a 64K SRAM should do the job with a latch to retain the row address. Here's how I did it for a Spectrum +2 - i used a 128K SRAM as they are more available.
The delay on CAS was needed for stability there
Peter Mulholland
@jaycee1980.bsky.social
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Grumpy old scouse git who fixes things, usually Amigas
