Re: 65816 200 MHz

[ferdimh@gmx.de]

On 12 Jan., 06:05, "Bryan Parkoff" <nos...@nospam.com> wrote:
>     I remember the 65816 200 MHz to be discussed earlier.  Do you wish to
> put 65816 200 MHz MPU chip on Apple II+?  It may need to redesign from
> scratch to build Apple II+'s motherboard.  The problem is that RAM, video,
> and MPU share the same osc chip.  It looks like 65816 MPU does not require
> external osc chip.  How would RAM and video operate at 1 MHz while 65816 MPU
> runs at 200 MHz?  Do it require a lot of cache?
>
You'll need 64K cache at maximum. And with today's prices I'd use it,
The simplest approach would be to clock RAM and CPU at a high
frequency and steal a cycle every time a scanner access is needed.
A more sophisticated approach would be to transfer video data to an
external video memory during unused cycles.
But I wouldn't user 200MHz, I'd start with 50 or so, where normal
"Cache" SRAM can be used which can be taken from old 486 mainboards.
Note that you'll need to slow down to 1 MHz for disk access and so on.
You'll also need shadow RAM for the ROM, because there are no ROMs
which are fast enough.

Ferdinand