Unusual mod found on lower board of XVI system

[BlueBMW]

I was working on an XVI today and when I took out the bottom board to do an SRAM battery I found some interesting mod work that someone had done.

I'm trying to figure out what the goal of these mods were... It appears they were messing with the pins that control the clock control of the floppy disk controller for selecting 8" or 5.25" floppy disks.

A wire goes from pin 19 of IC203 (NEC UPD72065C) to pin 9 of IC230 a 74LS367 which looks like the Y4 output pin.

Another wire connects pin 6 (A3) of IC230 to pin 3 of IC202 (SED9420CAC).  Pin 3 looks like some sort of clock control pin for floppy disk controller mode.

On the bottom of the board there is a wire connecting pins 10 and 7 of IC230.

There is also a 100pf capacitor between pins 6 and 8 of IC230 (the 74LS367)



Elsewhere on this board I noticed a 47uf capacitor added from pin 15 of IC229 (a 74LS244N) to one leg of R256.  On the bottom of the board there is a 68K resistor from pin 15 of IC229 to one of the pins of FB212 which seems to go to one of the mouse port pins.  Additionally there looks to be a diode added from pin 15 of IC229 to pin C3 of the large "T" connector that the mainboard ribbon cable connects to.



Datasheet for the SED9420CAC: http://pdf1.alldatasheet.com/datasheet-pdf/view/116631/ETC1/SED9420CAC.html

Datasheet for UPD72065C: http://pdf1.alldatasheet.com/datasheet-pdf/view/107833/NEC/UPD72065CG.html


Any ideas on what's going on here?  System was untested, I'm just now going through it.  I havent tried powering it on yet.

[lydux]

Look like more a fix than a mod to me...
The idea is just to filter and buffer the clock out of the data separator to the floppy controller.

The only reason I see to do this is a lazy IC202 which need some amplifications on its clock line.

Is the track between IC202 pin 3 and IC203 pin 19 broken ?
Also, what about IC230 pin 1 ? This pin should now control the clock.