Msg: 7120 *Conference*

04-16-97 18:49:12

From: RON WIESEN

To : COMET _

Subj: REPLY TO MSG #7115 (WISH LIST)

Have an ExtRAM, don't have the quadruple XR4.  With a Rampac and ExtRAM combo,
upgrading to the XR4 isn't worth the extra battery drain.  Yea, I assumed the
XR4 fit without sticking out - that RAM and RAM ICs get smaller each year.

You meant to say "128K ROM chip with a ROMBO like carrier".  Well ROMs aren't
in as much demand as RAMs so the current breed of ROM ICs ain't so small.  But
either a single 128K (short enough to fit the 32-pin option Rom socket), or two
64K ROMs, or even four 32K ROMs (if flat enough) does the trick for Rick.

Contrare regarding power - ROMs take some.  They don't need "back up power"
because they have no refresh cycle like some RAMs.  I believe it's better to
tie multiple 32-K ROMs (e.g., four piggy-backed) to the address/data bus AND
TIE ALL THE CS (chip select) LINES TOGETHER.  This way you switch one of the
power leads - generally the negative power lead for minimum unpowered bus load
- to "engage" a ROM.  No address high-bit decoder logic for CS and no steering
logic - takes less logic, consumes less power, and loads the bus less.  Power
switching lends itself well to physical switches (e.g., rotary one-pole) but
that precludes "on the fly bank switching under software control.  Don't bother
me, but it may not be what fits Rick's wish list.  Power switching on the fly
under software control is possible, but "glitch dampening and timing" can make
it impractical.