Nifty 400 memory upgrade, and couple of questions

[+x=usr(1536)]

Finally opened up the second of the 400s that I got a few months ago from @doctorclu.  Both machines came with 48K upgrades, and I found an Intec MM6448 inside of it.  Didn't get around to opening up the other one until tonight, and I was rather impressed with what I found.  Note that the Personality Board looks to be unaltered.

 

First off was the original 16K board, modified with 4864s.

 

 

Interestingly, there was an entire handmade logic board on the back of it to drive it.  The work on the board was impressive to say the least; it was very nicely put together and made me wish that my work was this good ?  Also note the socket labelled '2732' in the middle of the right-hand edge of the board:

 

 

Then I looked between the RAM card and the logic board.  The wirewrap work blew me away, and while it doesn't come across as well here as it does in the flesh, it's extremely well done:

 

 

Finally, here's a shot of the back of the main PCB.  Note the jumpers around the cartridge port and what I think is a diode down further down the board (look between joystick ports 2 & 3, and move about one-third of the way in to the left from them):

 

 

Anyhow, all of this leaves me with a couple of questions.

 

• Is this a known mod that anyone recognises?  I looked around but didn't find anything that was a total match.
• Is it a reasonable assumption that the 2732 socket is related to the jumpers running to the cartridge port?

 

My best guess is that the 2732 may have been used for cartridge copying, but I'm not totally convinced.  If anyone happens to know more, it would be greatly appreciated if you could detail it for me.

[sup8pdct]

The diode on motherboard looks like a factory mod. could be wrong tho.

The wire jumpers from cart socket to memory socket are std affair for a 400 48K upgrade.

The interesting part is the resistor between 2 chips and the 5th wire to memory socket.

It may be for to select the 4k rom in the $C000 to $CFFF area which is unused area in the 400/800. It was common to have some sort of monitor program in that space. Omnimon, supermon, The Hackers delight etc.

 

James

[+x=usr(1536)]

9 minutes ago, sup8pdct said:

The diode on motherboard looks like a factory mod. could be wrong tho.

That's what I thought as well.

9 minutes ago, sup8pdct said:

The wire jumpers from cart socket to memory socket are std affair for a 400 48K upgrade.

Yep, ran across them in reading up on a number of upgrades.  More:

9 minutes ago, sup8pdct said:

The interesting part is the resistor between 2 chips and the 5th wire to memory socket.

This is the one that was throwing me - I couldn't find reference to an upgrade that did this.

9 minutes ago, sup8pdct said:

It may be for to select the 4k rom in the $C000 to $CFFF area which is unused area in the 400/800. It was common to have some sort of monitor program in that space. Omnimon, supermon, The Hackers delight etc.

OK, that would make sense and may explain some of what looked to be jumpers on the logic board.

 

I wonder if the intent was to use the 2732 to store eight 4K chunks of data that could be jumper-selected, then mapped the $C000 to $CFFF space.  It would allow for multiple tools to reside on one EPROM.

[ClausB]

4 hours ago, x=usr(1536) said:

I wonder if the intent was to use the 2732 to store eight 4K chunks of data that could be jumper-selected, then mapped the $C000 to $CFFF space.

2732 can hold only 4K bytes total.

[ClausB]

4 hours ago, sup8pdct said:

The interesting part is the resistor between 2 chips and the 5th wire to memory socket.

That signal disables the motherboard's decoding of upper address bits. It could be used to disable OS ROMs and put RAM in their place as the XLs do.

 

So you could call this machine a 400XL.

[doctorclu]

On 11/26/2021 at 7:58 PM, x=usr(1536) said:

Finally opened up the second of the 400s that I got a few months ago from @doctorclu.  Both machines came with 48K upgrades, and I found an Intec MM6448 inside of it.  Didn't get around to opening up the other one until tonight, and I was rather impressed with what I found.  Note that the Personality Board looks to be unaltered. ...(clip)

 

• Is this a known mod that anyone recognises?  I looked around but didn't find anything that was a total match.
• Is it a reasonable assumption that the 2732 socket is related to the jumpers running to the cartridge port?

 

 

My best guess is that the 2732 may have been used for cartridge copying, but I'm not totally convinced.  If anyone happens to know more, it would be greatly appreciated if you could detail it for me.

 

Yep, that would be my Dad (Charles Goodwin's) work.     Wiring wrapping, piggy backing, why I loved Atari for as long as I have, he really put a lot into that.

 

He told me years later he loved it when I got an Atari 400.  He always wanted to play with an Atari 800 but they were expensive.  Got the 400 and he modified the crap out of them.  My 400 has all that and a 1200 xl keyboard adapted to it.

 

 

Years later we got the keyboard to fit in the case after much dremmeling. 

 

Anyway you should see the work he did to get that keyboard connected.  

 

So of those two 400s the one you opened was one he had to copy carts.  I think you just hold down option when you turn it on, let's you bypass the cartridge to load a cartridge downloading program we had at the time. 

 

The other 400 should be a the one Dad fixed up for my sister.

 

Good stuff. 

[+x=usr(1536)]

54 minutes ago, doctorclu said:

Yep, that would be my Dad (Charles Goodwin's) work.     Wiring wrapping, piggy backing, why I loved Atari for as long as I have, he really put a lot into that.

I had been hoping that you'd stick your head in to comment ?  Please let your dad know that I'm really blown away by the quality of his work; of all the homebrew stuff I've seen (or made) over the years, his knocks the spots off of pretty much everything else.

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He told me years later he loved it when I got an Atari 400.  He always wanted to play with an Atari 800 but they were expensive.  Got the 400 and he modified the crap out of them.  My 400 has all that and a 1200 xl keyboard adapted to it.

That's quite the mod (and I like it).  Did the F- and HELP keys work, or just START / SELECT / OPTION?

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Years later we got the keyboard to fit in the case after much dremmeling. 

 

Anyway you should see the work he did to get that keyboard connected.

I can only imagine (on both counts) ?

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So of those two 400s the one you opened was one he had to copy carts.  I think you just hold down option when you turn it on, let's you bypass the cartridge to load a cartridge downloading program we had at the time. 

Cool, thanks.  I'll give that a shot and see what I can find.  FWIW, the 2732 socket looked to be empty - I'm guessing that that was where the cartridge copier EPROM lived.  By any chance do you happen to know if the copier wrote to disk, tape, or something else entirely?

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The other 400 should be a the one Dad fixed up for my sister.

Ah, ok.  Yep, that one's a lot more vanilla - from what I recall of opening it up, it just has the 48K upgrade.  Haven't checked for XL / XE OS on them, though, so that might be worth a shot since he may have opened up the entire 64K to use.

 

LATE EDIT: scratch the XL OS idea; I just realised that both will boot to Memo Pad with no cartridge installed, so that's basically nixed.

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Good stuff. 

They're really awesome machines, and I'm thrilled to have them - they have a lot of really good character.  The cart copier machine could do with some video cleanup (I'm thinking recap), and I'm going back and forth on installing a UAV in it since it's already the more modified of the two.  Either way, they have a suitably-loving home ?