Re: New GS/new accelerator

[supertimer@aol.com (Supertimer)]

bobryan9@my-deja.com wrote:

>Facts:
>Apple IIs have a 1 Mhz bus.
>1 Mhz video

Yes.  The IIGS CPU gets to operate at the speeds of 2.6Mhz
and 2.8Mhz depending on access to RAM or ROM, though.

>Apple II accelerator (TWGS)
>can run at 16 Mhz if you're lucky
>boosting speed from 2.8 to 7Mhz seems like a big increase when you run
>programs
>boosting speed from 7Mhz to 15Mhz seems like a very small increase when
>you run programs

Not entirely true.  Boosting speed from 2.8Mhz to 7Mhz
actually seems to have a very modest effect.  Boosting speed
from 7Mhz to 10Mhz will make things seem much smoother.
I have a 12.5Mhz TWGS and I can tell you that 12.5Mhz
seems to smooth things out A LOT compared to 10Mhz.
Only at 12.5Mhz do things actually seem snappy.

Given the speed curve I've seen with increasing Mhz of the
CPU, I think that the 25Mhz is probably when you will
stop seeing much of an increase due to the bus (although
cached code will continue to increase in speed).

>Apple II accelerators can have a 100Mhz processor, and still be hardly
>faster than a 15Mhz accelerator, because of the bottleneck of the 1Mhz
>bus and 1 Mhz video.

Probably 25Mhz is where one would stop and figure it would
not be worth it to change speeds further.  This is my
extrapolation based on the differences I've seen while running
my TWGS at different speeds.

>You want an Apple II accelerator.  I do too.  I want my Apple IIgs to
>go fast.
>
>You will not get an Apple II accelerator that will go very much faster
>than 15Mhz that will plug directly into the Apple II and output video
>through the video or RGB connectors on the back of the computer.  It
>just won't work.

It won't work because of the limitations of the components in
the TWGS and ZipGS, not because of anything in the IIGS
or the 65C816 CPU.  The Commodore 64 for example can
run the 65C816 at 20Mhz with the SuperCPU chip and that
is a lot faster than the 10Mhz version that was never made.
SuperCPU can do it but TWGS cannot because TWGS
(and ZipGS) was made at a time when 20Mhz processors
were not available.  Thus, the other components on these
cards do not have the tolerances needed for 20Mhz or
higher operation.

I'd like to stick the IIGS into a Cryotech PC tower case
and use the cooling system to deep freeze the TWGS to
see if it will go very much faster.  Considering that this
case/cooling system turns a 700Mhz AMD Athlon CPU
into a 1Ghz unit, I'll bet the TWGS will go at least 20Mhz
with it.

The nice thing about the Cryotech case is that moisture
won't condense on electronic components.  There is
a heater built into the cooling system that extracts the
moisture before this happens.