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AuthorTopic: A4000 RAM not recognized  (Read 1535 times)

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Offline koshman

A4000 RAM not recognized
« on: January 21, 2021, 09:40:22 PM »
Hi,

I'm having a pretty weird issue with an A4000.
She's been sitting in a closet for the last 2 years and as there is no chance I will be able to use her anytime soon I decided to take her out for a test and put up for sale.
Another thing I needed to do was test the Picasso IV I bought some years ago to use in the A4000 but never got around to setting it up.

After some attempts I was able to make the Picasso work in the 2nd slot from the bottom in 640x480 and 1024x768 resolutions and happily went to bed. The next morning I fired her up just to confirm and she wouldn't boot. After some fumbling around with no results I took the Picasso out and later got her to boot showing 1MB of Chip RAM.

The A4000 is fully populated with 2MB Chip and 16MB Fast and I could swear it was reporting all of the RAM correctly the day before. Now not only is no Fast RAM showing up but only half of the Chip RAM?!? I've seen people having issues with the Fast RAM before but the Chip RAM issue I don't recall ever seeing...
Of course I tried mixing the SIMMs and also tested a few other ones I had lying around.

I fear I must have damaged something while playing with the Picasso, Zorro slots are certainly no ZIFs and I may have been too rough...

I'll be very thankful for any ideas.

EDIT: I probably should have added some details about the config: Mobo is recapped with the RAM slots exchanged for metal ones, coin battery mod, KS ROM 3.1.4, A3640 3.2 recapped as well. I have the problem when booting off a CF HDD and also when booting a stock Install 3.1.4 ADF from a Gotek drive.
« Last Edit: January 21, 2021, 09:47:04 PM by koshman »
- Radim
 
A600 - 68020/33, 10MB RAM, 3.1, 2GB SD
 

Offline Pat the Cat

Re: A4000 RAM not recognized
« Reply #1 on: January 22, 2021, 01:39:41 AM »
Likely similar to;-

http://eab.abime.net/showthread.php?t=24348&goto=nextoldest

I have heard that memory access speed can be toggled on an A4000 between 60ns and 80ns. In software?

If so,I'd guess if you stick to 8MB 60ns fast page simms on chip RAM and alternate fast RAM slots, there's less to go wrong, You'll still be able to juggle sticks. (Although you'll still only have 2MB of chip RAM).

Anyway, if one of your double sided simms goes bad one side- it halves your 2Mb chip RAM simm into just 1mb? And makes all fast RAM vanish.

EDIT: i know, I know, most people insist you need one 2mb simm for the chip RAM. The Amiga doesn't check.

Thinking about it, maybe the reverse is also possible - if one side of your chip RAM simm goes bad, all your fast RAM goes up the swanny too.
« Last Edit: January 22, 2021, 06:11:37 AM by Pat the Cat »
"To recurse is human. To iterate, divine."

A1200, Vanilla, Surf Squirrel, SD Card, KS 3.0/3.z, PCMCIA dev
A500, Vanilla, A570, Rev 5, KS 1.2/1.3 Testbench system
Rasp Pi, UAE4ARM, 3D laser scanner, experimental, hoping for AmigaOS4Arm, based on Watterott Fabscan Pi
 

Offline Pat the Cat

Re: A4000 RAM not recognized
« Reply #2 on: January 22, 2021, 02:35:00 PM »
Anyway, if you start by plugging in one simm (2MB or more) into the chip  RAM socket (if you have one) and then one in the top fast RAM socket, that might at least get you a booting A4000 so you can which out which sticks are faulty.

You are supposed to add them one at a time from the top, for 1-2-3 or 4 MB (if the jumper is set to 1MB simms) or 4-9-12-16 (if the jumper is set to 4MB simms).

Avoid EDO RAM. It can work, but it's usually less reliable.

If you don't have a chip RAM socket, because some A4000s just have 2MB soldered onto the board, the problem may not be with the simms at all.

EDTI: Ok, on the Edo RAM thing, some accelerator cards use them well, but generally not A4000 motherboards.
« Last Edit: January 22, 2021, 05:03:19 PM by Pat the Cat »
"To recurse is human. To iterate, divine."

A1200, Vanilla, Surf Squirrel, SD Card, KS 3.0/3.z, PCMCIA dev
A500, Vanilla, A570, Rev 5, KS 1.2/1.3 Testbench system
Rasp Pi, UAE4ARM, 3D laser scanner, experimental, hoping for AmigaOS4Arm, based on Watterott Fabscan Pi
 

Offline koshman

Re: A4000 RAM not recognized
« Reply #3 on: January 22, 2021, 03:15:06 PM »
Thanks a lot for your help so far!

I can confirm I have Rev.B motherboard so it has 5 SIMM sockets including one for Chip RAM. Also all of the SIMMs I have here are single sided.
I'm going to be testing all the SIMMs I have in the Chip RAM socket to see if any of them reports full 2MB.
When you say add them from the top you mean start with Bank 0 - the Fast RAM socket closest to the Chip RAM socket?
- Radim
 
A600 - 68020/33, 10MB RAM, 3.1, 2GB SD
 

Offline Pat the Cat

Re: A4000 RAM not recognized
« Reply #4 on: January 22, 2021, 03:29:24 PM »
Correct. 1 in chip RAM plus 1 in 0,1,2,3

It makes sense to a a RAM check on each simm paired with a simm in the chip RAM socket.

The Amiga doesn't really check the whole simm, it assumes that if it can poke a few buytes and read them every so often, the whole bank is there and operating correctly.

This is why a faulty simm can seem to be working fine for a while.
"To recurse is human. To iterate, divine."

A1200, Vanilla, Surf Squirrel, SD Card, KS 3.0/3.z, PCMCIA dev
A500, Vanilla, A570, Rev 5, KS 1.2/1.3 Testbench system
Rasp Pi, UAE4ARM, 3D laser scanner, experimental, hoping for AmigaOS4Arm, based on Watterott Fabscan Pi
 

Offline arttu80

Re: A4000 RAM not recognized
« Reply #5 on: January 24, 2021, 06:19:41 PM »
Also all of the SIMMs I have here are single sided.

I read somewhere that CHIP RAM simm MUST be doublesided, but maybe that was wrong info? I have Rev B also and this has stock doublesided simm as Chip mem, others are singlesided.
 

Offline koshman

Re: A4000 RAM not recognized
« Reply #6 on: January 29, 2021, 01:13:10 PM »
The thing is these SIMMs were working in the A4000 in this config for years including a single sided SIMM for Chip RAM...

Anyway unfortunately after testing her further I'm now unable to even boot her up... Behaves like there's no CPU card....

I'm currently looking for a repair guy locally rather than risk damaging her in my clumsy attempts at revival... Have some tips for reliable guys already so hopefully she'll be up and running in no time.

In any case thanks for the tips :)
- Radim
 
A600 - 68020/33, 10MB RAM, 3.1, 2GB SD
 

Offline arttu80

Re: A4000 RAM not recognized
« Reply #7 on: January 30, 2021, 07:22:29 PM »
I would suggest to try other PSU before attempting repairs. You can install ATX PSU with adapter for Amiga, then you'll know better..

Like this;
https://amigakit.amiga.store/product_info.php?products_id=615
or
https://amigastore.eu/en/419-atx-to-at-power-adapter.html
 

Offline TjLaZer

Re: A4000 RAM not recognized
« Reply #8 on: February 19, 2021, 07:27:20 PM »
Get some Deoxit Fader F5 spray and spray all the zorro slots and card edges and see if that helps.  I got a Picasso IV working doing this.
Going Bananas over AMIGAs since 1987...

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