Re: 10 mhz 6502's...

["Roger Johnstone" <rojaws@mac.com>]

In article 
<Pine.GSO.3.95.iB1.0.1010829233857.19326A-100000@halifax.chebucto.ns.ca>,
Tony Cianfaglione <ab616@chebucto.ns.ca> wrote:

> I was reading a page at: www.lowendmac.com on the Mac IIfx and it
> mentioned something about 2 - 10 mhz 6502 chips that were to be used in
> the IIfx for other things and take the pressure off the main processor.

I remember hearing this too, but I don't think they were 6502 processors, I
believe they were some variant of the Mitsubishi 50740 series of
microcontrollers. These chips are software compatible with the 65C02 but not
hardware compatible. Instead of having external address and data buses they
have built-in RAM and ROM. The IIgs uses one for its ADB controller. It runs
it at 3.58MHz, faster than the main processor.

> My question is were the chips made and what would happen if you plugged
> one into a IIc or IIe?  Would it simulate a zipchip or would nothing at
> all happen?
>
> Intriguing!

The 50740 couldn't be plugged in but faster 6502 chips are available.
Unfortunately if you just plug in a 4MHz 65C02 the Apple II will still run
it at 1MHz since the processor clock is generated on the motherboard. The
speed marked on the chip is merely the fastest speed at which it is
guarenteed to work.

--
Roger Johnstone, Invercargill, New Zealand

Apple II - Future Cop:LAPD - iMac Voodoo2 - Warcraft II
http://homepage.mac.com/rojaws
______________________________________________________________________

As a computer, I find your faith in technology amusing