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Name: Jim Thompson
Member since: 2000-11-30 13:53:00
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Homepage: http://jimthompson.org


In addition to the projects listed below, I am the original developer of the Emacs package ps-print that converts fontified Emacs buffers into PostScript, preserving font information -- in other words, a pretty-printer. I no longer maintain or work on ps-print, but to date it's my only lasting contribution to the world of free software.

More recently, I have developed a strong interest in digital photography, and in making free software tools to work with digital cameras, and to manage and present digital photos. The two projects below reflect this interest:


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ODS version 0.9 is almost ready to release! I had planned to get it out this weekend, but had my plans changed for me. Here's the story, as written up for a non-technical friend:

The weekend got off to a great start. I finally figured out the problem with the new network and had it functioning as well as could be expected. The parts had arrived earlier in the week: a new 100 megabit network hub, and three network cards to go in the PCs. I had put the new cards in the computers, connected the cables to the new hub... but it wouldn't work... at least not at the 100 megabit speed, though it would still work at the slower 10 megabit speed. At the higher speed, I couldn't even ping one machine from the other.

Friday night I had finally figured out the problem: it was my homemade network cables. I had been crimping the connectors onto the cables the wrong way. Once I had this figured out, I got out my knife and crimping tool, snipped the old connectors off all the cables, and crimped new connectors on them all. I didn't have that many to recrimp, but it took me most of the night because I'm slow. I was especially glad when the cable I had run through the attic, connecting the server in my study to the PC in the play room, finally worked correctly. Pulling that cable through the attic had been a real headache, and I wasn't looking forward to having to replace it.

I was up until the wee hours Friday, but when I was done, the network was working well. All the cables had been tucked neatly away. The test cables, including the temporary that had been laying stretched on the floor between my study and the playroom, were tidily coiled and stowed away for future use. And the new network hub was sitting in its new home on the shelf, warm and cozy, its "100" lights all lit up and blinking happily as the computers talked. I went to bed sometime around 3:00 AM, feeling good.

During the night, disaster struck.

I got up Saturday morning expecting finish writing the manual for my camera software so I could finally release it to the world. But my server was in an odd state: system load was extremely high, and it was unresponsively slow. It appeared to respond to mouse movement, but I couldn't bring up a process list to see who was hogging the CPU. Finally, I switched to the console window and saw an endless list of disk errors spewing out the error log. Uh-oh.

Trying hard not to panic, I attempted to shut down the system, but with the disk not working, I couldn't shut it down normally. I had to just turn the power off. Now, this is a bad thing to do on a Windows box, and it's even worse on a linux machine, but I had no choice. Things weren't looking good.

They got even worse when I tried to restart the machine. One of the disk drives wouldn't respond at all. It was a 9 Gigabyte Ultra-2 SCSI drive: relatively new, the fastest disk in my system. I tried repeatedly to get the drive online, and as I did, I began to get that sick feeling in the pit of my stomach. The drive wouldn't respond.

Eventually I experienced a brief moment of hope as I got the drive to talk to the SCSI controller again. It wasn't dead, it was just badly injured! If I could get the drive online again, even for just a little bit, I could dump its contents onto tape and rescue my information before the drive died complelety. I fumbled through my tape bin looking for some empties to dump onto. But my efforts were in vain: the drive wouldn't go back online. It would talk to the SCSI controller, but could only say that it had an internal error. Its injuries had left it brain-dead, and I would get nothing more out of it.

At this point, panic began to look more and more like a viable option. Trouble was, I wasn't exactly sure what to panic over. On Windows system, you have C: and D: drives, etc. These drive letters usually correspond one-to-one to the separate pieces of hardware installed in your machine. Your A: drive is your floppy. If you have one hard drive, it's your C: drive. If you have a second hard drive, it's your D: drive. If you have a CDROM, it'll then be E: drive.

On any type of unix system, these distinctions are hidden from you; all the different drives are merged seamlessly into one huge filesystem. You don't see the boundaries between one disk and the next, You don't think in terms of which "drive" your information is on, you just think about its directory -- its location in the hierarchy. Eventually you tend to forget about the fact that all this information is really stored on separate pieces of hardware; it's just one large happy collection of information.

This is fine for day-to-day work, but it's an incredible hindrance when you want to panic. I couldn't remember exactly what had been stored on that 9 GB disk drive. I wanted to run about the house screaming "oh my god I've lost all my ________", but I wasn't sure whether to fill in the blank with "e-mail" or "software" or "snapshots" or "porn" or "secret Nixon audio tapes" or what!

