20 Dec
2005
20 Dec
'05
8:52 p.m.
The ZX Spectrum actually has jumpers on the board to specify whether
you're using "top half bad" 32Kx1 or "bottom half bad", for the
upper
32k. Of course the ones that always went were the bloody awful 4116es.
There was nothing wrong with the 4116. The problem was that that chip is
known to fail if it loses the -5V bias supply (this is documented in the
data sheets, which, IIRC, give a supply line sequencing order), and
Sinclair (as usual) really cut corners with the -5V supply. It tended to
fail (or at least fail to start up), and the DRAMs failed
I must have well over 100 4116s in running machines here, and I think
I've had to replace exactly one of them.
-tony