A4000 RAM problem

[toRus]

I have an A4000 - revision 2B - that I can't make to recognise any fast RAM, either on the motherboard (4 x 4MB RAM or 1 x 4MB RAM SIMM module using an A3640 card) or/and on a CyberStorm MK2 card (2 x 16 SIMMs).

Has anyone faced a similar issue ? Is it likely a motherboard problem or do I have to try other SIMMs ?

[tonyw]

Do you mean that it recognises Chip RAM but not Fast RAM? If the SIMMs are not faulty, it would have to be one of the custom chips, like Ramsey.

ton

[toRus]

Thanks,
I 've got a rev11 Buster and a rev7 Ramsey chip. Do you think it is Ramsey ? Is it responsible for all fast RAM access or just for the onboard memory ?

The problem is that Ramsey is surface mounted so I guess I have a dead Amiga ( I can't afford sending abroad for repair.

[Quixote]

:-? Does the CyberStorm have jumpers on it relating to the memory settings?  You might want to double-check those.

[toRus]

There is only one jumper and AFAIK it has nothing to do with RAM :-/

[tonyw]

I don't know how the RAM on the CSII is addressed, but the RAM on the mobo is addressed by Ramsey. Ramsey provides the addresses, RAS and CAS lines, so I'd guess that would be the most likely culprit.

tony

Edit: Have you tried swapping the Chip and Fast SIMMs? Just to prove the Fast SIMMs are OK.

[Brian]

One should first make sure it's not faulty ram before playing around with custom chips, especially since it won't work neither on the motherboard nor the turboboard. I have a faint memory saying that the A4000 motherboard doesn't take EDO ram so perhaps you need (fast)pagemode modules, but for the turboboard that shouldn't be a problem so I suspect dead simms.

[toRus]

I should state that I have to use internal source (jumpers J100 and J104) for the CyberStorm while use external for the A3640,

My only hope is that the SIMMs are faulty. It's hard to find single sided 4MB modules these days. I will try bigger sizes with the CyberStorm over the weekend.

[tonyw]

Yes, that's right with the internal/external clocks - they have to be changed for each CPU board.

You can plug in bigger SIMMs (eg 16 or 32 MB), but they will only address 4 MB each. You can use 32 or 36 bit SIMMs too, any parity bits will be ignored.

Did you try swapping the SIMMs into the Chip RAM slot to test them?

tony

[toRus]

tonyw wrote:
Did you try swapping the SIMMs into the Chip RAM slot to test them?

I 've just tried all four 4MB and one 16MB single sided in the Chip memory slot. They were recognised but gave me only 1MB of chip mem.

[Dr_Righteous]

I've had this problem on my A4k... The problem I experienced was the SIMMs weren't seating properly because part of the plastic on the SIMM sockets was snapped off. Take all the SIMMs out, check for damage to the socket plastic.

If found, my fix was to apply (using a needle) a TINY amount of superglue on the outside edges to hold the module to the socket.

Oh, and I wouldn't recommend using a 16M SIMM... No combination of SIMMs larger than 4M each worked in my A4k.

[amigamad]

Are you sure there are no jumpers to set for fast ram? :-?

[tonyw]

There is one jumper for the Fast RAM - it's J852. According to my book, it's just to the right of the vertical backplane (under the CPU board).
It selects whether you have 1 M or 4 M SIMMs in the Fast RAM slots. Select "256k" for 1 M SIMMs, "1 M" for 4 M SIMMs.

tony