Re: Accelerator / VGA Graphics card

[Sheldon Simms <sheldonsimms@yahoo.com>]

On Fri, 24 Oct 2003 00:06:54 -0400, Charlie wrote:

> 
> "Sheldon Simms" <sheldonsimms@yahoo.com> wrote in message
> pan.2003.10.24.00.40.02.728516@yahoo.com">news:pan.2003.10.24.00.40.02.728516@yahoo.com...
>> On Thu, 23 Oct 2003 17:14:36 -0400, Charlie wrote:
> 
>> > I looked at their website and the Efficeon does seem to be a better
>> > choice although they are vague about the actual power usage.  The
>> > most I could find is that it uses under 7 Watts.
>>
>> I couldn't even find that. Do you have a URL for that?
> 
> http://investor.transmeta.com/news/20031014-119979.cfm
> 
> Here is the relavent quote from that page:
> 
> " the Efficeon processor family will be competitive with, or outperform
> competing microprocessors operating within critical thermal limits such
> as the 7W limit for typical fanless notebook designs "

Ok great. It would use even less power if clocked lower too.

>> > Would all Apple II memory be maintained on both the card and the
>> > Apple?
>>
>> The memory on the card would be the "real" memory. The main reason for
>> that is speed. There's no point in crippling the card's CPU by
>> requiring it to spend 90% of it's time waiting for the "old" Apple II
>> memory.
> 
> Makes sense, but wouldn't you still have to transfer the data from the
> card memory to the Apple memory and vice-versa.   Although, on second
> thought this would probably only have to be done during I/O.

There's actually no need to use the "Apple" memory at all,
although DMA could be a problem there.

>> > How do you handle Apple software that relies on precise timing such
>> > as disk I/O?
>>
>> The same way that traditional Apple II accelerators do - by slowing
>> down for a while after accessing timing-sensitive devices. How this
>> slowing down would be accomplished is yet to be determined. It may be
>> possible to do it completely in software, or it may require some
>> hardware assistance.
> 
> I'm thinking that doing it by just slowing down might be tricky.  A
> traditional Apple II accelerator doesn't have an emulator to deal with
> so slowing it down works, but an emulator would have to maintain the
> exact ratio of time needed per instruction as a real 65816. Otherwise
> you couldn't guarantee that a particular code loop would run at the
> correct speed when the processor was slowed down to 1MHz.

It isn't required that the card's processor be slowed to 1Mhz. It
would just have to drive the Apple II's bus at the correct speed.
It would probably be necessary to emulate every cycle of the 65816
execution. In other words, this "slowing down" might actually be
nothing more than the emulation code executing a 65816 instruction
and then waiting around for each tick of the 1Mhz clock and writing
the appropriate bits to the Apple II's bus. This could be done
mostly in software, but it might require the 1Mhz clock to trigger
interrupts on the card.

-Sheldon