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Well, "difficult" usually goes away when you have lots of time, so I have to add ship pressure. If you have time, then hard goes away. Making the Newton data s

by kabdib 13y ago

Well, "difficult" usually goes away when you have lots of time, so I have to add ship pressure. If you have time, then hard goes away. Making the Newton data stores stable, about three months before we shipped. The Newton had a flash-based object store instead of a file system, and the code was such that a power loss or a reset in the middle of an update would toast your data. I spent about six 100+ hour weeks writing a transaction system to make sure that users wouldn't lose data to a crash or a dead battery. I think I had to fix only a couple of bugs in that code, after a massive checkin. Then, making the audio pipeline for the Kinect stable enough for noise cancellation to work. I'd heard that doing isochronous audio was hard, and "yeah, yeah, sure," but I had no idea it was really hard until I'd shipped a system that used it, with tight constraints around latency variance. I worked with some really good people on this, and there were days when we were looking at Xbox hypervisor code, application code and even DMA traffic on the camera itself. Another three or four 100+ hour weeks, maybe three weeks before we shipped, changing scary stuff everywhere. I still remember a satisfying feeling when I discovered the exact buffer we needed to use as a clock root for audio (and it wasn't the obvious one).

wrs 13y ago
And while you were doing that, I was finishing the indexed object store on top of that transactional layer. I spent at least a week starting the stress test, going to bed, waking up, reading the test log and fixing bugs, starting the test, going to bed... (Shouldn't have started with someone else's half-baked B-tree code!) Somehow the Newton team managed to do a whole stack of things like that in a ridiculously short time, and then shipped them in read-only memory -- not Flash, kids, but for-keeps permanently masked ROM -- and it worked. I've never seen anything like it since.
- kabdib 13y ago
  That was fun. Let's do it again :-) [That same B-tree code was powering our source code control system, IIRC. Every time we hit the next power of two on the database size something else would explode. Wheee.] Patching the mask ROMs was fun. Nope, you can't change those things, but we had a bunch of bugs to fix between the time the ROMs taped out and we actually shipped. We couldn't afford a full ROM jump table (the newt had 4MB of ROM, 512K of RAM, and we ran the heaps mostly full and had essentially no memory left), so we randomized the jump table and played aliasing games with page mapping to get our patch budget down to 20K or so. It helped to have really good engineers -- people who really got into the swing of twisted, devious code -- write the patches. I wrote a couple of fixes, and had done a pretty good job, I thought, then handed them to Andy S. who always came back with something about five instructions long that worked better and maybe fixed another bug, too, with a bonus cackle of maniac laughter. When I started, Newton was an expensive researchy pipe-dream. A year later we'd done a complete reset and shipped product it. I don't know how we did that.

by kabdib 13y ago

wrs 13y ago

And while you were doing that, I was finishing the indexed object store on top of that transactional layer. I spent at least a week starting the stress test, going to bed, waking up, reading the test log and fixing bugs, starting the test, going to bed... (Shouldn't have started with someone else's half-baked B-tree code!) Somehow the Newton team managed to do a whole stack of things like that in a ridiculously short time, and then shipped them in read-only memory -- not Flash, kids, but for-keeps permanently masked ROM -- and it worked. I've never seen anything like it since.

kabdib 13y ago
That was fun. Let's do it again :-) [That same B-tree code was powering our source code control system, IIRC. Every time we hit the next power of two on the database size something else would explode. Wheee.] Patching the mask ROMs was fun. Nope, you can't change those things, but we had a bunch of bugs to fix between the time the ROMs taped out and we actually shipped. We couldn't afford a full ROM jump table (the newt had 4MB of ROM, 512K of RAM, and we ran the heaps mostly full and had essentially no memory left), so we randomized the jump table and played aliasing games with page mapping to get our patch budget down to 20K or so. It helped to have really good engineers -- people who really got into the swing of twisted, devious code -- write the patches. I wrote a couple of fixes, and had done a pretty good job, I thought, then handed them to Andy S. who always came back with something about five instructions long that worked better and maybe fixed another bug, too, with a bonus cackle of maniac laughter. When I started, Newton was an expensive researchy pipe-dream. A year later we'd done a complete reset and shipped product it. I don't know how we did that.