perfectly on my simulator since I wrote both!

于是我最后写了一个指令级的 CPU 模拟器，用来帮助我的编程工作。我的 bootloader 和 hypervisor 在模拟器上运行的很完美。

But IBM had also had a hardware accelerated cycle-accurate simulator that I got to use. I was required to boot the entire Xbox 360 kernel in their simulator before I could release the boot ROM. What takes a few seconds on hardware to boot took over 3 hours in simulation. The POST codes would be displayed every so often to let me know that progress was still being made.

IBM 也提供了一个硬件加速的、能够精准到时钟周期的模拟器。我需要在烧录 ROM 之前在这个模拟器上成功运行整个 XBox 360 的 kernel 。在硬件上只需要几秒钟就能开机，但是在 IBM 提供的模拟器上却需要三个小时才能完成整个开机过程。为了显示开机程序还在运行，自检代码每隔一会就会在屏幕上出现。

The first CPU arrived on a Friday, by Saturday the electrical engineers flew to Austin to help get the chip on the motherboard and make sure FSB and other busses were all working. I arrived on Monday evening with a laptop containing the source code to the kernel, on Tuesday I compiled and flashed various versions, working through the typical bring-up issues. By Wednesday afternoon the kernel was running Quake, including sound output and controller input.

第一块 CPU 周五运到。周六硬件工程师飞到 Austin 去帮助把它安装在主板上，并保证总线正常工作。我是周一晚上赶到的，随身带了一台笔记本电脑，上面有 kernel 的代码。到了周二，代码编译好并烧录进机器，到了周三下午就能够跑 Quake 了，包括声音输出和摇杆输入。

Three years of preparation to make my contribution to hardware bring-up as short as possible, since I would bottleneck everyone else in the development team until the CPU booted the kernel.

关于这位大牛自己写的模拟器（指令级别）的一些趣闻：

I called the simulator Sbox and it was just a simple console app. I didn't implement the GPU, so no graphics just the hypervisor and kernel and some simple non-graphics apps. I made it so that you could build the Xbox 360 kernel on your windows machine, then just run sbox.exe and it would automatically find the just built kernel image targeting the PPC64 and boot it. Then if you typed control-C it would drop into the kernel debugger as a sub process, and you could poke around at the machine state as if it were the real Xbox hardware, showing all the PPC instructions and registers. It was a lot of fun writing it, and quite useful.

我把它叫做 Sbox 。它不模拟 GPU ，所以没有图像，只有 hypervisor 和 kernel 以及一些简单的文字程序。开发团队能够在 Windows 上编译 Xbox 360 内核，然后运行 sbox.exe ，它就能自动找到刚刚编译好的针对 Power PC 的内核二进制文件，并在模拟器内部开机。如果你输入 Ctrl-C ，那么就能进入到 kernel debugger 的子进程，勘察（模拟）机器的状态，包括所有 Power PC 指令和计算器，就好像这是一台真正的 XBox 360 一样。

（以下是大牛的一位同事说的）

You should also talk about the lwarx/stecx bug. IIRC - in the first version of the chip there was a bug in one or both of these instructions. Your code booted on SBox but didn't on the hardware. You compared the two and then figured out it was these instructions. You filed a bug report and then dug into them and used SBox to figure out what must have been going wrong.

你应该谈谈 lwarx/stecx bug 。我没记错的话，第一版的芯片有这个 bug 。你的代码能够在 Sbox 上运行，但是不能在硬件上运行。你在对比了两者之后，分析出是这两个指令的问题。你（给 IBM ）递交了一份 bug 报告。

The chip supplier came back with a workaround and within five minutes you simulated it on SBox and said it wouldn't work, why, and then said how it should be fixed.

IBM 送了一块新的芯片过来，你在 SBox 上跑了五分钟之后就说它肯定不行，应该怎么样怎么样才能解决这个问题。（我读下来的感觉是，IBM 仅仅是提供了一个 workaround ，然后大牛在 SBox 里模拟了这个 workaround ，发现还是不行）

The supplier didn't believe you as yet. And you worked out a workaround so we could be unblocked. Two weeks later they agreed with your fix...

IBM 不相信你的话，于是你自己想了个解决办法，避免我们的进度停滞不前。两个礼拜之后 IBM 说你的解决办法没错。