25 January 2019, 19:57 | #1 |
Posts: n/a
|
0.5mb trapdoor expansion on 1mb A500+..still only 1mb ??
I have a A500+ with 1mb chipram internal.It should have been a A500 that is modified to A500+,so it´s not a native factory build A500+.
It´s a Rev 8a board and it´s Kickstart 2.0 I have a 0.5mb trapdoor expansion that I have tried to use also (it's working 100% on a regular stock 0.5mb A500 with Kickstart1.3) but the Amiga still only shows 1mb. I´ve posted about this issue on Facebook and a user suggested to solder a 74F139 IC onto location U32 and also remove solder from the jumper pads on U32. I´ve done this(and also added a socket for the 74F139) and still there is only 1mb shown. I have tried booting without the 74F139 but it just shows a green screen. With 74F139 added it boots normally but only shows 1mb,so the 74F139 is diong something to the system. So have anyone any ideas etc. why the A500+ don¨t show a total of 1.5mb ?? I have checked the traces using Amiga PCB Explorer site and as I can see/understand ,there is no broken traces (I´m not a electronics expert). I´ve tested continuity with a multmeter that BEEPS when probes are connected. Is there still some things/mods missing to the Amiga? Could there be mods to the trapdoor in order to work with a A500+ ?? |
25 January 2019, 21:26 | #2 |
Registered User
Join Date: Apr 2015
Location: Lisbon
Posts: 65
|
hello have you follow kipper2k guide? http://eab.abime.net/showthread.php?t=77705
|
25 January 2019, 22:27 | #3 | |
Posts: n/a
|
Quote:
Need to know why the 512kb trapdoor expansion is not added to the existing 1mb so it should have a total of 1.5mb. |
|
25 January 2019, 22:56 | #4 |
Registered User
Join Date: Apr 2015
Location: Lisbon
Posts: 65
|
migth be silly but what Agnus do you have (8375 or lower)?
is possible to see details pictures of thw motherboard? |
26 January 2019, 07:24 | #5 |
Registered User
Join Date: Jul 2012
Location: Kassel
Posts: 160
|
most old 0,5 ram extensions have a on/off switch, to use it the expansion in the a500+ the expansion must be switched OFF.
in a normal a500 is must be ON to use |
26 January 2019, 11:26 | #6 |
Posts: n/a
|
|
26 January 2019, 11:27 | #7 |
Posts: n/a
|
The switch is removed (always ON since it works in my regular A500) but I shortcurcuit the points but no result
|
26 January 2019, 14:05 | #8 |
Registered User
Join Date: Apr 2015
Location: Lisbon
Posts: 65
|
I dont own a 500+ but a friend of mine have one with commodore 500 ram upgrade and gets 1.5mb of chip ram. i dont know if 3d party ram expansions did something diferent from commodore ram expansion design.
Also if you have Agnus 8375 and did the same modifications like Kipper2k did, probably the ram expansion you got have some issues. I dont know what you can do more exept trying a diferent ram exp to check probably is better to provide more information with pictures of your A500 detaling the modifications you made and also the expasion card you have, others with more experience than me might help you. |
26 January 2019, 14:26 | #9 |
Posts: n/a
|
Well...It´s working now 100% ! <img src="images/smilies/biggrin.gif" border="0" alt="" title="Big Grin" smilieid="4" class="inlineimg" /><br />
<br /> Thanks to the Kipper2K tutorial even though I did refuse it first time. I did take a closer look at the modifications on finished board and compaired with mine and noticed that the JP3 solderblobs was different on mine and changed them to the way Kipper2K showed and wam bam there was 1.5mb ram.<br /> <br /> Thanks to all who took the time to post..most grateful <img src="images/smilies/smile.gif" border="0" alt="" title="Smile" smilieid="1" class="inlineimg" /> |
26 January 2019, 22:11 | #10 | |
Registered User
Join Date: Apr 2015
Location: Lisbon
Posts: 65
|
Quote:
|
|
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests) | |
Thread Tools | |
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
A500 1mb Chipram Upgrade - Trapdoor problem | Amicol | Hardware mods | 6 | 07 February 2014 00:37 |
Amiga 600 PCMCIA SRAM card 4mb + 1mb trapdoor expansion WANTED | lewis_slade | MarketPlace | 0 | 17 March 2012 10:28 |
Wanted: A601 1MB Trapdoor Expansion | Solid Snake | MarketPlace | 7 | 06 January 2012 19:38 |
A500+ 1mb RAM Expansion | PowerPie5000 | MarketPlace | 2 | 02 November 2010 22:19 |
Wanted: 1Mb expansion for the A500 Plus | Merlin | MarketPlace | 11 | 19 January 2008 20:05 |
|
|