Atari 850 Serial/Parallel adapter teardown.
Posted: 26 Feb 2026 13:59
So I recently acquired an Atari 850 Serial/Parallel adapter so I thought I'd pull it apart and post here :)
Its a smallish unit with 4 serial ports and one parallel port plus 2 SIO ports that provide pass through for other devices :
It's aesthetic matches that of the 400/800 range of machines, and I'm not sure if there was any replacement for it when the XL range arrived.
Just four screws hold the lid on:
And once inside it's built very similarly to other Atari products.
The metal cover has a removable cover that allows access to what I can only assume is a ROM:
And once the entire cover is off you can see the ICs below:
From what I can tell the IC's Marked CO 10750 are known as the 6532 RIOT and were also used in the 2600.
The two other large IC's are the CO 10745-03 which is apparently a 6507 CPU as also found in the 2600, and the CO12099-03 and that is the ROM.
So a bit like the Atari 1050 FDD, this about half a 2600...
Will have to see if I can make it work next.
Its a smallish unit with 4 serial ports and one parallel port plus 2 SIO ports that provide pass through for other devices :
It's aesthetic matches that of the 400/800 range of machines, and I'm not sure if there was any replacement for it when the XL range arrived.
Just four screws hold the lid on:
And once inside it's built very similarly to other Atari products.
The metal cover has a removable cover that allows access to what I can only assume is a ROM:
And once the entire cover is off you can see the ICs below:
From what I can tell the IC's Marked CO 10750 are known as the 6532 RIOT and were also used in the 2600.
The two other large IC's are the CO 10745-03 which is apparently a 6507 CPU as also found in the 2600, and the CO12099-03 and that is the ROM.
So a bit like the Atari 1050 FDD, this about half a 2600...
Will have to see if I can make it work next.