Sram 74F189A

[David Halliday (Volt Computer)]

"Paul Maddox" <space_banana at hotmail.com> wrote:

>   HI I have a question Im trying to find some SRAM, the 74F189A
> would've been ideal.. its 16 by 4bit, yes 16 , its tiny... buts its all I 
> need.. I need to make a 24 bit wide byte with 16 addresses. and I need two

> of these.. so I need 12 of them..
> 
>   The main reason I like the look of these, 8nS access time... small is 
> quick.
> 
>   Now to the problem.. I dont think they make them anymore.. :-(
> 
>   So I need a way of getting 16 24bit wide numbers into a ram, but I need 
> two of them (cant be one chip) and it has to be < 30nS (maximum, less that

> 20 qould be prefferable).

Hi Paul,
I see, you're designing a high speed sequencer to go way beyond the 
200 bpm mark :-)

I haven't seen the 74xxx89 type RAMs for ages. But what about cache RAMs?
They are much larger than you need, but speedwise they might fit.
Don't know about I/O architecture, I'd suspect similar to static CMOS
RAMS, i.e. common in and out pins. Possibly mux'ed address lines, but
maybe that could be simplified if you don't need the full capacity.

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You can scavenge these from dead motherboards - 386 / 486

I got the idea from the BitScope page http://www.bitscope.com/

They use the same parts in their design for the same reason.