Bus resistors upgrade

[exxos]

The bus resistors should be changed from 10K (or in some cases 4.7K) to 2.2K values. This is on the address and databus from the CPU. Resistor networks are 9 pin bussed types.

The ST bus is very weak and needs a lower value resistor array to keep the bus stable. Symptoms can be machine not booting when a cartridge is plugged in, or intermittent crashes or screen corruption in general and even some DMA related issues.

I will list motherboards as I work out where the arrays are located. There are so many revisions it may take some time before the list is complete. Currently I am assuming resistor pack numbers are common between ST/F/M & STE Machines.

SEE HERE HOW TO IDENTIFY THE SIL ARRAYS https://www.exxosforum.co.uk/forum/viewt ... =35&t=4730


C070789

IMG_0018.JPG

C103253

C103253.jpg

STE (EXTERNAL BLITTER)

NOTE: P100 needs to be 1.2K (if its not already).

STE.jpg

[DoG]

Changing bussed Resistor Packs (Arrays) on a Mega 1.

Yellow is address bus and red is data bus. On a Mega 1 the address bus is normally (if not always) 4,7k ohm and the data bus seems to be 10k ohm. Change for 2,2k Ohm.

MegaST1_RP.jpg

I've moved this to be in the correct location @DoG

[exxos]

C070523

C070523-001_AD.jpg

Thanks @Robson ;)