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  #11  
Old 10-15-2007, 01:27 AM
Geoff Harrison Geoff Harrison is offline
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Originally Posted by Grant Stockly View Post
Did you try 9600 or 19200?
I tried a maximum of 9600 and was losing characters due to the lack of handshaking. I'm going to order another Molex connector and pins and make a proper cable, but that's probably about a week away. I think you have mentioned before that Tera Term allows inter-character delays, so that should be another way to slow down the transmission to allow the Altair to keep up at 9600. However, the only configuration I have tested with my 2SIO card is 4800,8,n,1, no handshaking.
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Paul, make sure to change the jumpers on the 2SIO for 4800.
Good point
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  #12  
Old 10-15-2007, 04:05 AM
phe phe is offline
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Geoff, this is awesome information. Thanks a lot!

I've tried it several ways tonight without diving too deep to try to figure out what I am doing wrong. I can confirm it will not work at 9600 for me either, but it could be for an entirely different reason.

Rather than resetting my card to 4800, I've tried the intercharacter delay. I even tried 100ms, which makes the transmit rate very slow. I cannot tell if Basic is loaded into memory or not, all I can confirm is that I cannot get anything to display and that the low memory locations do indeed get changed.

A quick glance at the loader helps me see how it is set for 020/021. I'll use this to try to debug what is going on. Unfortunately I have to head out of town tomorrow for two weeks. What lousy timing!

Tell me about switches A11 and A10? I was surprised to see you put both on.

Paul
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  #13  
Old 10-15-2007, 04:44 AM
Geoff Harrison Geoff Harrison is offline
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Sorry to hear it didn't work. I'll try setting my 2SIO back to 9600 and setting the character delay to see whether I can get it to work that way.

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Unfortunately I have to head out of town tomorrow for two weeks. What lousy timing!

Tell me about switches A11 and A10? I was surprised to see you put both on.
No problem. It gives me more time to write up my more detailed description of what's going on with the boot loader. I'll post it in a day or two.

A11 tells the 2nd stage loader (what MITS calls the checksum loader) and Basic that the terminal is on a 2SIO, A10 tells them how many stop bits to use; up=1 stop bit, down=2 stop bits.
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  #14  
Old 10-15-2007, 07:20 AM
Grant Stockly Grant Stockly is offline
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Quote:
Originally Posted by Geoff Harrison View Post
I tried a maximum of 9600 and was losing characters due to the lack of handshaking. I'm going to order another Molex connector and pins and make a proper cable, but that's probably about a week away. I think you have mentioned before that Tera Term allows inter-character delays, so that should be another way to slow down the transmission to allow the Altair to keep up at 9600. However, the only configuration I have tested with my 2SIO card is 4800,8,n,1, no handshaking.
I forgot about that! I've used that to "type" in basic programs to the Altair. You WILL need a delay for line EVEN with 300bps!

There are two kinds of delays in terra term. Character and Line. Hyperterminal has the same thing. It is kind of annoying that these delays are not available for telnet connections, but that doesn't matter for us.

Click the "Setup" menu and select "Serial Port". Look for the "Transmit delay" frame at the bottom.

I think at 9600bps I used 5-20ms for character and 200-300ms per line.

There are ways to optimize speed based on the echo from the Altair, and I will try to perfect those methods later and release a special Altair basic transfer program. The Altair tokenizes basic lines after a LF. Not all basic lines take the same amount of time, and it seems as memory gets filled up it takes longer (what??? ). Any way...I myself would prefer to bootstrap basic at 9600bps with a delay than run at 4800bps all the time.
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  #15  
Old 10-15-2007, 07:23 AM
Grant Stockly Grant Stockly is offline
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Quote:
Originally Posted by Geoff Harrison View Post
A11 tells the 2nd stage loader (what MITS calls the checksum loader) and Basic that the terminal is on a 2SIO, A10 tells them how many stop bits to use; up=1 stop bit, down=2 stop bits.

And in the manual 1 and l are the same character. When I got my first Altair with disk drives the instructions were to raise switch "A11", which looked like All to me.

