Atari ST Memory Upgrade help

[chinny_reckon]

I have an Atari STF 512k with C103414-001 Rev 1 board. I wish to upgrade to 1MB. It currently has 4x OKI M514256-10 memory chips with 4x accompanying AE6224ZAA831 capacitors. It has space for 4 more chips and 4 more capacitors (*See picture). I presume that I just have to fill the empty spots with the same chips/caps as in the full spots??? I have read that the AE6224ZAA831 caps are 100nf caps. Is this correct? Can any 100nf caps be used? I am unsure what memory chips are compatible. I have found this item which seems to be the same part number although it has a stock chip photo so im not sure: http://www.bauteilshop.at/Integrierte-Schaltungen/Speicher--Memory/DRAMs--SDRAMs/DRAMs/41256-3390.html . Should I buy these or can someone advise me on where to source the correct chios?

 

thanks in advance

[TZJB]

On 12/11/2023 at 12:57 PM, chinny_reckon said:

I have an Atari STF 512k with C103414-001 Rev 1 board. I wish to upgrade to 1MB. It currently has 4x OKI M514256-10 memory chips with 4x accompanying AE6224ZAA831 capacitors. It has space for 4 more chips and 4 more capacitors (*See picture). I presume that I just have to fill the empty spots with the same chips/caps as in the full spots??? I have read that the AE6224ZAA831 caps are 100nf caps. Is this correct? Can any 100nf caps be used? I am unsure what memory chips are compatible. I have found this item which seems to be the same part number although it has a stock chip photo so im not sure: http://www.bauteilshop.at/Integrierte-Schaltungen/Speicher--Memory/DRAMs--SDRAMs/DRAMs/41256-3390.html . Should I buy these or can someone advise me on where to source the correct chios?

 

thanks in advance

 

This Atari ST model uses surface mounted RAM known as small outline J-lead (SOJ) which normally requires a hot air re-work station to install or extract. See the middle item below.

 

 

The RAM you have listed is 20 pin dual-in-line (DIL) and is the wrong type for your application.

 

The de-coupling capacitors are generic/standard 0.1 uF (100 nF) ceramic.

 

New 514256 SOJ chips seem very expensive.

 

However you may be able to source the 514256 SOJ type RAM from old 256KB 30 PIN 8bit SIMM modules of the three chip variety, as you will be hot air soldering anyway.

 

They are normally quite cheap on eBay and will probably be faster memory types such as 60 or 70 nS whereas your Atari ST has 100nS RAM. You would need two 256KB SIMM modules for 512KB. Incidentally the third chip is for the 9th parity bit required in older PC's and would be redundant.

 

 

I hope that this may help you.

[351cougar]

if your doing the work anyway, why not go to 2 or 4 Mb? 

[+DarkLord]

3 hours ago, 351cougar said:

if your doing the work anyway, why not go to 2 or 4 Mb? 

 

I would second this. 

 

[TZJB]

11 hours ago, 351cougar said:

if your doing the work anyway, why not go to 2 or 4 Mb? 

 

I would normally agree with this sentiment if a hard drive is involved, otherwise 1 MB DRAM is more than sufficient for virtually all games.

 

It is a lot more cost and work to install 4MB DRAM to an Atari STF, especially if the MMU is soldered to the board, as the MMU adapter breakout plate will not have a socket to sit in.

 

Plus the Video Shifter chip may also need to be de-soldered in order to fit the Video shifter breakout plate.

 

There are commercial 4MB upgrade solutions but none support soldered MMUs, that I am aware of, except the new one from @tf_hh http://www.van-radecke.de/STUFF/tfhh_HW_info.pdf

 

When I asked Jurgen about this he said he had a hard time with this design due to a bad batch of branded RAM which he did not at first realise.

 

TFHH have a new stable batch now and installation instruction are here http://www.van-radecke.de/ST/ST4MB.pdf

 

[Atari030]

These boards are actually pretty easy to upgrade if you know what you are doing. 4MB is as simple as replacing the RAM and adding an extra address line to the MMU.

 

But, you have to desolder RAM from 4x 1MB SIMM's, desolder the existing RAM and surface mount the scavenged RAM. Its easier than tag style boards in that respect.

[TZJB]

19 hours ago, Atari030 said:

These boards are actually pretty easy to upgrade if you know what you are doing. 4MB is as simple as replacing the RAM and adding an extra address line to the MMU.

 

But, you have to desolder RAM from 4x 1MB SIMM's, desolder the existing RAM and surface mount the scavenged RAM. Its easier than tag style boards in that respect.

 

Thanks for the advice, I see what you mean.

 

The pinouts of the 514256 chips are similar to the 5144000 SOJ memory and just need A9 connected to the MMU.

 

That method sounds preferable to using the memory from 256KB SIMMs, but with this motherboard wouldn't you need one 4MB SIMM?

 

 

The 4MB SIMMs seem to have the HM514400 SOJ type memory with A9 on pin 5.

 

Do you have a picture of a completed installation by any chance, or any write-up on the process?

 

 

 

 

[Atari030]

Where you get the ram from isn't important, 4x 1mb or 1x 4mb. But yeah, that's how its done. I did this a couple of times over the years but I can't remember where I saw it originally.

[snarkdluG]

https://www.atari-forum.com/viewtopic.php?f=15&t=43308

[JamesWD]