Atari 400 48K Memory Upgrade

[+Guitarman]

In going through my stuff, I found this documentation for hacking an Atari 400 16K memory module for 48K. Enjoy!!

 

 

 

Atari_400_48K_Memory_Upgrade.pdf

[mimo]

Thanks, that looks nicely detailed, I think I will have a go when I get some time

[Marius]

In going through my stuff, I found this documentation for hacking an Atari 400 16K memory module for 48K. Enjoy!!

 

 

 

Atari_40..._Upgrade.pdf

 

 

Today I did this upgrade, and I must say: that turned out VERY well. It's a very good document, no errors or problems. Two three notes though for people who still want to do his mod:

 

1) Do the piggyback soldering later in the process. First solder all wires to the bottom LS158 and the LS10

 

2) On three points you have to solder the leads of two wires to one pin of an IC. That can be hard when everything is already put together. First twist the two leads, solder that, and then make the connection to the IC-leg.

 

3) Pin 5 from the LS158 goes to pin 1 of the LS10. Since this is also connected to T8, I decided to solder this wire not to pin 1 of the LS10, but on the foilside of the PCB, I soldered this also to T8.

 

My PAL Atari 400 is now 48K and i find it very compatible. THE!CART works on my Atari 400 now (and not on my 48K Pal Atari 800...)

 

I also modded the cart-door-switch, since THE!CART does not fit with the latch shut.

 

I'm surprised by how compatible that 400 is now.

 

Next step is adding a nice VIDEO OUT to this thing.

 

Thanks a lot Guitarman, you have really made my day!

Edited May 28, 2014 by ProWizard

[morelenmir]

I cannot quite make out the number of DRAM chips needed. Is it '8'? Offhand I cannot remember the type used in the 800XL. Is it compatible?

 

Interestingly I have never come across the terminology 'foil side' for the surface of the PCB.

[flashjazzcat]

Yes - it's eight DRAMs, and I think they're the same as in the 800XL (timings might be different though - not sure offhand).

[morelenmir]

I will find a datasheet! This must be a fascinating relic PCB as I assumed it is only one-sided?

 

It is currently about a tenner for 8 on ebay. A chap from Aberdeen is selling them in their original bulk tubes, which is a pleasing novelty.

[ClausB]

Here's my version of the upgrade. Maybe it's easier to read.

http://www.atariage.com/forums/topic/123207-expanding-the-400/page__view__findpost__p__1488304

Edited July 1, 2015 by ClausB

[1050]

This must be a fascinating relic PCB as I assumed it is only one-sided?

Probably not. I'm thinking it's a misfire related to your earlier comment on 'foil' side misunderstanding. On this side of the pond, that would be the non-component side of a PCB. One side typically has the resistors and the other side has the 'foil'. But these were two sided boards in the proper use with 'foil' on both sides actually. Non-component side is too much typing so foil side is used instead.

 

Essentially, you've run afoul of a lazy american typist, we just happen to be used to such foibles. What you guys could call that side would probably have us at a disadvantage too?

[morelenmir]

Probably not. I'm thinking it's a misfire related to your earlier comment on 'foil' side misunderstanding. On this side of the pond, that would be the non-component side of a PCB. One side typically has the resistors and the other side has the 'foil'. But these were two sided boards in the proper use with 'foil' on both sides actually. Non-component side is too much typing so foil side is used instead.

 

Essentially, you've run afoul of a lazy american typist, we just happen to be used to such foibles. What you guys could call that side would probably have us at a disadvantage too?

 

I think I would probably refer to the conductive side rather prosaically as 'track side'. 'Foil Side' is actually far more descriptive and evocative. I think I will use it future! Of course nowadays with exotic things like five-layer boards - and probably more for all I know, my experience is very out of date! - I suppose the safest thing to say would be 'component side'.

 

One thing I really mourn though is the passing of through-hole circuits. SMT components are so tiny these days... I cannot even imagie putting together some of the daughter-boards that old Lotharek sells... You practically need one of those television-microscopes to do all your soldering through, not just to check the work afterwards for solder bridges!

 

I am a relic of the eighties.

[Joey Z]

 

I think I would probably refer to the conductive side rather prosaically as 'track side'. 'Foil Side' is actually far more descriptive and evocative. I think I will use it future! Of course nowadays with exotic things like five-layer boards - and probably more for all I know, my experience is very out of date! - I suppose the safest thing to say would be 'component side'.

