Mega STe stability issues.

[Steve]

@Dbug yeah was me:
https://www.exxosforum.co.uk/forum/viewt ... 97&p=52817

[Dbug]

I finally received my parts for the machine (resistors, gals, etc...) and I looked on this thread about how to install the pullup on the FDC, but I realize that the location where people connects to get the +5v on the 1st pin on the SIL resistor does not match the Mega STe layout.

So before I do anything stupid, can someone confirm on the following picture that the 8 pins are to be soldered on the red highlighted area on the WDC... and what would be a proper location where to fetch the +5v for the last pin?

image_2022-06-04_095405878.png

Thanks :)

[DoG]

Pin 15 is +5V.

wd1772.gif

[Dbug]

Pin 15 is +5V.

I thought of that, but was wondering about why everybody was soldering to some other location on the motherboard instead of the chip's Vcc

[rubber_jonnie]

Pin 15 is +5V.

I thought of that, but was wondering about why everybody was soldering to some other location on the motherboard instead of the chip's Vcc

Should be fine off the IC but there are plenty of other places to pick 5v off, just check with a multimeter.

[Dbug]

Does that look ok?

image_2022-06-04_143720100.png

image_2022-06-04_143732160.png

I reverted the SIL (the marking is toward the rear of the computer) so the pin with a dot is closer to the Vcc pin.

[atari030]

That looks right. I'm interested to see the result.

[Dbug]

That looks right. I'm interested to see the result.

I need to do proper testing, but at least some large programs (big demos which required 4 megs of ram to load) seem to be more reliable, there were a couple of them which would crash at some point, and I ran them a dozen time in a row without any problem.

Next step is to add the VME card and see if the program which generated checksum errors is now running fine or if it still has these data errors.

[atari030]

That's promising. I noticed mine is a bit more stable with a gotek attached instead of a modern floppy. Leads me to think bus pull up will help.

[exxos]

That's promising. I noticed mine is a bit more stable with a gotek attached instead of a modern floppy. Leads me to think bus pull up will help.

One thing to bare in kind is there are 2 fixes doing different things. The DMA pullups which help with floppy and hard drive issues and the 1772 pullups which are needed for modern floppy drives like the MPF920. The gotek has the "1772 pull ups" already built in.