TT Base ram to 8 MB

[Xevious]

Hi all,

Created a PCB that allows the replacement of the onboard 16 chips with a PCB that plugs in on the original sockets, and accepts two 4MB 72 pin SIMMs

Only change on the motherboard that is needed is the soldering of a wire to pin 34 of the ST-RAM MMU. Making it super easy to go back to stock if needed.

The fotos are of the 2nd version of the PCB (if you look closely on the foto you can see trace-cuts for instance), the final version is coming next week.

And as default I always have to order more than I need, so I have 8 PCB left over, anyone interested?
(Be aware that this PCB may not fit into all TTs since there are different version of the mainboard, and will also interfere with the Original Harddisk if it still fitted)

20191231_115438.jpg

20191231_115353.jpg

PS: I first need to assemble/test the new PCB, so I can add some of the assembly instruction to this post.
(Including the links to the materials)

PS: The tally so far:

czietz: 1
derkom: 2
Gaiyan: 1
DoG: 1

[Moulinaie]

Hi,

That's interesting !
The only problem is the soldering (most of all, you have to disassemble the VME case).
Is it possible to use a Minigrabber instead? Or does the signal of pin 34 appear elsewhere on the motherbaord? (into the ST RAM connectors?)

So, if I understand well, you have to unplug every RAM chip from the 2MB of the motherboard and plug your PCB instead, is it right?

Guillaume.

[Cyprian]

nice project.
few years ago Simbo modified original 4MB ST-RAM card to 8MB

[derkom]

Hi Xevious. I'm always interested in TT upgrades and would be happy to help you unload two of the extra boards.

[Gaiyan]

I'm interested in one!

[Xevious]

Hi,

That's interesting !
The only problem is the soldering (most of all, you have to disassemble the VME case).
Is it possible to use a Minigrabber instead? Or does the signal of pin 34 appear elsewhere on the motherbaord? (into the ST RAM connectors?)

So, if I understand well, you have to unplug every RAM chip from the 2MB of the motherboard and plug your PCB instead, is it right?

Guillaume.

So yes, remove all the original chips, and insert this board in place. And no, this pin is not present elsewhere on the board, at least not in the schematics and the board I've seen so far.

BTW: Removing the VME case is very simple. Especially when the TT is already stripped down The VME case is off-course placed back when all is installed.

[derkom]

So yes, remove all the original chips, and insert this board in place.

I'm not sure I would say "Making it super easy to go back to stock if needed" in that case.

[Xevious]

nice project.
few years ago Simbo modified original 4MB ST-RAM card to 8MB

Yes, saw that However I wanted something that was "easy"to install and could be put back to original. Also the st-ram expansion boards are harder to get by. And purchasing the seperate chips themselves is very expensive (<100 euro for 16 chips is already not feasible).

2 x 4MB simms can be had for ~10 Euro on Ebay. I've purchased both EDO and FPM, and both seem to work.......

[Xevious]

So yes, remove all the original chips, and insert this board in place.

I'm not sure I would say "Making it super easy to go back to stock if needed" in that case.

Ok, in my case the chips are in sockets, so I only need to remove those 16 chips and insert my board. And the reverse is done when going back to stock.

[frank.lukas]

... newer Atari TT boards has the 16 pieces 256kBx4 chips solder in with no sockets. Solder a wire at the TT SMD MCU is not so easy.

[1st1]

Two questions:

1. Is that board for the DIL or SMD style ST-RAM-board?
2. Why that wire? The upgrade by Simbo and the one from Lynxan do not need that extra wire.

I am interested in up to three of these boards, dependimg on question 1.

[frank.lukas]

Onboard ST Ram is always 256kx4 DIL 20pin

tt_ram.jpg

The PCB Layout fits with PGA Mainboards. SMD Board have solder in Dram without sockets ...

[Xevious]

Onboard ST Ram is always 256kx4 DIL 20pin

tt_ram.jpg

The PCB Layout fits with PGA Mainboards. SMD Board have solder in Dram without sockets ...

Yup this is one of the boards where this solution will not fit, as I mentioned in the OP.

[Xevious]

Two questions:

1. Is that board for the DIL or SMD style ST-RAM-board?
2. Why that wire? The upgrade by Simbo and the one from Lynxan do not need that extra wire.

I am interested in up to three of these boards, dependimg on question 1.

1-> DIL socketed chips.
2-> To access the MAD9 line that effectively quadruples the memory (Extra RAS/CAS Address line combination)

[DoG]

I am interested in one board.

[1st1]

I have to check. I have three TT, one is DIL, the other is SMD, the 3rd I don't know, just got it recently and did not open it yet. But I still don't understand that cable, Simbo and Lynxman's modification work without such a cable.

Is it still possible to place the harddisk between the PS/2 SIMMs?

And what would one of these boards cost?

[frank.lukas]

Simbo and Lynxman work and Upgrade are for the optional 2MB DIL ST Ram Board. So you have in total 10MB ST Ram, what is the max ...

TT-8MB-LYNXMAN.jpg

This Thread is for the ST Ram on the Mainboard ...

[Xevious]

I have to check. I have three TT, one is DIL, the other is SMD, the 3rd I don't know, just got it recently and did not open it yet. But I still don't understand that cable, Simbo and Lynxman's modification work without such a cable.

Is it still possible to place the harddisk between the PS/2 SIMMs?

And what would one of these boards cost?

Answer to you first question:

Simbo and Lynxman work and Upgrade are for the optional 2MB DIL ST Ram Board.
...
This Thread is for the ST Ram on the Mainboard ...

So the MMU used on the motherboard is AFAIK the same as used on the RAM daughter boards. On the motherboard ATARI physically didn't connect the line that is needed to adress the full space (MAD9), hence the need for that extra line.


Regarding the space for the hardisk: no (EDIT: Thinking about this, maybe if using those angled SIMM socket. Creating a '\_/' shape where the HDD can sit in between?)

Cost: 10 Euro.

[Xevious]

....., what is the max ...

....

Would be interesting to see if a fully modded daughterboard with a mod like this can enable maximum of 16MB?

[frank.lukas]

16MB ST Ram is not possible. 10MB is max because of the VME Bus Address Space.

[1st1]

The price is fair, but if I can't install the harddisk with this extension, then no, thanks.

[Xevious]

The price is fair, but if I can't install the harddisk with this extension, then no, thanks.

Np, less beer for me

[frank.lukas]

May be use 72 PIN RIGHT ANGLE SIMM SOCKETS. I do not know of Left Angle Sockets ?

[Xevious]

Hi all,

Created a PCB that.....

Update: Board is in production.

[Bikerbob]

Any news?

James