Walt's boardset.

[Terry Fox]

I do hope this is the end of all this, so I can get back to ignoring MY projects.  No warranty expressed or implied.

After the call, dinner, etc... I looked at the boards again.  I set all the switches on the 2SIOJP(?) to match Walt's larger picture... no luck no boot.

So I looked at the FDC+ board switches more carefully and compared them to Walt's FDC+ picture.  Look the same... oh wait a minute,  It's hard to see from Walt's pix, but it looks like the EPROM address A11 is questionable, but it's up on the actual board.  AHA!  The switch (binary) description below Walt's pix says it should be opposite of how I have the board setup.

Wait a minute!  The EPROM enable switch on the FDC+ is turned OFF, so the EPROM address switches shouldn't matter.  BUT THEY DO.  As soon as I flip the EPROM A11 switch to the opposite direction, everything starts working.

AMON signs on and I can now hit the ? and get a dump of commands.  DU works.

Happy happy joy joy.

But why should an EPROM address switch affect anything if the EPROM itself is disabled?

I DON'T CARE!  I'M DONE!!!
Terry out

[Walt Perko]

Hi, 

 

I think I'm happy!   

 

Yeah, isn't it funny how the manuals work compared to the real world?  

 

And that's why I took photos of the two boards and typed the settings below to help people get up 'n running without needing to go through all the emails back 'n forth with Martin and Mike when I couldn't get things working back in 2023.   

 

 

.

[Walt Perko]

Hi, 

For the future readers ... this is the page I have online that has the two photos and settings to make life easier:  https://www.brainless.org/Altair/Altair8800c/index.html

.

[Terry Fox]

Actually, I'm still a little confused about the EPROM ENABLE switch.  It seems to be the opposite of the schematics. My switch is down (EPROM OFF?) in order for AMON on the other board to load.  I will look more into this tomorrow.

(my head hurts)

Walt, in the future you might consider taking the pictures at more of a vertical angle, as it's hard to determine the switch positions with the head-on shots. The shadows make it confusing.

[Patrick Linstruth]

The FDC+ provides RAM up to the ROM start address. This is true whether or not the ROM is enabled. By changing A11, you changed the FDC+ top of RAM. When using only the FDC+, RAM and ROM can never overlap. When external RAM/ROM is added, this protection goes away.

I went around and around with this before. I came to the conclusion if a system has an FDC+, 2SIOJP, and front panel, disable everything on the 2SIOJP and use Altmon on the FDC+. Why use ROM on a serial card when it’s already integrated into the FDC+.

Altmon is far less complicated and occupies less space. It also gives feedback when loading hex files, which is very helpful to know that it’s actually working. Most people just use “B”, “D”, “H”, and “G”, don’t need support for 6 different serial ports, don’t boot from hard disk or cassette, don’t need a terminal emulator, don’t use a teletype, don’t load binary files, don’t dump hex files, and don’t read the manuals (which is an absolute necessity for 2SIOJP and Amon). If Amon is really needed, burn the 2SIOJP ROM on the FDC+.

If the user tends to need assistance from others, most everyone with an FDC+ uses Altmon and is familiar with it.

By disabling all the 2SIOJP features, it can typically be ruled out as the source of problems. It is also one of the most complicated boards to configure and changes from revision to revision. The documentation is as incomprehensible as the board itself.

Pictures are only good if the exact configuration is described. It is better to understand what the jumpers are doing in addition to pictures. Give a man fish, feed him for a day. Teach a man to fish, he’s fed for life. FDC+ plus book is a great example. Mike explains how to set up 5.25” drives and what the different jumpers do. He then provides pictures.

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[Terry Fox]

I understand Patrick, thanks.  If Walt is willing to use Altmon instead of AMON, I can set his boards up for Altmon.  It's his boardset, and he has said he wants AMON, so that's what I'm doing.

Walt, what do you think?

Terry