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RE: [N8VEM-S100:5129] JAIR 8080 Board- It's alive!

Hi Jeff,

Thanks.  I tend to use ? to get help screens, or sometimes, just hit enter.

I don't know the .DSK format, if it's Dave Dunfield's format, then it's not the same, he stores information about the file in the start of the file, the rest is all data.  I'm not so sophisticated, the file I'm looking for is ALL DATA, good, bad or ugly.  This makes my math a little easier when looking for "sector 0" of the virtual drive (aka file), I just read the first 128 bytes of that file. 

Great idea to test some of your other RAM boards.  All the old S-100 RAM boards I have were all bad!  That set me back 2 months of head scratching until I used one of Andrew's boards to build a new memory board.


Date: Mon, 1 Sep 2014 21:39:26 -0400
From: jgal...@optonline.net
Subject: Re: [N8VEM-S100:5129] JAIR 8080 Board- It's alive!
To: n8vem...@googlegroups.com

Hi Josh,
  Thanks for answering my questions as I know you are busy getting ready for VCF-MW (along with everyday responsibilities).  I am currently using the 8080 board in my test bench setup which consists of an N8VEM S-100 backplane, and an IMSAI front panel.  The mask and plexiglass were damaged so I removed them and am using the front panel bare until I restore the machine it is going in.  I hope to take some photos tomorrow as you had said a few weeks ago that pictures would be nice. 
  I wound up using a 2GB Transcend Digital card formatted as FAT16.  Thank you for describing the boot process in detail.  I may try loading a CP/M image from another source like an emulator since the boot ROM will not load the bios off the disk.  One question I can think of is that most the the emulators I have seen use the .DSK format for images while you are using .BIN images.  Do you know what the differences are between the 2 formats?
  Thanks for providing some syntax for the XMODEM & RAM test commands.  I now realize that I should have looked more closely at your monitor listing as it was all described there.  I will try to use the XMODEM command to transfer some files and see how I make out.  BTW, I do like how you make use of the front panel output port LED's to act at a progress indicator. Now I can also use the RAM test to test some external boards I have by disabling blocks of onboard memory and addressing the external boards in that address space.. Great! Thanks for all your help!

On 9/1/2014 7:42 PM, Crusty OMO wrote:

Excellent! I'm really happy to hear your enjoyment in building this card.  I'm curious, what front panel are you using to operate the board?

 I would really like to know which card(s) work for you. 

The ROM is designed so the CP/M BIOS loads at a specific location.
Here's what the memory looks like when you boot to the welcome screen.

DA00:   Code for Welcome Screen (3 choices)
Dxxx:    Code for the Monitor (uses routines in BIOS)
EE00:    CP/M BIOS

Now, when you load CP/M, a jump to the cold boot at EE00 causes the first XX number of sectors to be loaded from the file in "Disk-A" at DA00, so the memory now looks like this:

DA00:  CP/M  (CCP and BDOS)
EE00:   CP/M BIOS  (as loaded from Boot ROM, NOT from Disk-A).

So, you can have some other CP/M bios on "DISK-A" at sector XX+1, my ROM will not load that other BIOS, because my ROM should have all the BIOS you'll ever need for CP/M.

Now, back to loading files....    the only way I can think of doing it with what's there is.... 
1. Boot system to Monitor

2.  Transfer a file to Memory.
   You can do this with XMODEM.  from the Monitor, type:
   X U 100  <Enter>
Then start an XMODEM transfer from your terminal program.

Step 3.  You can either reset and boot to CP/M or from the monitor, type G DA00 to Jump to DA00 (the CP/M cold boot).

Step 4.  Rich Cini describes this CP/M instruction very well in his paper, I hope I don't mess it up here...
The program you loaded at 0x100 is still there.
At the a> prompt, type
SAVE  10  filename.ext
This will write 10 pages of 256 bytes from 0x100 to the file name you specify.

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