Cheetah Cub board

From: Doc Shipley <doc_at_mdrconsult.com>
Date: Wed Jun 9 19:13:40 2004

Tony Duell wrote:

>> So are these 256K per bank, or 256K per chip? IOW, if they turn out
>>to be compatible and I install 16 of them on the Amiga A2091, will that
>>be a 2MB or 0.25MB upgrade?
>
>
> Most DRAM chips are 1 bit wide. A 256K DRAM stores 256K _bits_ (not bytes
> or words), arranged as 262144 locations of 1 bit each. 8 such chips store
> 256K btes, 256K locations of 8 bits each (bit 0 is stored in the
> locations of one of the chips, bit 1 in another chip, and so on). 9 chips
> were used to store a byte + a parity bit (very common on PCs)
>
>
> 16 of them, used conventionally (which I assume the A2091 does) would
> store 512K bytes or 256K 16-bit words. It would be a 0.5M upgrade I guess

   So I talked to the memory guy here, and he says that the MT part
number is bogus. He says that there was a company doing counterfeits in
the late 80s and these are some of them.

   Back to the DRAM nomenclature, the 1 bit vs 1 byte explanation helps
a lot. I'm still confused about the multiplier.

   The Amiga docs show 16 256Kx4 DRAMs for a total of 2MB, so does that
mean that these chips are 256Kx1?


        Doc
Received on Wed Jun 09 2004 - 19:13:40 BST