9 Jan
2009
9 Jan
'09
8:55 p.m.
On Fri, Jan 9, 2009 at 11:19 AM, Dave McGuire <mcguire at neurotica.com> wrote:
On Jan 9, 2009, at 3:47 AM, Roy J. Tellason wrote:
True.
32kx8 sounds like a real handy size for some of
the things that I'd like
to do, with z80 and similar 8-bit parts.
Any suggestions as to where I might find some welcomed. I have 2kx8 and
8kx8 parts, but nothing bigger.
Maybe I should look on my old 486 boards?
Why bother? 6264 and 62256 chips are extremely common and much more
"standard". They go for a few dollars a tube all day long on eBay. And,
should you ever decide to "go that way" with a design, they're also
readily
available in SMT packages. Standard chips good. Weird chips from the PC world,
bad.
I'm not advocating the reuse of SMT 128K cache chips, but the 32Kx8
DIP chips from old motherboards have a JEDEC-compatible pinout (they
might designate various data or address bits in a different order, but
for RAM it's irrelevant), and are only 0.3" wide (meaning you can use
two 14-pin sockets rather than having to buy yet another footprint).
I've seen more than one hobby design that had a 0.6" footprint for a
62256 _and_ narrow pads for a 0.3"-cache SRAM (and even with SMT pads
inside that). It's possible to be flexible for no significant extra
effort.
The DIP cache SRAMs are no longer cheap-as-chips, but some of us have
a tube or two stashed away and I sure don't mind using them for
non-battery-powered circuits.
-ethan