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RAM change to simm ?

Posted: Fri Dec 14, 2018 11:12 am
by exxos
As mentioned *somewhere* I talked about ditching the Falcon RAM boards in place for a 72pin simm socket instead. I am personally leaning towards that idea after the Falcon RAM card "disaster".

There may be some larger DRAM chips we could obtain.. There is the tiny SMT ones I used in my MMU adapter ( http://www.exxoshost.co.uk/atari/last/4MBMMU/index.htm ) Though frankly those are a PITA to solder. Though I am sure I saw some larger types somewhere about a year ago as used on some Acorn RAM boards. So if anyone can find any way to obtain 4 MB of RAM in 1 or 2 chips then let me know.. I am going to hunt around toward and see what I can find..

It still may be worth having the RAM as a addon card as if the DRAM goes off the market, it would render the MB useless if the RAM failed for any reason. In fact the Falcon RAM headers could remain, so that solves future problems. Then DRAM could be soldered onto the motherboard.


EDIT:

Might be a good solution..

https://www.aliexpress.com/item/10PCS-M ... 30696.html

OR ...

https://www.aliexpress.com/item/5PCS-AS ... 47085.html

.. which seem a lot cheaper!

Wonder if can get sockets for these things...

Re: RAM change to simm ?

Posted: Fri Dec 14, 2018 11:36 am
by rubber_jonnie
exxos wrote:
Fri Dec 14, 2018 11:12 am

It still may be worth having the RAM as a addon card as if the DRAM goes off the market, it would render the MB useless if the RAM failed for any reason. In fact the Falcon RAM headers could remain, so that solves future problems. Then DRAM could be soldered onto the motherboard.
Given the RAM problems I've had with some machines lately, DRAM soldered direct to the MB is a definite no no for me.

The Falcon RAM board is OK as a starting point, but it is kind of proprietary, so my feeling is that SIMMS should be the way to go, as they are standardised.

What about laptop Simm/Dimm modules?

Re: RAM change to simm ?

Posted: Fri Dec 14, 2018 11:42 am
by exxos
rubber_jonnie wrote:
Fri Dec 14, 2018 11:36 am
Given the RAM problems I've had with some machines lately, DRAM soldered direct to the MB is a definite no no for me.

The Falcon RAM board is OK as a starting point, but it is kind of proprietary, so my feeling is that SIMMS should be the way to go, as they are standardised.

What about laptop Simm/Dimm modules?
The problem with 72pin simms is the price for the socket is pretty high, like around £10-£15, its what is putting me off using them at the moment.

As for other modules, no idea how or what they are. If they are like 60ns DRAM then they may work, but nothing I ever looked into.

There are SOJ sockets, seem to be only in the USA on evilbay though :roll: https://www.ebay.co.uk/itm/QTY-15-42-PI ... 1206930396

I do agree soldering the RAM onto the board is a bad idea, not all the DRAM will work from China, so sockets are pretty much a must.

Re: RAM change to simm ?

Posted: Fri Dec 14, 2018 12:02 pm
by PhilC
+1 for the simm option from me. Although not cheap it won't take up much space and ram is still widely available.

Re: RAM change to simm ?

Posted: Fri Dec 14, 2018 12:21 pm
by rubber_jonnie
exxos wrote:
Fri Dec 14, 2018 11:42 am

There are SOJ sockets, seem to be only in the USA on evilbay though :roll: https://www.ebay.co.uk/itm/QTY-15-42-PI ... 1206930396
The only problem with that is they are surface mount sockets, meaning you will need to attach them to the board for folks who have no facility to do so (Like me)

I take it 72 pin SIMMs are the minimum you'd want to use?

Re: RAM change to simm ?

Posted: Fri Dec 14, 2018 12:36 pm
by exxos
rubber_jonnie wrote:
Fri Dec 14, 2018 12:21 pm
The only problem with that is they are surface mount sockets, meaning you will need to attach them to the board for folks who have no facility to do so (Like me)
Yeah, that is a problem. Possible DRAM could be soldered direct (not using sockets).

I am also half thinking that if the MB went more SMT stuff, I could get my assembly place to do all that work anyway. But of course costs increase that way over people soldering stuff themselves.
rubber_jonnie wrote:
Fri Dec 14, 2018 12:21 pm
I take it 72 pin SIMMs are the minimum you'd want to use?
72pin is just a easy thing to use, its one socket and 1 simm. 4MB are easy enough to find.

If people are happy enough to use simm, then I will add that on the board. I just was trying to keep the costs down for your guys as much as possible, so the simm socket price was pretty high, but its the easiest solution overall.

Re: RAM change to simm ?

Posted: Fri Dec 14, 2018 1:08 pm
by rubber_jonnie
exxos wrote:
Fri Dec 14, 2018 12:36 pm

Yeah, that is a problem. Possible DRAM could be soldered direct (not using sockets).

I am also half thinking that if the MB went more SMT stuff, I could get my assembly place to do all that work anyway. But of course costs increase that way over people soldering stuff themselves.

72pin is just a easy thing to use, its one socket and 1 simm. 4MB are easy enough to find.

If people are happy enough to use simm, then I will add that on the board. I just was trying to keep the costs down for your guys as much as possible, so the simm socket price was pretty high, but its the easiest solution overall.
These seem cheap enough https://uk.rs-online.com/web/p/products ... lsrc=aw.ds

I see the appeal of SMT, though having it pre-assembled might put me off a bit, as assembly is part of the fun for me. Also the additional cost is not something I'd like either!

Re: RAM change to simm ?

Posted: Fri Dec 14, 2018 1:17 pm
by exxos
rubber_jonnie wrote:
Fri Dec 14, 2018 1:08 pm
These seem cheap enough https://uk.rs-online.com/web/p/products ... lsrc=aw.ds
Need to be right angled as it will be under the keyboard...

Re: RAM change to simm ?

Posted: Fri Dec 14, 2018 1:44 pm
by rubber_jonnie
exxos wrote:
Fri Dec 14, 2018 1:17 pm
rubber_jonnie wrote:
Fri Dec 14, 2018 1:08 pm
These seem cheap enough https://uk.rs-online.com/web/p/products ... lsrc=aw.ds
Need to be right angled as it will be under the keyboard...
Damn..... :dizzy:

Re: RAM change to simm ?

Posted: Fri Dec 14, 2018 1:46 pm
by exxos
I will add the simm socket onto the design anyway. Aside from cost, its likely the best overall solution.