IIsi Overclocking - Experiences with NuBus Riser?

[Zhinü]

I’ve been reading about overclocking my IIsi to 25mhz, but I’m wondering about the use of a riser card. I’ve heard that it works by some people, and that it didn’t work (and the mac had to be dropped to 22.5 or 23mhz) by one person. I’m curious on the experience by other people. My riser has a Radius Pivot card for the monochrome pivot I use, so losing the riser means I can’t use the pivot. (At least not without using slow memory/soft pivot.)

What are you experiences with the 25mhz overclock and the nubus riser mixed together?

 

[slomacuser]

Works fine with mine IIsi with riser and radius card.

 

[Phipli]

I’ve been reading about overclocking my IIsi to 25mhz, but I’m wondering about the use of a riser card. I’ve heard that it works by some people, and that it didn’t work (and the mac had to be dropped to 22.5 or 23mhz) by one person. I’m curious on the experience by other people. My riser has a Radius Pivot card for the monochrome pivot I use, so losing the riser means I can’t use the pivot. (At least not without using slow memory/soft pivot.)

What are you experiences with the 25mhz overclock and the nubus riser mixed together?

If you fit a socket for the clock, you can easily switch back to the stock clock if something doesn't work.

 

[Zhinü]

If you fit a socket for the clock, you can easily switch back to the stock clock if something doesn't work.
View attachment 60790

Yeah that was the plan, it’s just that 45mhz crystals are kinda hard to find and I was planning on buying one now if I can.

Works fine with mine IIsi with riser and radius card.

Nice! Good to know.

 

[croissantking]

I have a Nubus riser and a Farallon Ethermac card in my IIsi that's overclocked to 25MHz, runs like a dream.

 

[shadedream]

I apparently got unlucky, mine has visual artifact glitching with my riser in so I run it without one and use a piscsi for ethernet now.

 

[croissantking]

I apparently got unlucky, mine has visual artifact glitching with my riser in so I run it without one and use a piscsi for ethernet now.

Oh really. I’d probably just put back the 40MHz oscillator if it doesn’t work right… the difference in performance isn’t that huge.

 

[Phipli]

Oh really. I’d probably just put back the 20MHz oscillator if it doesn’t work right… the difference in performance isn’t that huge.

@Zhinü
There is a chance that the NuBus card is what can't handle the overclock, so perhaps you could try another NuBus card if you can find one?

 

[shadedream]

Oh really. I’d probably just put back the 40MHz oscillator if it doesn’t work right… the difference in performance isn’t that huge.

It actually felt pretty zippy to me comparatively with the overclock. And I'd already tossed the other oscillator and was worried I'd burned one of the pads. Those things, especially the legs on the ground plane, are not easy to get out/clear the vias.

I have another IIsi with a damaged logic board, so I figured I'd use the riser in that one if I can get another board for it at some point.

 

[croissantking]

I socketed my oscillator just in case.

 

[shadedream]

Might have been ideal, but I didn't know where to start trying to find the socket and didn't expect problems only going to 25mhz. Maybe I'll find a different riser at some point that it works with as well.

 

[Phipli]

Might have been ideal, but I didn't know where to start trying to find the socket and didn't expect problems only going to 25mhz. Maybe I'll find a different riser at some point that it works with as well.

You can poke the pins out of a standard 14pin DIP socket. So you just grab one off eBay or Amazon.

 

[shadedream]

You can poke the pins out of a standard 14pin DIP socket. So you just grab one off eBay or Amazon.

Ahh apparently there's even someone selling them with only 4 pins for oscillators already on amazon for about the same price... might pick them up for when I do my Q700 in case I run into issues over there.

 

[JohnR]

I have two IIsi's, one of which is running at 25mhz. The only glitch I've struck with the overclock is graphical artefacts while using a Radius PDS video card. Nubus video cards seem to work fine with the riser. It's great to have a standard 20mhz one as well though! Good luck