68kMLA Classic Interface

This is a version of the 68kMLA forums for viewing on your favorite old mac. Visitors on modern platforms may prefer the main site.

Click here to select a new forum.
Clocking the IIsi
Posted by: bibilit on 2012-03-03 10:12:22
I had a spare IIsi board (the PSU went to Zuiko -a 68kmla member) so i decided to try to clock it to 25 mhz:

First step is to remove the 40 Mhz oscillator



The oscillator is easy to spot, it's located near the bank of ram and the logic board says it's a 40.00mhz oscillator, removing it is not easy:



Next step is to clean the board and to solder a dip socket (you can revert to the original oscillator if things don't go the way you want)



Of course, you should have a new 50 Mhz oscillator:

Image

Put back everything together,the setup is bulky now, but once again you can get back to 40.00mhz if required with the old and now removed oscillator.



As you can see the 50.00 mhz is also easy to spot on the new item 🙂

Next step is to boot the IIsi and to see how everything works (yes, this is a french system)



Done :lol: , the IIsi is more responsive, played two hours with it... the 68030 is running hot, but not much more than before, Ram doubler was properly set and i have now a spare upgraded logic board |)

I just spent one and a half removing and soldering the new items back, the best thing is that components were only a couple of $
Posted by: Trash80toHP_Mini on 2012-03-03 11:54:45
Great howto! I've got a kit for the IIfx that does the same thing, but comes with a cute little heatsink.

I'm definitely going to overclock my SuperIIsi™ but I shouldn't have any problems with the Proc Temp with the Rocket Accelerator in there. [}🙂] ]'>
Posted by: bbraun on 2012-03-03 13:38:57
Use Patater's Dhrystone on it. 🙂

Posted by: zuiko21 on 2012-03-12 15:31:12
Or Gauge series Clockometer 😉

Nice work! I think I'm going to do the same with my IIsi -- alive thanks to you 😀 But I don't have a 50 MHz oscillator, only one of 64 MHz... well, I'll put that on the Quadra 700 and then use its 50 MHz part on the IIsi :lol:

Posted by: theos911 on 2012-05-07 03:45:12
It seems your images have poofed.

xx(

Posted by: bibilit on 2012-05-09 02:00:02
here are the pictures alone

{edit - moved to OP}

pict02042.jpg

pict0224.jpg

pict0226.jpg

pict0228.jpg

pict0220.jpg
Posted by: uniserver on 2012-05-09 08:10:47
good info, i am running 7.6.1 right now on my IIsi and it's sluggish!(in 256 color) If i change it to Black and White it speeds right up,

i see your running OS 7.1, So Before and After, You said that it feels more responsive, on a percentage, how much faster?

also how would this OC effect the Math CO if installed?

i'm just trying to figure out exactly how much benefit is to gain from this,

Thanks.
Posted by: bibilit on 2012-05-09 12:29:45
i see your running OS 7.1, So Before and After, You said that it feels more responsive, on a percentage, how much faster?
i will say at least 15% more responsive than before, as i used a dip socket and managed to remove the old oscillator without any damage...i can try easily with the 40 Mhz and the 50 Mhz.

No Math CO installed.(not on this one at least, haven't tried with my other IIsi)

i am running 7.6.1 right now on my IIsi and it's sluggish!(in 256 color) If i change it to Black and White it speeds right up,
The inboard video is responsible for this (sharing the main system memory) and the fact that you are using SSW 7.6.1... 7.1 is pretty fast on the IIsi.

Also, what amount of memory are you using ?

As you have 5 units to play with, and parts to OC are really affordable (less than 5 $) it will be a shame not to have a try 🙂

Posted by: uniserver on 2012-05-09 12:43:55
i agree! i believe there is 4, 2mb Simms installed

well can you try a 64mhz oscillator? 🙂

maybe with HSF the cpu can be pushed faster?

