A4000 only seeing 2mb of fast ram not 8mb or 16mb

cugar124

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Hi Guys
I have had my board recapped battery replaced and new simm sockets put on by Mike he tested it with his simms and got 16mb but I have tried old ones I had and only 2mb shows also tried 2 new ones off ebay and still the same. Jumper is set to 1mb and I have tried it on 256kb as well. anyone got any Idea's what I need to do to get this to work. system has in it

MOBO b
Cyberstorm Mk2
Cybervision 64/3d
Ardine2
Buddha new version
Indi MK2 CR
New PSU Chucky one
Gotek for Floppy

Thanks Guys
 
SIMMS are either single or dual bank, and a bank is either 1MB or 4MB.

With 2MB, it would tend to be 1MBx 2 banks. With 8MB type it's 4MB x 2 banks.

I know the 4x 4MB (= 16MB) works, and therefore the 2x 8MB works, but not sure if the 2x 2MB (=4MB) works in place of 4x 1MB (=4MB). The skip-a-socket needs to be done for the 2x 8MB SIMMs due to socket wiring. I am not sure if that also applies to the 2MB type, but do try it.
 
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Battery had leaked a little bit but cleaned up long ago and new simm sockets fitted and traces checked by Mike
 
OK here is a new one got 4 replacement simms and low and behold it see 4 meg now so all simm sockets are seen but showing only 1mb ram even with the jumper set right any ideas?
 
Are you sure it's showing 1MB per Sim?

Have you tried one Sim in each slot in turn and then see what RAM it shows? And then try it in the next slot etc?
 
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Hi Guys sorry for so late a reply been a busy year!! OK finally got the board out and found that if I remove the jumper that sets simm sizes does not work I can leave it open on all three pins and no change every slot sees 1mb only any one any other Ideas please? I have tried 4mb in all slots no change!!

Tried 2 4mb different simms in all sockets and nothing in any other than the first but when all 4 fitted I get 4mb it seems Like a fault with one of the chips but which I wonder?
 
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now tried two double sided 8mb simms which dont even show 4mb between them
 
Does the Cyberstorm Mk2 have any RAM on it? Would it be smarter to put ram on the Cyberstorm Mk2 and just forget about fast mem on the motherboard?

 
If you has tested multiple simm ram and taken the machine back to the basics (no add-ons) and its till the same, have you had battery damage? If so was it cleaned up correctly?

There are a couple of chips arounf the RTC area that manage the fast ram so it could be traces or chip fault...

Thanks!!

now tried two double sided 8mb simms which dont even show 4mb between them
 
This is not trace damage. Are you using an ATX PSU with A4000D power adapter?
 
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Hi guys thanks for help yes battery leaked but fixed new simm sockets and recapped my mk2 is 060 with 128mb on the board.

Sent from my LM-G710 using Tapatalk
 
Tried my 030 board as well same result its been recapped too

Sent from my LM-G710 using Tapatalk
 
This is not trace damage. Are you using an ATX PSU with A4000D power adapter?

I will try again: Are you using an ATX PSU with A4000D power adapter? Or some kind of non-original power supply?
 
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Hi buddy in short that would be a yes as the PSU was replaced By Chucky with one of his upgraded ones which is really an atx supply with the amiga cables spliced in sorry about that
 
Hi buddy in short that would be a yes as the PSU was replaced By Chucky with one of his upgraded ones which is really an atx supply with the amiga cables spliced in sorry about that

Then most likely your problem is the missing _FAIL signal. I wrote an article about it before - recommend to check it out below and perhaps report back..

Symptom: While using a converted ATX PSU (or an ATX PSU with an adapter) only 1MB Fast RAM is detected per bank, so 16MB RAM shows as 4MB total, all other functionality is working on the board:

Cause: _FAIL (Pin1 - Grey) on the A4000 motherboard power connector is not wired up correctly to the ATX *PWR_GOOD pin (Pin8 - Grey). If you are using Ian Stedman's excellent ATX adapter design from 2016, the PWR_GOOD signal is mapped to the PCB side as a trough hole marked "fail".

Explanation: The POWER_OK signal of the ATX have to be connected to the _FAIL pin of the 4000 PSU connector. RAMSEY uses this signal to initialize properly. If it is tied to +5v, RAMSEY will read the 256k/1m ram jumper incorrectly leading to the fault above.

http://www.ianstedman.co.uk/Amiga/amiga_hacks/Amiga_PSU/amiga_psu.html#wiringa4000

Pasted-into-A4000-only-1MB-Fast-RAM-detected-when-using-ATX-PSU.png
 
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Ahh I see what you are getting at now sorry for being a bit slow will look it over during the holidays would explain an aweful lot. will pm Tbtorro and thank him
 
well you hit it on the head tried an Amikit ATX psu adaptor with an 550w psu and I get the magic 16mb
 
OK so in Full after testing my 4000 PSU with Chuckys and Tbtorro's help my ATX converted PSU was causing the ram fault this for me has been going on for years but now its cured as an old ex PC engineer I should have known better and tested the psu but hey its Miggy and its been fun to find out with the help of everyone here as well many thanks guys and happy Christmas 2019
 
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