Hi David,
Happy New Year!
I’m not sure how you got that one. That board was the prototype of the final SMD 16MB board. It should look like the one shown here:-
http://s100computers.com/My%
20System%20Pages/16M%20RAM% 20Board/16MG%20RAM%20Board.htm Second picture from the top. The date is (28 Oct 2015).
That is the board I thought I sent to you and everybody else. If somehow you got the prototype, sorry. I have one spare production board left I can send it to you.
Yes that was an error on the prototype and was corrected on the production board. It was if I remember correctly, the only error BTW. I have removed these SMD RAM chips a few times in the past with an Aoye hot air gun + adaptor.
Unrelated, I have taken up your suggestion to do a dual speed clock circuit with GAL’s on the future 80486 prototype, good idea thanks, saves space as well.
I just did a GAL based 80386 prototype, got some RAM access/reliability issues with the above 16MB board (not seen on the older 4MB or mezzanine 16MB boards). Needs some more looking into, too early to know if it’s a CPU board or RAM board issue. However I’m seriously thinking of condensing all that 74LSxx stuff for 8/16 bit access into one or two GAL’s and doing yet another 16MB board. What do you think.
Can you let me know about the RAM board ASAP. I off to Europe tomorrow for a week. Can try and mail out a board today if I have time.
John
From: n8ve...@googlegroups.com [mailto:n8vem...@
googlegroups.com ] On Behalf Of David Fry
Sent: Saturday, January 3, 2015 5:34 AM
To: n8ve...@googlegroups.com
Subject: [N8VEM-S100:5962] 16MB Static Ram V3 (19 Oct 2014) Minor PCB Error ?
Hi John
I am in the process of testing my 16MB Static Ram board dated (19 Oct 2014) and I think I have picked up a minor error in the board
regarding the LED indicator lamps.
This board (19th Oct 2014) is the one with the LED's in the top left corner of the board labelled D2 (8R), D3 (16R), D4 (8W), and D5 (16W)
The problem I have noticed is that when performing 8 bit writes using the Z80 monitor D3 (16R) flashes instead of D4.
I have continuity checked the traces and have found the following:-
U7B Pin 9 (PX2) should connect to Pin 7 of U28 but is in fact connected to Pin 5 of U28
U16A Pin 1 (PX3) should connect to Pin 5 of U28 but is in fact connected to Pin 7 of U28
Somehow the connections to Pin 5 and 7 have got swapped even though the Net names on the schematic look correct !!!
Please can you confirm this with your board (19th Oct 2014) and post/email the Kicad files to the Wiki so that I can see where I can cut traces to correct with a wire patch.
regards
David Fry
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