Hi Gary, I took a break from this “80486 project” and took a look at the switching back issue with the 80386. With both my boards I have no problem switching back to the Z80 using the SMB V2 with its K4 jumper 2-3. This utilizes the output bits 0,1,2 & 3 to select the TMA lines 1,2,3 &4. I use TMA0 for the 8086 family.
Jumpering the SMB V2 K4 1-2 and no P36 jumper, does not bring up the 80386. Adding the P36 jumper 1-2 then brings up the 80386, and allows a return to the Z80. However the TMA0 line stays low! If you also jumper P36 3-4, the TMA0 line goes low when the 80386 is in control. However its “Z” command does not switch back to the Z80.
However if you remove the K4 jumper on the SMB V2, the 80386 onboard port behaves correctly i.e. “Z” switches it back to the Z80 and TMA0 goes high again.
So….
If you are using the SMB V2, best to jumper K4 2-3. This will be the mode I will use anyway for future CPU boards (up to 15 on the S100 bus!)
If you use the 80386 onboard port, remove the K4 jumper on the SMB.
Have not tried the original SMB, but I suspect removing its jumper would be the same.
Let me know if this helps
John
PS I have not added Dave’s modes in all of the above.
From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of monahanz
Sent: Monday, February 2, 2015 4:24 PM
To: n8vem...@googlegroups.com
Cc: mon...@vitasoft.org
Subject: Re: [N8VEM-S100:6186] Re: 80386 CPU Board
My error Gary, the V1.49 is the most up to date version I have been using. Most recent changes are just for PM testing BTW. The core 8086 stuff really has not changed in a while.
I stuck in hardware currently. Could you carefully checkout the 80386 switching code. I seem to remember I used the old and new ways to switch TMA 0 line. Only the output mode will work for the SMB V2. With a logic probe see if you are getting signals.
On Monday, February 2, 2015 at 8:52:34 AM UTC-8, Gary Kaufman wrote:
Thanks for checking, I'll try tonight when I get home from work.
I believe I've tried both with 1-2 and 1-2,3-4 jumpered. I've also tried direct port access to EDh and EEh.
The latest monitor I could find on your site was V1.49
- Gary
On Monday, February 2, 2015 at 11:34:53 AM UTC-5, monahanz wrote:
Gary, just checked my board. I can get back to Z80 from 80386 monitor (V1.84) with the “Z” command if the P36 jumper is in 1-2 position. However NOT SO if it’s in 2-3 position. The latter is utilizing the SMB V2 to pull down TMA1 rather than the 80386 onboard port. I will look into it, but meanwhile check software for both CPU’s. I bet there is a conflict with either the (old) IN Port option to switch CPU’s or the newer Output a bit method.
John
From: n8ve...@googlegroups.com [mailto:n8ve...@googlegroups.com] On Behalf Of Gary Kaufman
Sent: Monday, February 2, 2015 5:27 AM
To: n8ve...@googlegroups.com
Subject: [N8VEM-S100:6179] Re: 80386 CPU Board
David and John -
I've read thru the '386 page dozens of times!
I have the SMB and can switch to the '386 board thru QIED, or output QOEE,01. Also the "W" and "O" commands both work. Unfortunately when I use "Z" to return the system hangs.
I can go back to the Z80 from the 6502, 8088 or 80286 boards fine.
I have P36 with 1-2 and 3-4 jumpered.
I do think it's likely a jumpering issue, but I'll also swap out all of the 74LS74's again once my Mouser order arrives. I've had a few flakey ones recently.
- Gary
On Sunday, February 1, 2015 at 11:02:55 PM UTC-5, monahanz wrote:
Gary I have written up a few notes/tricks on hardware debugging these types of CPU boards:-
On Sunday, February 1, 2015 at 8:24:54 AM UTC-8, Gary Kaufman wrote:
I completed the 80386 board yesterday, and after some confusion (on my
part) getting the monitor configured and jumpered correctly on the
MS-DOS support board it's running nicely at 32mhz using an AMD 80386-33
chip.
I'm running into two issues, and wonder if anyone has encountered them.
When I try to return to the Z80 using the "Z" command it hangs.
I've tried using a TX486DLC/E-33GA but it hangs after printing the
initial monitor prompt (at both 16 and 32mhz).
Thanks!
- Gary
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