Re: Hardware idea

[Dennis Jenkins <djenkins@usb.com>]

Geoff Oltmans wrote:
> 
> Dennis Jenkins wrote:
> 
> >         What RAM type would be better, static (no refresh needed) or dynamic?
> > I suspect that keeping dynamic ram saved during CPU power off would be a
> > pain.  (But I've seen it done before:  Inside my Zelda I Nintendo tape
> > is the standard two rom chips, a pal, a battery, a 2K dynamic ram chip
> > and a 6502....  I haven't a clue why they did not use static ram...)
> 
> From a power consumption standpoint, 32MB of DRAM will eat a battery
> pretty quick since it has to be refreshed. SRAM would be better in that
> regard. On top of that, with SRAM you don't have to worry about refresh
> logic either. And of course you'd need some bank switching hardware as
> well, and that will be a bit tricky with 32/64 bit wide RAM on an
> 8/16-bit computer.

	I completely forgot about bit width on the new ram sticks....  We could
use a 74138 and 4 74254's to latch which group of 8 bits from the 32 bit
space that we want...

	As for DRAM, I figured that a DRAM device would have no battery.  You
are correct, it would eat the battery alive.  Would it be possible to
use some of the Apple II's build in circuitry to do the DRAM refresh? 
How to the standard IIgs and IIe ram expansion cards handle refresh?


> 
> The card would be pretty complex component-wise, and is probably not
> feasible to build for a hobbyist.

Probably, but it would still be a cool thing to have.  Even without the
battery.  Actually, I would rephrase the above to "not feasible to build
for the average hobbyist".  I suspect that the people our there building
home brew ethernet, ide and SCSI cards could handle it.  Maybe if we
asked nicely, Mr. Empson might even help write the firmware.... :)

> 
> *Geoff!*

-- 
djenkins@usb.com                           Universal Savings Bank.

The three most dangerous things are a programmer with a soldering
iron, a manager who codes, and a user who gets ideas.