Date   : Fri, 07 Mar 2008 18:11:25 +0000
From   : pete@... (Pete Turnbull)
Subject: TUBE chip, accessing 'Parasite' side - 16Mhz 65C02S

On 07/03/2008 12:32, Fragula wrote:
> David Warrington wrote:
> 
>> I think ANYONE still using a beeb today should just "drop in a 65C02" or 
>> "65C02S" into their beeb to allow them to use BASIC4 and the "65Cxx" 
> 
> Gaahh It didn't work for me.. I had a few, probably fairly well stacked
> with hardware, model Bs, and the 'C02 (Literally CMOS, a 65C02P 2MHz)
> outputs didn't drive hard enough. The machine would boot sometimes if it
> felt like it, but was sure to crash within a few mins. Buffering of the
> address and data lines would be needed to make it happy. So not all
> 65C02s will work.

While that's probably true, I've done it on a few machines, with 65C02s 
which were probably Rockwell chips, and rarely had a problem.  A useful 
thing to try is swapping the data bus buffer 74LS245 for a 74ALS245 -- 
it's normally socketed and that's a standard Acorn-approved fix for a 
few timing issues, especially with second processors.  One of the 
machines I used to have like that was a fully expanded Issue 3, even had 
the Econet clock circuitry, several devices on the 1MHz bus, and two 
second processors running off the Tube power -- but then it did also 
have a fan!

-- 
Pete                                           Peter Turnbull
                                               Network Manager
                                               University of York