Calling on Color Classic owners who own a TechStep

[JDW]

I'm not getting any replies in the TechStep recreation thread, so I decided to make this a new post.

If you own a Color Classic with the stock motherboard and also have a TechStep along with the required Vol.4 Cartridge for testing the stock CC M.B., I've love to hear if you are able to perform all the tests.

I have the 84V 640x480 screen mod, which allows me to use the stock CC motherboard. However, I found I was not able to test my stock motherboard using a Vol.4 TechStep cartridge recreation. However, I also have the LC520 board and was able to use the same Vol.4 cartridge to diagnose that motherboard just fine, so I'm guessing it's probably not a bug in the cartridge recreation. It very well could be the existence of the 640x480 screen mod; but in order to find out, I need to call upon my fellow Color Classic and TechStep owners to do further testing.

Some of you may have the VGA mod while others may use the CC stock resolution, and it would be great to hear from all of you.

If other 84V 640x480 mod users can't get their stock M.B. to be diagnosed by the TechStep either, and someone with the stock resolution comes along saying they can use their TechStep to diagnose it, then such offers hard evidence that the TechStep will ONLY diagnose the stock CC motherboard if the resolution is also set to stock.

Thanks!

Oh, and if you want to know more about the 84V 13" High Resolution Mod, I just released a video about that here:

 

[SuperSVGA]

Mine works fine on a stock CC with no mods. All tests pass except for sound on my board, though maybe I just have something broken there.

Are you able to test to make sure serial is working properly, or check the -5V somehow? It did look like the TechStep was putting it into test manager fine, but wasn't able to reach it over serial maybe.

 

[JDW]

Thank you for very much testing and replying back. I really appreciate it! I'm overjoyed, in fact!

I wired everything in the same way I wired the LC520 motherboard, which is meaningful since the ports on the stock CC M.B. and the 520 board are the same, yet the 520 worked with the TechStep's Test Mode while the CC did not.

If it were serial port related, that still doesn't explain why accessing Test Mode via ADB and also SCSI didn't work in my case. If you skip to 40:57 in my video, you will see it says "could not enter TstMd via ADB." It then presents me with the option to access Test Mode via SCSI. I show myself attempting that, but it then says both methods of accessing Test Mode failed...

I know ADB works fine because when I remove the TechStep and setup the machine normally with the stock CC M.B., I can connect an Apple IIgs keyboard to one ADB port and an Apple mouse to the other, and both mouse and keyboard work fine.

You said that with the stock CC screen resolution your TechStep and cartridge Vol.4. works fine to enter Test Mode, so that seems to give strong evidence to support my theory that the VGA modded resolution of 640x480 must somehow be interfering with the Vol.4 cartridge diagnosing the stock motherboard.

 

[SuperSVGA]

I believe both the ADB and SCSI entry methods are just putting the computer into test manager mode, same way you would do by hitting the interrupt switch on machines that have it. ADB is likely just sending the interrupt key combo (i.e. Command + Power) on machines that support it, and the SCSI method is just a fake disk to jump to the test manager. Once in the test manager, all the communication is done over serial.

All of the actual running of tests is just plain serial commands. You could even do it with another computer, just by getting the machine to the sad Mac screen and using serial terminal software you can manually issue commands and run tests.

 

[JDW]

But here's the thing. I have two Serial Loopback Plugs, and Snooper 2.0 completes testing of the serial ports multiple times without error:

I tested that just now with the stock CC motherboard and of course 640x480 resolution via the 84v screen mod.

 

[robin-fo]

stock CC M.B. and the 520 board are the same

Is it? You mean stock CCII?

The stock CC is more like a Classic II or LC II

 

[JDW]

Is it? You mean stock CCII?

I wrote this in my earlier post...

since the ports on the stock CC M.B. and the 520 board are the same

Meaning, two ADB ports, in comparison to the LC575 board which has only one. I was using the term "the same" only to refer to the ports being similar.

The stock CC is more like a Classic II or LC II

Indeed, and we see that in the April 1993 issue of MacUser magazine (which I subscribed to back in the day, and which later was rolled into Macworld, the digital version I still subscribe to today)...

And of course the same painful limitation...

And performance...

But how does all that factual knowledge about the similarity to an LCII help explain why my genuine Apple TechStep with a Vol.4 cartridge recreation (which tests both the LC520 and CC motherboards) could diagnose the LC520 just fine, but could not initiate Test Mode when used with the CC motherboard?

@SuperSVGA said this:
"Mine works fine on a stock CC with no mods. All tests pass except for sound on my board"

He did not say if he had the genuine Apple TechStep and the genuine Apple Vol.4 cartridge. I only know that a "stock CC with no mods" means the "stock resolution." And that is where our two machines differ in that I have the 84V 13" High Resolution mod installed, which allows 640x80 resolution and compatibility with the stock CC motherboard (something that the 68.4V VGA mod does not offer).

