Re: A2GS Accelerator Thoughts

[Rubywand <rubywand@swbell.net>]

Supertimer writes ...
> 
> doug.cotton@cmdweb.com (Doug Cotton) wrote:
> 
> >While I posted this at the "Upgrade the A2GS" site, I thought I'd
> >also repost it here for those who don't frequent that area.
> >
> >Some observations on the suggested accelerator design:
> >

 ....


> 
> >Using a standard 65816 at 20 MHz is probably about the best you'll do
> >at this point in time... you might push it a little higher, but it
> >won't be easy.
> 
> Yup; I have to agree.  If it can be done on the C64, I can't see why
> it won't work on the GS...
> 
> >When I met with Bill Mensch in February of 1997, he indicated at that
> >time that another die shrink (for the 65816) may not be far off, and
> >that the processor should be capable of 40 MHz at that point.
> 
> When that happens, even our existing accelerators might benefit.
> Each component contributes to the maximum speed of the cards.
> If the CPU is rated at 40Mhz, then the overall tolerance of the
> system increases and a TWGS or ZipGS might push 20Mhz...
> who knows...
>

 ....

     My chief disagreement remains with the core "accelerator board"
approach. As both you and Doug acknowledge, a plug-in accelerator board
ends up bottlenecked by the GS bus. Even if you construct a kind of
'super accelerator' complete with 16MB or so of RAM, you still get
screwed by the bus for I/O and you still have not solved the problem of
needed video enhancements.

     You _could_ put 'everything' (fast uP, RAM, I/O, Video, ...) on a
plug-in New GS board and use the current GS as a front end. The problems
then become developement cost and the fact that you are locked into an
upgrade path which requires replacing an expensive all-in-one board
every few years.

     Using the current GS as a kind of front end is fine; but, if you
want real speed, you have to get away from the GS bus and into another
box with Slots for new plug-in cards.

     Unlike an all-in-one design, the cards in a separate GS expansion
box can be dedicated to a few simple functions (e.g. Microprocessor,
Memory, etc.) with corresponding low development cost. Once the
expansion bus details were made available, many individual users and
clubs could easily fabricate boards for the expansion box. Certainly,
any small manufacturer would have no problem developing and producing
cards in quantity.

     For more complex functions such as Video, disk I/O, Sound, ..., the
cards could be newly developed or they could be off-the-shelf PC boards.
Either way, the cards in the expansion box could be individually swapped
out for upgrading at low cost.

 

Rubywand