 

One thing I really mourn though is the passing of through-hole circuits. SMT components are so tiny these days... I cannot even imagie putting together some of the daughter-boards that old Lotharek sells... You practically need one of those television-microscopes to do all your soldering through, not just to check the work afterwards for solder bridges!

 

I am a relic of the eighties.

I think it used to be called the 'solder side' by everything I ever saw. But that doesn't work now with SMD, because solder side and component side are the same on SMD, and mixed SMD/thru hole boards have two solder sides...

[1050]

Just as I thought, 'track' would have piled me up in the ditch where 'trace' makes the light come on.

 

Good line from a favorite movie made on your side of the pond:

"You guys invented the English language, but so far I haven't heard anybody actually using it."

[BillC]

Probably not. I'm thinking it's a misfire related to your earlier comment on 'foil' side misunderstanding. On this side of the pond, that would be the non-component side of a PCB. One side typically has the resistors and the other side has the 'foil'. But these were two sided boards in the proper use with 'foil' on both sides actually. Non-component side is too much typing so foil side is used instead.

 

Essentially, you've run afoul of a lazy american typist, we just happen to be used to such foibles. What you guys could call that side would probably have us at a disadvantage too?

I believe the common way of designating the sides of a through hole board is component side and solder side.

[atariry]

I wonder if anyone recognises the Atari 400 48k RAM expansion, attached (I couldn't see how to put it inline), please let me know.

 

 

This board is from the mid 80's when I had an Atari 400. Note I am in the UK, so this board might have only been available in the UK. In fact I have two of these boards. I recently bought an Atari 400 off Ebay, so that I could get the two boards working. This 400 was only 16k, so I can expand it to 48k and sell it on (and I can test the other board and sell it separately). I recall that there are two wires which need to connect to the motherboard. I have seen the mod wires needed for the official Atari expansion, and I am aware from studying the schematics that Atari omitted some parts on the 400 which would switch out the RAM when either a 8k or 16k cartridge/ROM was plugged in. Of course since the 400 was not expandable and only had 16k, so this circuitry was not needed (and shaved some $ off the BOM of the 400). I see that the mod wires connect the missing connections to the cartrigde connector to the Atari 48k expansion RAM card, which presumably has circuitry to switch off the upper 8k or 16k of the RAM.

 

I intend to reverse engineer the schematic and will post once completed. Nevertheless if anyone has any information about this board, especially where the two wires connect to, that would be most helpful.

 

--Atariry

 

 

Edited September 30, 2018 by atariry

[ClausB]

Here's a schematic of Atari's 48K board:

http://atariage.com/forums/topic/185500-using-the-atari-400-48k-board-in-the-800/?do=findComment&comment=2335665

It needs 4 wires soldered to the motherboard (S5, RD5, S4, RD4) and I can't think of a way to do it with only 2.

Edited October 1, 2018 by ClausB

[atariry]

Here is the schematic of the board (minus the two pull down resistors on the RD4 and RD5 pins which I forgot to add). Note that it needs 6 connections above and beyond what is available on the Atari 400 memory connector. Four of these connections use unused pins on this connector and route to pads R,T,M and N on the PCB. They will need wires added underneath the main PCB of the 400 to SEL4, SEL5, A14 and A15. Two other connections for RD4 and RD5 need flying wires to the main PCB (there are not enough spare connections on the edge connector). I have yet to add these wires to confirm my suspicions, but I will report back if it works!

 

--Atariry

[axeman]

Can someone tell me if I can use 4164 100ns ram chips for this mod ?

[axeman]

Yes I can but the Gary Crowell mod didn't work for me so tried the Claus B mod and it worked! 

 

Also works with SDrive Max

 

[Cmherndon79]

Hi,

 

Just wanted to say that I ran across this post after running into issues with the Gary Cromwell document.  I actually did the work 3 times, the first two learning because of the way it outlines the steps results in a messy looking mod.  I checked and verified all my connections on all three attempts and could never get it to boot.

 

I was able to get the @ClausB mod working on the first attempt.  Not sure if there are revision differences or something else that cause issues with the Cromwell implementation, but it just didn't work for me.  Thanks for posting the alternative @ClausB!

[WicoKid]

ClausB/Atari Age thank you for this design and thread....once I got rid of a bad 4164 chip, worked like a charm on another 400.