Re: 14MHz 65816??

[rubywand@aol.com (RUBYWAND)]

In article <4ut0ev$r24@News.Dal.Ca>, tony@ccn.cs.dal.ca (Tony
Cianfaglione) writes:

>
>   I have been in contact with Western Digital regarding their 14 MHz 
>65816 chip which they tell me fits onto the accelerator cards such as the

>TransWarp GS or Zip GS.  They were not sure if it would replace the stock

>GS chip that plugs into the motherboard, which is what I want to do.  I 
>find the various accelerator cards too buggy to rely on.
>
>   They keep crashing in the middle of vital projects and I'm forced to 
>disable the cards and run at the native speed. ....

     The problem is, usually, not the accelerator card. The main problem
is that most power supplies have leads which are too skimpy. This results
in noise spikes which get propagated throughout the system. These spikes
can false-trigger IC's, mess-up memory contents, and cause all sorts of
glitches.

     The cure is to fatten-up the +5V and GND leads. (Unless you plan to
use a Second Sight board or an accelerator which gets power from the +12V
line, the +12V line usually does not need to be fattened.)

     Since you want to swap-in #12 gauge wires, the job is kind of a
bother. You must remove the old +5V lead from the Power Supply circuit
board, use a jewler's screwdriver as a drill to enlarge the hole without
ripping up the printed circuit, and solder the new, fat lead in place.
Route the lead through the slots intended for a fan on the side of the PS
box. Scooch-out the +5V prong in the plug-- use a small screwdriver to
push up on the prong through the side slot and pull--  cut off the old
lead, connect the new lead to the prong, re-insert the prong into plug.

     For GND, you can combine the two black leads and run them from one
point on the PS circuit board to one plug prong. #14 or #12 gauge wire is
fine for the new, second GND lead.

     Clean the motherboard PS connector pins.

     The result of these steps is much less resistance from PS to
motherboard. Noise voltage is cut, voltage loss is reduced, PS regulation
vis-a-vis on-motherboard voltages is better, and noise immunity is
improved.

     There's a decent chance that your system will now run free of
glitching with the accelerator plugged in. 


     Besides fatter PS leads, you can further reduce system noise by
popping out the motherboard and running #16 gauge wires from the +5V and
Gnd points on the PS connector to +5V and Gnd points on Slots 3 and 7.
While the board is out, go ahead and add +12V lines, too. (These run on
the underside of the board.)  The idea here is to compensate for the
skimpy circuit traces which feed power to the Slots.

     Before adding the PS and MB mods, our ROM-01 GS regularly bombed with
a 10MHz Zip plugged in. After the mods, the glitches are gone! A nice
side-benefit is reduced noise in stereo board sound output.
     

   

    



Rubywand