This has really been a great series to read. Does anybody know where this will live when they are done restoring it?
Restoring YC's Xerox Alto day 8: it boots
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Re: Restoring YC's Xerox Alto day 8: it boots
#52I'm trying to read the article on an iphone but every time I zoom out to see the full width article I get bounced over to an article about toothbrushes?! For the better part of a minute I was wondering if they had monkey-patched the disk controller with an electronic toothbrush?!
Geez, I thought it was because I'm using a beta of iOS. I figured apple had goofed something in the gesture recognition in this build. Glad you posted something, I was debating filing a bug.
Re: Restoring YC's Xerox Alto day 8: it boots
#53Earlier quoted context omitted.
We're building a FPGA-based disk emulator that we could connect to the Drive to rewrite the junk disk, but we don't have that ready yet. The Living Computer Museum could have rewritten our disk for us, but that would have required sending our disk to Seattle first so they just sent us a new disk. (The Living Computer Museum has been extremely helpful, so visit them if you're in the Seattle area!)
Their assistance was really shrewd; I've been to the CHM in Mountain View before, but had never heard of the LCM and probably would never have gone before this, but now I'm definitely going to go the next time I'm up in Seattle.
Yeah, I'm going to wrangle up some nerds and see if we can make a day of it.
Re: Restoring YC's Xerox Alto day 8: it boots
#54I love that the first boot screenshot at https://lh3.googleusercontent.com/-JB4VOj7FgnU/V-lCHIADrsI/A... says: Date and Time Unknown Oh, you poor sweet computer, if we told you the answer, it would blow your little mind.
The PC had no RTC, so DOS would ask you the date and time every time you booted it:
https://en.wikipedia.org/wiki/File:PC_DOS_1.10_screenshot.pn...
...and if you accepted the default, as many people at the time did, it would be 1980-01-01 00:00:00. DOS and the PC actually had no Y2K problem, storing the number of years since 1980 in a single byte --- which will overflow after 2235. It is notable that there is no year 2038 problem either.
I'm not sure what the Alto's RTC capabilities are. Hopefully a bit better than the PC's?
Re: Restoring YC's Xerox Alto day 8: it boots
#55This has really been a great series to read. Does anybody know where this will live when they are done restoring it?
It will probably be at the YCombinator office for a while but we haven't figured out a long-term plan. Any suggestions?
Re: Restoring YC's Xerox Alto day 8: it boots
#56The disk seek problem didn't mysteriously disappear. You need to bust out some some contact cleaner and clean those header strip connections, both sides.
Re: Restoring YC's Xerox Alto day 8: it boots
#57The living computer museum is an amazing place. Highly recommend visiting if you ever come to Seattle.
Re: Restoring YC's Xerox Alto day 8: it boots
#58Earlier quoted context omitted.
Probably out of fear that the signals might deteriorate with probes attached. But with a modern-ish logic-analyzer and the ancient original hardware (huge voltage swings, slow clock, very long busses), I doubt that the probes would make a discernible difference, would they?
Yes, you're right about the signals. The Alto has a 5.88 MHz clock which is very slow by modern standards, and the buses are a couple feet of wire-wrapped pins so the probes are unlikely to have any effect. I'm not sure modern-ish is the right word for the logic analyzer. It's a 1999 Agilent logic analyzer and I don't know how they managed to make it so slow. You can ftp a trace off it over Ethernet at the glacial sp…
Back in the old days, we saw crosstalk at at 4Mhz. I think circuits absent a pullup can be susceptible. But in general, I agree, you're more likely to break something removing and reinstalling the probes.
Which reminds me, one time back at my first job, the hardware guys were working on a new design, and it only worked with the logic analyzer probes attached to the CPU. They later discovered a missing connection between a pullup or pulldown resistor and the appropriate +Vcc or GND supply.
Re: Restoring YC's Xerox Alto day 8: it boots
#59Re: Restoring YC's Xerox Alto day 8: it boots
#60This series is the best thing on HN in a long time. As a software engineer by trade, I feel like I've been missing out not learning more about electrical engineering. The level of knowledge and skill involved in this restoration is downright awe-inspiring.
If you have the time and interest, get a broken 80s system and a cheap logic analyser. Try to fix it; I learnt most that way. Or get a working and a broken and first analyse the working and then the broken.