Repairing a Convergent Technologies Miniframe, Part 2
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- Опубліковано 15 лип 2024
- Part one left the miniframe in dire shape, unable to boot or do anything more that blink some diagnostic LEDs. In this video, I use a diagnostic ROM to examine memory and set breakpoints in the boot loaded. I replace a whole bunch of 74XX logic, then I get out my logic analyzer and troubleshoot the problem. By replacing some 74LS461 ICs and replacing a PAL, I get it to the point where it boots, but still experiences occasional memory errors and core dumps. I then transition to playing with a second miniframe, one that works quite a bit, as well as a Convergent terminal that connects to the miniframe. I succeed at hangman, but fall into a pit while hunting the wumpus. For more electronics videos, see www.smbaker.com/
- Наука та технологія
Mannnn, I love old Unix stuff. 🍿
Ooh, channel without a blaring intro theme, autie likes 👍
Wow. Found this vid on a search for photos of the AWS terminal. What a neat little product that was. Motorola was reselling Convergent and I had Mins in my lab there, built a graphics frame buffer for it that sat on the memory add-in stack. With a hardware sprite, woo-hoo! They came with plated media hard drives, when that tech was still pretty half-baked. Once those were replaced it was a rockin little machine and my intro to unix.
The first thing I wanted to know was how did they get a 10 MHz 68K to run no-wait with 120 ns DRAM. The timing didn't work if you waited for the address strobe to start a RAS. But the address came out half a clock sooner. So they sacrificed half the physical address space (never would be needed), by using A23 low to start the RAS. Tricky!
I worked with SLIP on MiniFrame in the late 1980's when interfacing a hotel MiniFrame system in Honolulu to an offsite Motorola Unix computer. There was an issue with the mark/space signaling between the machines for SLIP and I was able to get the SLIPD source and recompile it with a fix to resolve the issue.
I worked with CTIX many years ago (when I was very young and starting to work). It was for a bank that used them for teller terminals.
That Discord notification chirp after "Maybe we can hunt the wumpus!" actually got me, nice job. Excellent video, I love seeing earlier systems like this being brought back up and running. Is there any chance of cloning/recreating the PAL you'd borrowed from the working min, so that both machines have working drive controllers?
There is a min service manual with PAL listings in it, so I think there's a good chance I can clone that particular PAL. Unfortunately, not all the PALs in the broken min are identical to the ones in the service manual (or to the good min), and the schematics are not the same either. Convergent must have had a hardware revision in mid-1984. I will try to replace the PAL with an ATF22V10 at some point.
Yes, me too!!!!
I admire your patience and determination. That some real esoteric stuff.
23:15 SLIP was an early quick-and-dirty layer-2 implementation for transmitting TCP/IP packets over RS-232 lines. It was common in the early days of dialup Internet, but was soon replaced by the more elaborate and more general PPP. PPP was sufficiently versatile to be adaptable to other serial transports, like ATM, and even Ethernet used as a point-to-point link.
Great staff saving! You can find Logic Analyzers like HP 1650A with over 100 inputs for reasonable prices.
Gota tell you, shot-gunning IC's on a complex board is the fastest way I know to kill any chance of getting the, usually, single bad IC out. Not only do you risk putting a non-compatible IC in which is a later model of the same IC but is now faster and not 100% backwards companiable. Then there's the risk of installing an IC with a new problem, not to mention, destroying a lan(s) on the board, especially, on multilayer boards and then you'll never get the board going again.
I agree with using diags and your logic analyzer but often I have my best results with a decent Logic probe and pulser combo; though I do have a decent Logic. Analyzer and use it often. I have a discontinued Digiview 3100A LA which is outstanding. They have ewer models now but Saleae is very good as well. Digiview has some greet tutorials on YT which are worth a watch.
