Imsai 8080 second graphic crt...

[Jan1980]

Hello.

Normally, my imsai is working fine. My setup is:

- original Intel 8080 cpu card
- 2x salota mixed memory ( 60k of RAM + Floppybios at F000h + homemade monitor programm at F800h )
- Interfacer 1 serial card
- versafloppy 1 floppycontroller
- 8" dual floppy station (no imsai)
- Esprit Terminal
- CP/M 2.2

Of course, my terminal, i can only use for text. I want to play with a little graphic programming. I have a SSM VB1C video card and i want to use both.
The SSM VB1C has 1k of RAM. I removed my hexmon eprom on F800h and adjusted the dip switches on the video card to F800h.
I connected the videocard to a little JVC CRT. When i start the imsai, on the little JVC is garbage. When i send 31h (for Ascii "1") to memory address
F800h, there is a "1" on the upper left corner of the crt. I tried different ascii-codes and different memory addresses. So, seems to be fine !
Always via toggle switches on the Imsai..

When i start CP/M from floppy. It also seems to work fine, but after a few entries to the command line, the computer stops working. I am not able to make a new entry
to the command line. I have to make a reset.

The memory chips on the salota mixed memory cards are UM6116-2L. The memory chips on the videocard are MM2102AN. So, all of them are static RAMs.

I tried without memory chips on videocard... the computer also crash..

I have the program "survey" to check memory.

Do you have an idea ??


THX !!

Jan

 

[Dwight Elvey]

check to see where it is putting the stack.
Dwight

 

[Hugo Holden]

One possibility although maybe not too likely is that the video card is either responding to an address range outside where you have set it, or maybe it has a fault where one of its output buffers is forcing data onto the address line when it is not being addressed, crashing the computer. So those output tri-state buffers could be worth checking. (but I'm talking like a person who thinks that all problems are in the hardware)

Also, your graphic video card (that I am completely unfamiliar with) might use an output line for making the CPU stall or wait like XRDY or PRDY and that might make it look like the cpu was locking up if your card was activating one of those lines.

( It looks like a very nice board, I just had a look at the manual. The only S-100 graphics boards I have used are the Matrox ALT-256, ALT-512, the Cromemco Dazzler and the Spectrum board).