Bus resistors upgrade

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exxos
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Bus resistors upgrade

Post by exxos » Thu Oct 24, 2019 2:05 pm

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.


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STE (EXTERNAL BLITTER)

NOTE: P100 needs to be 1.2K (if its not already).
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DoG
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Bus resistor upgrades (Mega ST 1)

Post by DoG » Mon Jun 01, 2020 2:16 pm

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

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Re: Bus resistors upgrade

Post by exxos » Fri Aug 14, 2020 9:17 pm

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Thanks @Robson ;)
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