Would a bog-standard 4164 be a suitable replacement for a MCM4517

Tony Duell ard at p850ug1.demon.co.uk
Thu Oct 21 15:02:03 CDT 2010


> 
>   On 10/20/2010 02:15 PM, Ethan Dicks wrote:
> > Could you use a 4164 instead?  (it might require a pull-up or
> > pull-down on pin 9 so it doesn't float).
> I'd just hardwire pin 9 to either +5V or ground.  Probably easiest to 
> tie it to +5V on pin 8.

I've replaced 4116s (3-rail) with 4164s in an 'emergency'. Bend out pins 
1 and 8 (-5V and +12V on the 4116, N/C nad +5V on the 4164) and jumpr pin 
8 to pin 9 (+5V on the 4116, A7 on the 4164) on the chip. Then plug it 
in. This, of couse ties A7 high since it's going into the 5V pin of the 
socket.

> 
> 16K DRAMs all required 128 row refresh in 2 ms.
> 
> 64K DRAMs came in two kinds.  Some required 256 row refresh in 4 ms, 
> while others (specifically intended for compatibility with 16K DRAMs) 
> required only 128 row refresh in 2 ms.  The latter kind will work with a 
> 7-bit refresh counter (e.g., 3242, or the counter built into the Z-80), 
> while the former will not.
> 
> However, in this case, you're only going to use 128 rows (and only half 
> of each row), so either kind of 64K DRAM should be suitable.

I asusme in all cases, the row that's seleected by a particular address 
is also the row that's refreshed by that address, so the rows that get no 
refesh are the ones that are never used in this arrangement. I can think 
of no sane reason to desing a DRAM any other way, but...

-tony



More information about the cctalk mailing list