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Old 22 February 2021, 18:45   #1
ItsTheSmell
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Amiga Supra 500RX memory

Ive bought some ram to max out my Supra 500RX. Im getting bad memory when all 8mb is set. Ive swapped them around and all seem to be working when set to 4mb. so what could be wrong thats causing 8mb to fail the systest diagnostic test? Its an A500+ with 1 external floppy drive.
there looks to be no corrosion on any of the contacts (internally the 500rx looks brand new).
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Old 22 February 2021, 21:27   #2
lesta_smsc
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Isn't there jumper settings for this before you can use all 8MB?
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Old 22 February 2021, 23:01   #3
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Yes there is, I set them all to on (shorted I think) as per the instructions.
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Old 23 February 2021, 00:51   #4
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under systest, if i click direct memory scan it says 6mb total detected, fast ram 4.0MB when it is set to 8.0MB.
underneath it says WARNING: 4 holes in memory map?? (ram 000f00ff; alias 07f00000)

Under SupraRAMtest im getting the error at

Error at address 202ffc hex,
Bad bit was 00000000 00001101 binary.
Data bit D0 is probably bad.

here is the manual for the ram board: http://amiga.resource.cx/manual/SupraRAM500RX.pdf

if anyone can shed any light on this I'll send you a coffee.

Last edited by ItsTheSmell; 23 February 2021 at 01:30.
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Old 23 February 2021, 09:15   #5
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If you swap them around, does the error address change? In that case, I guess it's a bad ram chip. If not, it might be a bad solderjoint on the socket or a bad connection in the socket. Have you tried cleaning the sockets and pins on the ram chips? Do all pins on all sockets look ok or are some bent out of shape? Maybe post pictures of both sides of the board (sharp, detailed, well-lit, in-focus, please). I have the same ram expansion (working with 8mb) and I can try to compare the images with mine to see if something looks odd.
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Old 23 February 2021, 19:53   #6
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I had another go last night, the supraramtest software comes on 1.3 workbench. I kicked it down to 1.3 and rerun the test with jumpers set to 4mb and it seemed to pass all tests until I quit it. So I switched the jumper to 8mb and it failed everyone. It holts on each error which I didn't notice previously. One of the ram modules has a chip on top. Don't know if that will affect it. All chips looked new an were sold as new old stock. I will take some photos after my tea.
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Old 23 February 2021, 20:59   #7
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Which RAM did you upgrade with? Just wondering about compatibility.
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Old 24 February 2021, 00:46   #8
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I purchased the same modules I already had, they were recommended on BBOAH. Here is the link to 20mp images of the board, I have since pressed them down further but its still failing at 8mb.

https://onedrive.live.com/?id=5EF30C...F30C732C1D7342
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Old 24 February 2021, 09:20   #9
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If they all work when you set it to 4MB and just mount half the chips, and swap all the chips for the other set and they still work, I think we can say that the chips are ok and that the sockets labeled B1 and B2, which you use for the 4MB configuration are ok. Try to take a good look at the B3 and B4 sockets and see if one of the pins are bent a little or there are some dirt or oxidation (is that the English word?) on them that needs cleaning. Take a good look at their solder joints on the back from all angles. If you have access to a microscope or magnifying glass, use that. And check all other joints on all ICs and connectors, now that you are at it. I can't see anything from your photos, but bad solder joints can be hard to spot from photos.
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Old 24 February 2021, 18:34   #10
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Quote:
Originally Posted by jkp View Post
If you swap them around, does the error address change? In that case, I guess it's a bad ram chip. If not, it might be a bad solderjoint on the socket or a bad connection in the socket. Have you tried cleaning the sockets and pins on the ram chips? Do all pins on all sockets look ok or are some bent out of shape? Maybe post pictures of both sides of the board (sharp, detailed, well-lit, in-focus, please). I have the same ram expansion (working with 8mb) and I can try to compare the images with mine to see if something looks odd.



What power supply are you using? I'm using one from centurion, if you're using a 4.5amp or above that could be my issue.
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Old 24 February 2021, 22:40   #11
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Powersupply? None. It gets its power from the Amiga.
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Old 24 February 2021, 22:53   #12
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If my PSU isn't up to the job this might be why it doesn't run all the chips.
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Old 25 February 2021, 07:08   #13
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You use a separate psu for the ram expansion? I just use the original A500 psu and let it power the ram. No other expansions except the internal trapdoor 512K. If you use a separate psu for the ram, try disconnecting it. Ot could be that the power is unstable.
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Old 25 February 2021, 07:29   #14
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No I use the power from the Amiga, but, if my PSU is weaker than yours it might explain what's going on. I have a brick PSU I'll try it later.
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Old 25 February 2021, 07:38   #15
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I don’t think that 16 ram chips draws that much power. But give it a try. Remember to check voltage and polarity.
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Old 26 February 2021, 03:12   #16
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its not the psu. dont know what to do now.
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Old 26 February 2021, 12:23   #17
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If it’s always the same address, even if you shuffle the chips around, you should be able to identify which socket(s) that are problematic and check it for bent pins and clean it. Maybe replace it. Also check and clean the connector, both on the Supra and on the Amiga
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Old 26 February 2021, 12:24   #18
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If you know someone with another A500, you could test it there and verify if it’s the ram or computer that is faulty.
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Old 26 February 2021, 13:27   #19
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Did find this info -

https://bigbookofamigahardware.com/b...t.aspx?id=1079
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