Well sounds like i need a video card for this IIsi, looks like i could plug one in the riser, i would just have to relocate the network ports, 🙂

Posted by: bibilit on 2012-05-09 13:02:48
well can you try a 64mhz oscillator?
60 Mhz should be a maximum :

http://homepage.mac.com/schrier/stats.html

I just tried the OC because i have a logic board to spare, and as far as i know the floppy drive doesn't like to be pushed too far.(you cannot boot from it anymore)

Well sounds like i need a video card for this IIsi,
Was lucky enough to get a Raster Ops Paintboard LI with one of the IIsi's, huge difference !!
Posted by: uniserver on 2012-05-09 13:47:26
does the floppy boot 25mhz(50) or you are saying the floppy wont boot at 30mhz(60) ?
Posted by: Trash80toHP_Mini on 2012-05-09 17:03:02
Well sounds like i need a video card for this IIsi, looks like i could plug one in the riser, i would just have to relocate the network ports, 🙂
Which PDS NIC are you using? If it's the Asante with the removable ThickNet PassThru Board . . . you, sir, are in luck!

IIsiColorPivotII_PDS_Card_HackProject™

The Cards are dirt cheap from macmetex on eBay, you just need to build a cable, running wires from the jumpers (or their vacated thru-holes) on the Card to a Da-19 connector to bolt-up in place of the baled Thicknet DA-19 connector on the Asante Card. Using a DA-19 Gender changer is probably the easiest way to go, but I digress.
Posted by: uniserver on 2012-05-09 17:06:26
yeah it looks like i can take it apart, its got modules connected with ribbon cable.
Posted by: Trash80toHP_Mini on 2012-05-09 17:24:05
On the ASANTE Card, the ribbon cable connects to the Thicknet DaughterCard on a header. The Daughtercard connects to the identical header on the ThinNet/10baseT section. If you can unbolt the DA-19 and un-hook the DaughterCard, all you need do is hook the ribbon cable up to the remainder of the card in the same orientation as before and then you're left with the outlet for your Video Connector.
Posted by: uniserver on 2012-05-09 17:40:52
great now all i need is a video card,

do you think this one will work?

it's in the q700 right now.

IMG_0674.JPG
Posted by: Trash80toHP_Mini on 2012-05-09 19:44:05
That's a NuBus Card, so it's no good to use with your PDS NIC, just with the IIsi NuBus Adapter.

Do you want to run a Mac FixedRes CRT, a MultiRes/MultiSync CRT or use it with a modern LCD?

For either of the first two, the Radius Color Pivot II/IIsi is just about perfect . . .

The 832 x 624 x 75 Hz @ 8 Bit - 16" Color (Fixed Res Mac Monitor Standard) is particularly sweet on my 15" KDS/Radius LCD.

. . . you'll need to find a similar compatible MultiSync LCD in lieu of a CRT . . .

. . . unless I successfully get the card to output 60 Hz from its native 66Hz/75Hz vertical scan rates by UNDERClocking a Video Card?????? }🙂

. . . but that one's on the back burner ATM, there's more important IIsi fish to fry! [😀] ]'>
Posted by: bibilit on 2012-05-09 23:16:02
you are saying the floppy wont boot at 30mhz(60)
As far as i know, 25 Mhz will be Ok (the si's were designed to work that way from the start, and were indeed Under clocked)

30 Mhz is the limit, probably will work or not, but will probably not boot from a floppy, the floppy drive itself will still work properly.
Posted by: uniserver on 2012-05-10 12:12:10
wow that is annoying, well i guess 25mhz it will have to be, 🙂 gotta be able to boot from floppy 🙂

Posted by: uniserver on 2013-03-12 17:51:22
Just got mine to 29 mhz.

Serials / Floppy (Boots Floppys) all works very smooth!

Benchmarks:

viewtopic.php?f=8&t=19375&p=198475#p198475

IMG_1759.JPG
1