Re: Recode to Play MP3?

[mdj <mdj.mdj@gmail.com>]

On May 24, 10:25 am, "Michael J. Mahon" <mjma...@aol.com> wrote:

> > The Transwarp only writes through when it has to (to the above
> > mentioned areas)
>
> That's interesting...  So most of the RAM is "stale" when running
> a TransWarp?  I wonder how much speed improvement this buys them?

It's difficult to say. The Transwarp certainly performs better at a
given speed than the Zip, but this is primarily due to never having to
invalidate cache for Main/Aux/ROM.

Certainly in any application where there's a lot of moving about of
data, like say a large AppleWorks word processor document, the
Transwarp feels a little snappier then a 4Mhz Zip.

The biggest improvement probably comes from never having to write
through to the zero page or the stack, the rest is probably
negligible.

I've often been tempted to fit a faster '02 and RAM to the Transwarp
and seeing if I can 'overclock' it. The primary clock seems to be
derived by doing a divide by 2 on the 7Mhz signal, so it's easy enough
to bypass the divider.

I'm a little concerned by the potential power consumption, and thus
heat that would result from it though and I'm not keen to bake one of
the GALS

> >>And maybe not even those, at least on a //e, since DMA is not allowed
> >>with most accelerators--certainly not with a Zip Chip.
>
> > The TurboIDE reportedly does 300kb/s under ProDOS 8, but I'd rather
> > have the aforementioned CFFA mods + my accelerator any day :-)
>
> So it uses DMA--I didn't know that.
>
> > I believe the Transwarp III claimed DMA compatibility, but those were
> > never released for public consumption.  Since the Zips cache is write-
> > through, it seems like an oversight that they didn't simply flag the
> > cache lines as invalid when DMA was activated. In the case of the
> > Transwarp I, it actually *is* a DMA peripheral.
>
> The Zip Chip plugs into the processor socket, not the peripheral bus,
> so it doesn't really know when DMA is activated.

Right. I figured it'd be simple enough to have a timer expire when the
master clock was deprived, and flag the cache as invalid, but perhaps
I am missing something. It's certainly a lot simpler than supporting
SYNC - you'd need transactional capabilities for that :-)

Matt