It took a while to figure that one out.
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  #16  
Old 10-15-2007, 07:27 AM
Grant Stockly Grant Stockly is offline
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Quote:
Originally Posted by phe View Post
Rather than resetting my card to 4800, I've tried the intercharacter delay. I even tried 100ms, which makes the transmit rate very slow. I cannot tell if Basic is loaded into memory or not, all I can confirm is that I cannot get anything to display and that the low memory locations do indeed get changed.

A quick glance at the loader helps me see how it is set for 020/021. I'll use this to try to debug what is going on. Unfortunately I have to head out of town tomorrow for two weeks. What lousy timing!
Did you see ANY blinking in the lights in any of the tests? Your card is set for port 020/021, right? Not like the one in the picture I sent you? I had mine setup for CP/M which required the 2SIO be at port 0/1.

Did you have both the 4k and 1k memory card installed? Did you change the jumper setting on the 1k memory card? For the initial tests don't have the 1k memory card installed.
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  #17  
Old 10-15-2007, 07:30 AM
Grant Stockly Grant Stockly is offline
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Originally Posted by Geoff Harrison View Post
No problem. It gives me more time to write up my more detailed description of what's going on with the boot loader. I'll post it in a day or two.

I have been putting off shooting mini training videos for the Kenbak. When I'm doing that maybe I can have a basic boot demo with the Altair. Just to make sure all of the switches/etc are done in the right order.

Paul hasn't ever used sense switches before. (I think) In fact, we should probably write a small program for him that tests the sense switch function. How about a program that reads the sense switches and transmits that value continuously to the serial port. We can use that along with "Serial Device Tester" from Hack Consulting to make sure his sense switches are all functioning.
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  #18  
Old 10-15-2007, 01:33 PM
phe phe is offline
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Quote:
Originally Posted by Grant Stockly View Post
Did you see ANY blinking in the lights in any of the tests?.
Blinking? No. I looked for that. But I saw some dim lights.
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Originally Posted by Grant Stockly View Post
Your card is set for port 020/021, right? Not like the one in the picture I sent you? I had mine setup for CP/M which required the 2SIO be at port 0/1..
Yes, it is set to 020/021. Remember that the echo is working, which is using 020/021.
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Originally Posted by Grant Stockly View Post
Did you have both the 4k and 1k memory card installed? Did you change the jumper setting on the 1k memory card? For the initial tests don't have the 1k memory card installed.
I have both installed.

That's about it. I'm headed out of town now. I'll be able to check this board again during my trip, but won't have the Altair with me

Paul
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  #19  
Old 10-16-2007, 03:08 AM
Geoff Harrison Geoff Harrison is offline
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I have posted a preliminary version of my discussion about the bootloading process here. I'll try to tidy it up a little over the next few days and add more troubleshooting hints when I think of them.

It goes into more detail than any sane person could want to know about booting Altairs, I hope it's not to dull to read.

Unfortunately, I can't do any more testing with windows for a while. My file server went down hard today and I had to scavenge my windows machine to get it running again. I'll do more testing when I get a new motherboard for it.
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  #20  
Old 10-21-2007, 12:05 AM
Geoff Harrison Geoff Harrison is offline
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Originally Posted by Geoff Harrison View Post
I tried a maximum of 9600 and was losing characters due to the lack of handshaking.
Just a follow up to my 4800 baud maximum speed issue. I have rewired the connection between my 2SIO board and the rear RS232 connector and I can run reliably at 9600 now. It had nothing to do with handshaking, the boot loaders don't even try to throttle the input anyway. I can only assume there was a bad connection with the old cable, which was one that was originally in my 8800b so it was probably about 30 years old.

Anyway, 9600 works fine and is definitely preferable to 4800. I did have to make sure that the DB25 pins 4, 5, & 8 were tied together to keep the 2SIO and my linux laptop happy. I don't know whether windows would be any different, I don't see why it would. I'll find out when I get a new motherboard for my windows machine next week.
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