Eventually, I began to settle down and think again. I booted my linux rescue CD, and so I could look at the remaining good disk drive and figure out, through process of elimination, what I had lost. I got the good drive mounted, looked through its contents, and found my home directory. So I hadn't lost any e-mail. I had lost my operating system and my archive of digital photos. Brain beginning to function again, I remembered that I had a tape machine, so I probably had backups. Checking the shelf, I found backup tapes. I was finally beginning to see a way out of all this mess.

I won't talk you through the rest of it step by step, but suffice to say that I spent most of the next 24 hours just bootstrapping a running system. I found two unused old disk drives, and I had to take my system almost completely apart to extract the old drive and find places for the two replacements. I was able to recover a functional operating system from tape; my most recent backups were from July of last year, but not much had changed since then, so my system is almost fully back to normal.

That was Saturday. In getting the new system running again, I'd needed access to the innards of the system, and the best way was just to lay the drives out on the floor, connect their cables, and let them run that way. When I finally got my system up and running again, having worked through the night, it was 7AM and I was too tired to reassamble it. Sunday I spent reassembling my system and cleaning up the mess.

The most critical item on the dead drive is the lost collection of digital photos because they're irreplaceable. The backup tape is from July of last year. Fortunately, I haven't taken many photos since then, and what photos I have taken are still in the camera. So it looks like I might not have lost much... assuming my backup tape is good. I'll try to recover those sometime this week.

18 Dec 2000 (updated 18 Dec 2000 at 07:47 UTC) »

Vacation! Three glorious weeks of nothing to do but sit around the house and work on personal projects. No emulator bugs to fix, no new emulator features to think about. Actually, it's now two weeks of vacation; I spent the first week trying to finally sleep off this nagging cold (it's still with me) and generally being lazy.

Like I do for most vacations, I have made myself a long list of things that urgently need doing and, like most vacations, the majority of them will go undone. I've started on a couple of the projects: the update of jimthompson.org and the release of ODS. I expect to get ODS out before Christmas; likewise, my web site should soon be updated. The other major home project is to lay Pergo in my study - it's the only room of the house to escape the recent reflooring - and Wendy is not going to let it go undone. We'll be buying the materials next week, and will probably lay the new floor on Friday.

* * *

As I've been updating my web site, I've been using a variety of browsers to look at the new code (HTML4/CSS2, as generated by PHP3) to see how the different browsers render it. The list I've used so far is:

  • Netscape 4.x
  • Mozilla M17
  • Mozilla M18
  • Netscape 6.0
  • Internet Explorer 4.5
  • Internet Explorer 5.x
  • Opera 4.0 Beta
  • Lynx 2.8.2
All of the above, except for the IE browsers, I run under linux. I test my pages, both my HTML and my CSS, against the validators run by the W3C, so I know that both my HTML and my style sheets are legal, and should produce similar results, at least among the more recent browsers. Here are some things I have learned about each browser:

Netscape 4: It's not surprising that this venerable old browser does the worst layout job on my pages. But I suspect that, at least among the linux/unix crowd, it's still a widely used browser so it's good to know how my pages look in it. Not that Netscape 4 does a bad job, but it ignores some of the margin properties in the CSS, which tend to make its layout look very different than most of the other browsers. This layout can be corrected by using Netscape-specific attributes in the <body> tag, but then the HTML doesn't pass the W3C validator. I'd rather be standards-complient than pretty.

Mozilla: These three browsers (M17, M18, and Netscape 6) seem to do as good a job as any on my pages. Best as I can tell, layout is exactly as it should be and except for variations in font size, layout seems to be exactly as in the MSIE browsers (this is a good thing).

I like Netscape 6 very much; it seems to be the best yet of the Mozilla series. I would throw away my old Netscape 4 were it not for a very troubling problems. The most annoying is with printing; for some reason, the Mozilla print engine has real trouble laying out the page correctly when preparing PostScript for the printer. It seems to have the most trouble on pages that use both tables and graphics (in other words, most every page). I've printing several articles off the net in which the first page of the printed copy consists of nothing but a single banner ad, with the text following on subsequent pages. Why is layout for a printer so different than layout for the screen? Netscape 6 also seems to have some form-related problems with Advogato. Together these problems mean I won't be uninstalling Netscape 4 any time soon.

