Atari 8-bit DRAM Chips

{From a defunct Atari site}

just as an update to this thread. had a couple of convos assisting Thark today about different ram compatibility.

here's some notes worth remembering.

1] As I'd stated above - you can swap 64k ICs for 256k ICs. remember they'll function @64k limit tho.

2] if you want to swap out like for like - then use 4164 ICs. don't worry about the speed - atari were running on 4164 / 4264 in -2 and -10, but -10, -15, -20 are all good

3] if you can find them, 4264 ICs are backward compatible with 4164.

4] got a 600XL? you can do more or less the same as above - replacing the native 4416 IC with either 4164 or 41256 - again it'll max out @ 16k limit.

5] finally, the interesting bit. I've mixed 4164, 41256 and 4264 on the same 800XL board (with combinations of "2" "10" and "15" rated ICs...guess what? - it works and reports the standard 64k. My best guess? 8-bit machines - atari, apple and commodore would downgrade to the lowest rating inserted. so inserting -2 -10 and -20 on the same board make all ram run @ -20 (200 nano seconds).

Footnote added (Aug 29th)
I've recently seen an 800XL with all 4464 chips - not sure if atari used 4464s.
I also have two boards here that have recently been repaired (thanks Jon) - one had one faulty ram IC replaced - with a 3764 !!!
and my fully socketed board is fitted with 4864s!!!

- it's worth noting the combinations that work seem a lot wider than most of us would ever envisage.

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i would say ebay are ok - i've had 4164 ram form ebay and it worked fine
unless seller says "not working" you will be refunded if faulty.

all of these 64k chips should work in the 8-chip XL/XEs
µPD4164,HM4864, HM4864A, HYB4164, LH2164, M5K416, MK4564, MB8264, MB8264A, MSM3764, MN4164, MT4264, TMM4164, TMM4164A, TMS4164
4164

www.ebay.co.uk/itm/64K-Dynamic-RAM-64K-x-1-KM4164B-15-SAMSUNG-150ns-DRAM-NOS-8-Pieces-/272782861421?hash=item3f8320246d:gCcAAOxy2HFSVa1T
www.ebay.co.uk/itm/8pcs-new-old-stock-4164-upper-ram-chips-for-the-Sinclair-ZX-Spectrum-/182193323977?hash=item2a6b917fc9:g:CPMAAMXQySpRWZPN

also, it's worth considering 256k...yes, they'll only function as 64k, but they're cheaper
www.ebay.co.uk/itm/1X-HYB41256-12AA-8833-144-BIT-DYNAMIC-RAM-SIEMENS-DIP-16-ATARI-UPGRADE-120ns-/142285450607?hash=item2120dfad6f:g:E9IAAOSwtfhYqs-5