I also use the HP 545, 546 and 547 logic kit. Thats probe, pulser a the OUTSTANDING HP 547 current tracing probe. I have found many problems with this probe as the current rises at a bad gate. These probes are long out of production but are highly coveted by techs and engineers alike. Expect a complete set to set you back of $600 but to me, worth every penny.
Thermal cameras are much cheaper now and are really good if you have a known good board to look at, at the same time. Of course, this is not always possible. The IR camera will show hot spots quickly. A less effective but even cheaper is a Temp probe. I have the Fluke but you can get a cheap equivalent at Harbor Freight for peanuts.
. I use to use the back of a finger and quickly rake it across RAM if I thought one was bad. Also effective on many IC's and good for an occasional blister.
Good luck
Wonderful
Amazing Work! Again!!!
No
@@thenewBH Awesome!
22:44 my Wall-MiniFrame DOES indeed have an Ethernet board installed, so perhaps I should repeat your test on that machine? Be cool to see the results. Yes!
glad you have one of the Ethernet boards! I think I recall seeing the Ethernet MAC address stored in the VHB of the min disk image (unlike on the UNIX PC)
19:48 This actually blows my mind. The Min is already running and supposedly booted when you flip the switch on this thing, and so now the TERMINAL has to boot? Before now, I was considered knowledgeable with vintage Convergent stuff...but you're totally blowing my mind on this one. And I even HAVE one of these terminals that I have not yet worked with yet (so that could be why...)
And note how the terminal boot-up status operates VERY similarly to AWS and NGEN boot-up? Interesting
As far as I can tell, the image that boots on the terminal is located at /usr/lib/iv/ws100.422 -- I think it's similar to a "cluster only" (no disk) AWS. The naming on the file is interesting, "WS100" -- as the IWS model numbers are WS-110 and WS-120. There is also a /usr/lib/iv/ws200.422 file, which is similar to the AWS model numbers and may be to boot a cluster only AWS machine ("cluster station").
Cool!! Though I don't know this exact OS, just my gut feeling from UNIX experience, the problem near the end (save etc) was because of non-cleanly unmounted filesystem ("dirty") could be only mounted as read-only (should be fsck'd and remounted r/w then), thus the lots of errors during boot as well, that daemons could not create their things, etc.
IGota tell you, shot-gunning IC's on a complex board is the fastest way I know to kill any chance of getting the, usually, single bad IC out. Not only do you risk putting a non-compatible IC in which is a later model of the same IC but is now faster and not 100% backwards companiable. Then there's the risk of installing an IC with a new problem, not to mention, destroying a lan(s) on the board, especially, on multilayer boards and then you'll never get the board going again.
I agree with using diags and your logic analyzer but often I have my best results with a decent Logic probe and pulser combo. Though I do have a decent Logic. Ana and use it often. I have a discontinued Digiview 3100A LA which is outstanding; they have newer models now They don;t advertise as much as others but they are well known and respected in the industry. Saleae is very good as well.
Digiview has some greet tutorials on YT which are worth a watch.
I also use the HP 545, 546 and 547 logic kit. Thats probe, pulser a the OUTSTANDING HP 547 current tracing probe. I have found many problems with this probe as the current rises at a bad gate.
These probes are long out of production but are highly coveted by techs and engineers alike. Expect a complete set to set you back of $600 but to me, worth every penny.
Thermal cameras are much cheaper now and are really good if you have a known good board to look at, at the same time. Of course, this is not always possible. The IR camera will show hot spots quickly. A less effective but even cheaper is a Temp probe. I have the Fluke but you can get a cheap equivalent at Harbor Freight for peanuts.
. I use to use the back of a finger and quickly rake it across RAM if I thought one was bad. Also effective on many IC's and good for an occasional blister.
Good luck
are there any reproductions of mini frames?
I'm pretty sure there aren't.
interesting
Did you ever come across Arcnet networked devices?
The closest I had was a Lantastic back in the day. It clearly predated Ethernet, but I'm not sure if it was Arcnet or a proprietary protocol.
RetroBytes has done a video on Arcnet.