In other words, what is known is a difference in screen resolution between myself and SuperSVGA. If he used a recreation cartridge, then that would make our TechStep testing the same, leaving only the resolution difference the possible reason why my test failed.

Of course, someone reading this thread could come along and say they are able to get it to work with a genuine Apple cartridge, which would mean maybe there is an issue with the cartridge recreation and resolution would then be irrelevant. But that is really why I created this thread, to answer the simple question about why my own TechStep testing failed when attached to the stock CC motherboard.

So if anyone has something new to add, that extra testing info would be welcomed. For now, I am ascribing the reason for my testing failure to be VGA resolution.

 

[JDW]

By the way, this is a teensy tiny bit off-topic, but since I started this thread it's no big deal...

I never liked the look of the Color Classic back in the day, and it wasn't only me. The April 1993 issue of Macworld had this to say...

But like Tim Warner said in the end, I found that after acquiring and actually using one for a while, the look of the machine "grows on you." Especially so if you use it normally, which means you are gazing at the front of the machine exclusively.

I wanted to mention this because whenever we ponder topics related to the Color Classic, you can't help but consider how the machine looks. And "looks" are a big part of any meaningful experience with an Apple product, new or old.

 

[ClassicHasClass]

I believe both the ADB and SCSI entry methods are just putting the computer into test manager mode, same way you would do by hitting the interrupt switch on machines that have it. ADB is likely just sending the interrupt key combo (i.e. Command + Power) on machines that support it, and the SCSI method is just a fake disk to jump to the test manager. Once in the test manager, all the communication is done over serial.

All of the actual running of tests is just plain serial commands. You could even do it with another computer, just by getting the machine to the sad Mac screen and using serial terminal software you can manually issue commands and run tests.

Funny you should mention - I MITMed a number of transactions between my TechStep and various machines here in the shop and have traces of the communication. However, a lot of it is just uploading code to the machine and seeing what the result is, which makes forming a "unified theory" slow going.

If the UUT doesn't reply to a command, the TechStep may conclude the device isn't responding. However, I have an SE/30 that doesn't respond to *V (version) but otherwise responds to other commands. I'd open a serial link and see if that's the case with this one (9600 8N2).

Some hardware tests will cause the serial link to be lost, but this may be an artifact of how I'm monitoring the serial ports.

 

[SuperSVGA]

I did use an original TechStep, but I'm not sure where my original Vol. 4 cartridge is so I just built a new one yesterday. There shouldn't be much difference between the cartridges though, there isn't much going on in there.

It is very odd though, making changes to display resolution shouldn't have any effect on the TechStep's ability to communicate. Even the TechStep's display tests just write directly to VRAM, so worst case they just won't look correct.

However, I have an SE/30 that doesn't respond to *V (version) but otherwise responds to other commands.

The SE/30 ROM does not support the Version command, and also does not have the entire non-critical test suite that later ROMs have. You would need a IIci or IIfx ROM to get the non-critical tests, and I believe the IIsi ROM is where the Version command was added.

 

[dougg3]

For what it's worth, on the ADB side, bbraun discovered back in the day that the TechStep sends a special ADB command on machines with an Egret/Cuda to enter the test manager, which can't be sent with a normal keyboard:

https://web.archive.org/web/20161206213818/https://mac68k.info/wiki/display/mac68k/Diagnostic+Mode#DiagnosticMode-ADB

On machines with the Egret ADB transceiver (>= IIsi?), diagnostic mode can be entered via ADB. Unfortunately, this can't be done with a normal keyboard, and requires a special device to send the proper code.

 

[robin-fo]

since the ports on the stock CC M.B. and the 520 board are the same

I must have skipped the first part of the sentence.. Sorry, please apologize

I have a stock CC and a TechStep replica. At first, it didn‘t want to enter test mode, but I had just one ADB cable attached. When I tried with two ADB cables, it worked with no issues. All logic tests passed.

 

[JDW]

I have a stock CC and a TechStep replica. At first, it didn‘t want to enter test mode, but I had just one ADB cable attached. When I tried with two ADB cables, it worked with no issues. All logic tests passed.

Thank you very much for testing and reporting back!

So, we now have 2 people thus far with the stock resolution and with a TechStep replica cartridge Vol.4 (whether a removal one or one inside the memory of the Replica TechStep shouldn’t matter), and both gentlemen can diagnose the stock CC MB just fine when using two ADB cables.

I used all the cables with with VGA resolution and couldn’t enter Test Mode.

So if any other TechStep owner with cartridge Vol.4 can do a test on an 84V 640x480 resolution modded CC with stock CC motherboard, that would be the definitive test. Because if they cannot enter Test Mode either, that basically offer us all the proof required to show that somehow the resolution difference is the only thing preventing the TechStep from entering Test Mode.