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Want to buy CPU RAM

PostPosted: Wed Apr 16, 2014 10:43 pm
One of my ultras fails to boot, CPU RAM died.
I know this is the issue because the sampler works fine after swapping the CPU RAM from another working machine.
Anyone have a machine for parts with a working CPU ram?

Re: Want to buy CPU RAM

PostPosted: Thu Apr 17, 2014 11:30 am
by mosrob
The CPU RAM (CN34) is standard DRAM that is also used as Sample RAM.
A long time ago I installed a 16MB DRAM PS2 module in socket CN34 and have more memory available for presets and sequences.
Actually the splitting of the CPU RAM between Preset Memory and Sequence Memory is 7677k / 512K (16MB) instead of 4487k / 512k (8MB).

Re: Want to buy CPU RAM

PostPosted: Thu Apr 17, 2014 11:45 am
Rob thanks for that it seems too easy, I think that maybe I have the wrong terminology, the board I need is the front one ( the one that holds the EOS) not the second one.
Perhaps this is this called something else? I would be delighted if it was just slotting in DRAM, could you shed a little more light on this for me?

Re: Want to buy CPU RAM

PostPosted: Thu Apr 17, 2014 12:37 pm
by mosrob
You are talking about the CPU Flash RAM SIMM of 4MB that is located in socket CN35.
Only the Ultra have a 4MB module. The classic line samplers use a 1MB (up to EOS 3.00) or 2MB (up to EOS 4.62) Flash RAM module.
Either you need a scrap E4 Ultra where you can take the Flash RAM SIMM out or you buy item #AP628-05 at EPR.

Building an own module is possible but the efforts are huge like:
- creating the schematics,
- making the PCB layout,
- PCB production (self or 3rd party),
- ordering parts (if you can get them),
- placing and soldering of the parts onto the PCB,
- programming of the Flash RAM SIMM in 32bit mode

Marjorie made a prototype of a 2MB Flash RAM SIMM for the classic line samplers and found that a blank Flash RAM SIMM is not recognized.
The sampler will not start as no Boot Code is found.
So the module has to be pre-programmed with the boot code (something like 28kB at the beginning of the memory range).
In this case you can copy the whole 4MB content from one working SIMM to a blank SIMM.

Beside the hardest part of getting the right Flash RAM ICs you have to have a programmer that supports a data bus width of 32bit.
The Sound ROM SIMMs and Sound Flash RAM SIMMs have a data bus width of 16bit which is easier to realize.

If you don't use the same Flash RAM ICs that are used on the original SIMMs you might only create Boot Flash ROMs which might also be OK.
But you might loose the option to store Presets in the Resident Memory (and maybe also storing changed settings of the SETUP). As no one has information about the source code of EOS, you don't definitely know if other Flash RAM ICs are supported than the used models from Sharp.

So the easiest way is to get a defective Ultra sampler or buy at EPR.

Re: Want to buy CPU RAM

PostPosted: Thu Apr 17, 2014 3:30 pm
Thanks for the detailed reply. How do you know so much about this stuff. I followed your info and yes I can buy a new EOS Ultra Boot Flash SIMM from for $78.62.
I think I will keep the ultra for parts unless I find a cheap spares/repairs Ultra i can cannibalize. Alternatively I could look for the 2MB (up to EOS 4.62) Flash RAM and go without EOS 4.7 on this machine. Will this work in an ultra? Do you know the part number to search for?

Re: Want to buy CPU RAM

PostPosted: Thu Apr 17, 2014 8:08 pm
by mosrob
JAHFUNK wrote: How do you know so much about this stuff.

I'm interested in building Sound Flash RAM SIMMs. Therefore I had a conversation with Marjorie and investigated on my own, also by taking a look at the technical documents of the E4.

Before purchasing a new Boot Flash SIMM, you should think about fixing the SIMM.
This can be easier than it might look at first sight.

Worst case would be a damaged wire/line inside of the PCB. In this case you need a new PCB.

The weakest parts are tantal capacitors. The capacitors are for stabilization of the power supply (+5V).
If any of them is broken, then errors might occur.

When you take a look at the SIMM you see:
- 2 Flash RAM ICs (U1 & U2), model Sharp LH28F160S5NS-L70
- 1 (Farnell) 74ACT138 3-to-8 decoder (U5), package SO-16
- 2 Tantal Capacitors (C14 & C15), value: 2,2µF, 16V, 10% tolerance, SMD package B
- 10 ceramic capacitors, value: 100nF, 16V, 10% tolerance, type 0805 (imperial)
- 3 resistors, 0 ohm, SMD package 0805 (imperial)
- 2 resistors, 33 ohm, SMD Package 0805 (imperial)

I recommend checking the capacitors first and replace them if necessary.
Components like resistors and capacitors are checked by desoldering at minimun one side or the complete component and measuring the value with a multimeter.
If a value of 0nF (capcitor) or "out of range" (resistor) is displayed then the component is dead.
In case of the 0 ohm resistors, a value of close to zero ohm is normal as this is in the range of the multimeters measurement accurracy.

Part no. of the tantal at 478-3879-1-ND
Get the "cut tape" version.
If you have a local supplier where you can purchase SMD parts without being charged 12 GBP for shipping: Go ahead!

If you have to replace one of the Flash RAMs then you need a programming device to copy the content of a working Boot Flash SIMM to the replaced Flash RAMs.

Re: Want to buy CPU RAM

PostPosted: Thu Apr 17, 2014 9:46 pm
Thanks Rob
That's all sounds a bit beyond my skills, but if it's useful in your SIMM experiments PM your address and I will post it, you're more than welcome. :grin:

BTW who's Marjorie?