STE video chip

[thesofa]

What is the difference between C300588 and C301712 ? Are they interchangeable?

[exxos]

I half recall trying this some years ago and the video was messed up on one of them, but I don't remember the exact numbers anymore.

EDIT:

Looked in my parts box and I have several C301712 chips. So assume those failed in my STE's so never listed them in my store or anything as couldn't work out what they were actually for.

EDIT2:

The STE's in the MB section seem to have the C301712 chips.. So

EDIT3:

Looks like one early STE had the C300588.

Maybe someone who has both chips can try them and verify ? I know I had problems with some chip numbers but was likely several years ago and does not look like I documented it anyway.But there definitely was some issues with some chips I tried.

[thesofa]

OK, thank you.

[exxos]

I did a quick test with the 301712 ( ST had the C300588 ) And as I thought, it has strange video issues! It does not happen with the C300588 .

Of course this is why I had a stack of them in my drawer because I did not have time to figure out another stupid "ST bug".

So IMO, only replace the chip with the same number as you took out otherwise you may well run into strange issues as well.

[thesofa]

OK, so have you got a C300588 in stock?

[exxos]

OK, so have you got a C300588 in stock?

Afraid not. STE stuff I don't really deal with. Even so, chips come from machines I scrap which isn't that often.

[troed]

And as I thought, it has strange video issues! It does not happen with the C300588 .

Interesting. The jump/blue-yellow issue is due to mismatch in timings between MMU and Shifter. The one-pixel distortions in the second part looks very much like what I had with the doubleST (overclocking the Shifter) when the voltage wasn't high enough.

/Troed

[exxos]

Interesting. The jump/blue-yellow issue is due to mismatch in timings between MMU and Shifter. The one-pixel distortions in the second part looks very much like what I had with the doubleST (overclocking the Shifter) when the voltage wasn't high enough.

Yep its odd. I'll just assume the chip is more suceptable to noise. Would follow the Atari trend.

[Steve]

@exxos that reminds me of what you said about this STe patch wire: https://www.exxosforum.co.uk/forum/viewt ... =51&t=4718

I wonder if that may have been to solve this issue.

[exxos]

@exxos that reminds me of what you said about this STe patch wire: https://www.exxosforum.co.uk/forum/viewt ... =51&t=4718

I wonder if that may have been to solve this issue.

Good thought. That STE does have that bodge wire in fact. But again, to basically have a extra pullup on a pin.. There was clearly issues else it wouldn't have the wire. Just another side effect of a cheap machine I guess.. I mean changing the cpu brand is enough to cause problems. The STE just isn't well designed and riddled with faults