The video of the Alto booting is now available: https://news.ycombinator.com/item?id=12590137
Restoring YC's Xerox Alto day 8: it boots
91–99 of 99 posts
Re: Restoring YC's Xerox Alto day 8: it boots
#92Earlier quoted context omitted.
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…
Have you tried a different ethernet switch connected to the logic analyzer ? One cause of really slow transfers is one end getting the full/half duplex negotiation wrong.
That's a brilliant idea, I almost forgot about this. When I installed networking gear in the 90s, common knowledge/best practice was to always fix duplex/link-speed on fixed installed gear (routers/switches) because they frequently messed up autonegotiation.
Try a managed switch where you can choose 10/100, Full/Half and see statistics. Also try to get a "netstat/ifstat" like display on the logic analyzer to see bad packets/collisions/...
Re: Restoring YC's Xerox Alto day 8: it boots
#93Earlier quoted context omitted.
Yeah, yeah, get me the EGA card/memory update that includes the Dallas real time clock!
It's always weird hardware combinations like that that makes me look batch at the early PC era and wonder what drove some of those decisions. Like all the sound cards that included a free extra ide controller for running CD-ROMs, you couldn't boot off them most of time but it meant you could play games and music CDs, assuming you had the correct extra audio cable to connect the two (many systems couldn't read the raw…
All of my joystick ports were on sound cards. As for the IDE controller, a lot of computers in the late 80s and early 90s only had one IDE channel, and it was pretty common to buy a sound card and CD-ROM at the same time (I remember the first ones my family bought were bundled in a "multimedia upgrade kit"). If you already had two hard drives, you were short on options, except that the sound card provided a solution.
Re: Restoring YC's Xerox Alto day 8: it boots
#94I 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.
I happened to come across the Alto's time handling code [1] while looking for something else. The Alto counts seconds since Jan 1, 1901 and the time can run until 2036 since it uses a 32-bit value. (Unix time in comparison runs from 1970 to 2038; it runs half as long because it loses a bit by using a signed value.) The point of this is the Alto can handle dates until 2036, but will run into problems two years before…
32 bit unsigned seconds spanning 1901-2036 is the same representation as NTP.
Re: Restoring YC's Xerox Alto day 8: it boots
#95<
Re: Restoring YC's Xerox Alto day 8: it boots
#96Earlier quoted context omitted.
No, flash is called flash because of the speed, relative to other programmable memories that can be erased.
"Flash memory (both NOR and NAND types) was invented by Fujio Masuoka while working for Toshiba circa 1980. According to Toshiba, the name "flash" was suggested by Masuoka's colleague, Shōji Ariizumi, because the erasure process of the memory contents reminded him of the flash of a camera." https://en.wikipedia.org/wiki/Flash_memory#History
That's really weird and not what I remember being written back in the day when flash was invented. There is no 'flash' (optical erase process using UV) to go with flash memory, the erasure is electrical.
The 'eWeek' article that that paragraph was sourced from doesn't contain any explanation of why the association between the two was made, maybe early 'flash' memory did have an optical erase process?
Here is the quora link for the question why 'flash' is called 'flash':
https://www.quora.com/Why-is-flash-memory-called-so
Which is apparently sourced from a book about FPGA's, not directly accessible but roughly what I remember being written about flash at the time it came out.
http://www.linfo.org/flash_memory.html
Gives a similar definition.
Optically erasable memories existed but I'm not aware of any that have erasure times Eeproms (electrically erasable eproms) already existed well before 'flash' came along and flash is an improvement in speed on those, not a re-vamp of the optically erasable eproms.
It would be interesting to contact Toshiba to see if that quote from the inventor of flash memory can be substantiated and how to determine what the association with photography is if it does not refer to optical erasure.
Re: Restoring YC's Xerox Alto day 8: it boots
#97The disk seek problem didn't mysteriously disappear. You need to bust out some some contact cleaner and clean those header strip connections, both sides.
Yes it is mysterious.
Was that drive known good then?
Also what is the track sense mechanism?
Optical shaft encoder? Could have been just a bunch of dust.
Also a lot of drives used a Hall sensor or even an opto-coupler with a slot to detect track zero. First thing was to calibrate the head with a track zero seek.
Another thing. Those flat ribbon cables are prone to a lot of RFI over long distances, especially when you have them hanging around on the bench. Notice some of the other ribbon cables are twisted pair. A lot better!
I've wire wrapped my own disk controllers back in the early 80's. This series is serious nostalgia! Curious to know what the final problem will end up being diagnosed as.
The smell of old hardware like that is literally burned in my brain!
Re: Restoring YC's Xerox Alto day 8: it boots
#98What were the CPU/ ISA used in the Alto?
To the programmer, the Alto's instruction set is the same as the 16-bit Data General Nova minicomputer, with the addition of a few crazy instructions such as "copy character bitmap from font file to screen". The Alto's CPU is built from a whole pile of TTL chips on three boards. The Alto's arithmetic-logic unit, like many computers of that era, uses 74181 ALU chips. The CPU runs a crazy multitasking microcode, with o…
Oh man I've used a Nova. Never come close to using an Alto.
You guys are rocking it. Really enjoying dropping by and seeing how you are doing.
Really cool!
Re: Restoring YC's Xerox Alto day 8: it boots
#99What were the CPU/ ISA used in the Alto?
To the programmer, the Alto's instruction set is the same as the 16-bit Data General Nova minicomputer, with the addition of a few crazy instructions such as "copy character bitmap from font file to screen". The Alto's CPU is built from a whole pile of TTL chips on three boards. The Alto's arithmetic-logic unit, like many computers of that era, uses 74181 ALU chips. The CPU runs a crazy multitasking microcode, with o…
Oh man I've used a Nova. Never come close to using an Alto.
You guys are rocking it. Really enjoying dropping by and seeing how you are doing.
Really cool!