Internet Explorer: I'm no fan of Microsoft, but I have to say that its MSIE browsers are some of the best around. Both 4.x and 5.x seem to be fast and easy to use (if not exactly stable). I had heard that one or the other of these browsers had "broken" CSS support, but I haven't seen any sign of breakage. Both MSIE browsers render my pages exactly right so far as I can tell.

Opera 4.0 Beta: I probably wouldn't be testing with Opera except that I had heard such good things about it, so when a new beta version was recently announced on Slashdot or Freshmeat, I downloaded a copy. What a huge disappointment! It doesn't handle my CSS correctly, specifically in margin values and fonts. I specified my font family as "helvetica, ariel, sans-serif" which pretty much covers all worlds, but Opera insists on rendering my pages in a serif font, probably Times.

I also don't like its cluttered UI (all the browser makers need to learn that sometimes less is more). I especially loathe its windowing system in which documents float within a virtual desktop internal to Opera, in much the same way that documents float around within a Microsoft product like Word. Note to Opera: the application shouldn't be doing window managament - that's the Window Manager's job.

Needless to say, I'll be uninstalling my copy of Opera's browser the minute its 30-day eval license expires

Lynx: Good old depenable lynx. I don't use it on a day-to-day basis, but it somehow makes me feel good to know it's out there, still alive and healty and being kept up to date. My pages won't look beautiful in lynx, but they will at least be usable.

- = -
7 Dec 2000 (updated 7 Dec 2000 at 16:49 UTC) »

Finally! It looks like I may have fixed the emulator so that it will correctly run the OI29 software, in particular the GPCF stuff available through the 70-series SPEC pages. SPEC 71 is the one that was causing the most trouble, but it now appears to run correctly.

We found the problem yesterday, with the help of Roscoe and Paul from Flight Software. When we found the problem, though, it was late in the day so I left the fix for this morning. The fix turned out to be related to my earlier "fix", in which I realized that the intermediate addresses for the indirect addressing mode need to be expanded from 16 bits to 19 bits just like the final addresses are expanded.

When I added the code to expand these intermediate addresses, I made a real dumb mistake: I casted the 19-bit expanded address back down to an unsigned short, thus throwing away 3 bits of address. D'oh! Anyway, SPEC 71 no longer hoses the emulation, and I'm going to look at other places we expand address to see if I have any other address-truncation problems.

7 Dec 2000 (updated 7 Dec 2000 at 16:49 UTC) »

Spent the last couple of days tracking down a bug in the emulator; today I even had a couple of flight software guys helping me out. Their insight was invaluable. Without knowing how the low-level I/O routines work, I never would have figured it out. The problem turns out to be with the same addressing mode as the first I fixed. One of the AP101/S addressing modes with indexed, indirect, and its own flowchart to show how it works. This mode is so complicated that I might never get it completely right; maybe when we get the microcode listings I'll be able to do better.

5 Dec 2000 (updated 5 Dec 2000 at 09:51 UTC) »

Note to jules, who observed that Solaris users seem to dislike bash because it's not installed by default:

I discovered, much to my surprise, that bash is installed by default on Solaris 2.8. I was mucking around with my PATH the other day, and I took all the GNU stuff out (why, I don't remember), thinking that at my next login my shell would fall back to csh. But it didn't. I then discovered that bash resides in /usr/bin/bash. This was on a Sparc Ultra 10, right out of the box, default OS install, and still had that "new computer" smell.

Once I worked with a fellow who would have used bash as his shell, but the OS, via chsh(1), wouldn't allow it as a logon shell. He was a sharp guy, but he didn't try very hard to solve this one. It's pretty easy to make bash your default shell even on an uncooperative OS like Solaris using a bit of script like the following in your login script:

  export SHELL=/usr/local/bin/bash
  if [ -x $SHELL ]; then
    exec env SHELL=$SHELL $SHELL -login
The "env" in there is hanging around from when I used this snippet with csh. I changed the "if" syntax, but left the env. In ksh, I guess this would be simpler as "SHELL=$SHELL exec $SHELL -login".

I digress. To get back to the point, bash is available on newer Sun systems. Don't remember about less, but I do seem to remember gzip being on my new sun too. Even if bash weren't installed by default, what's the problem with building it? I've never had a problem with bash in six or seven years of use; "./configure; make" has always worked just fine for me.


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