By Otto Frederico Pereira de Carvalho Filho, Rio de Janeiro:

All I can say is: I'm writing this NOW on an A1200 equipped with a Blizzard 1260 that I overclocked myself to 66 MHz!

All I had to do was substitute the 50 MHz oscillator with a 66 MHz one (the later is smaller, but there is a second pair of holes just for it on the board: you only has to align the pin 1 with the mark on the board) and, THIS IS MOST IMPORTANT, fan-cool the '060, before you get annoyed with constant GURU's.

To do this, I got hold of an ordinary i486DX cooling fan, making some modifications on it. The type I got hold of was entirely metallic, with only four plastic hooks that are "inserted" into the heat sink and hold the fan, while at the same time gripping the PGA CPU. I cut the two outer borders of the fan, placing it right above the SIMM module.
Then I cut the trapdoor expansion lid to allow the fan to protrude from the bottom side. I had also provided some very tall rubber feet (about 5 cm high) to stabilize the 1200 and to allow room for the fan to "breath".

The result is: 51.6 MIPS instead of 38.7 (according to SysInfo 3.24), MAC video performance of 1.08 (using Shape Shifter 3.7, Savage_060 v2.2 and PAL HIRES video mode), according to SpeedoMeter 4.02. Even at DBLPAL No Flicker the result is 0.82! Every other parameter outperforms a Quadra 840AV by twofold!

The only problem is the heat. Because in Rio the weather can reach 42°C in the summer, I had to install another (bigger) fan inside the A1200 to pull air from the upper side of the board. I think this wouldn't be neccessary in European countries. But even with that extra work, I think it was worth every minute.

Another suggestion cames from Per Samuelsson:

Substitute the crystal with a socket, so you can try different oscillators with ease; also you can ask in the shop where you purchase the socket and the cristal to make the work for you if you are lazy or not so good with soldering iron.

A final note by Jeffrey D. Webster:

Just so you know.

66MHz overclocks don't work on most Blizzard 1260's that also have the Blizzard SCSI Kit IV on it.

Phase5, who obviously discourage the overclocking, claim that the access from the SCSI board to the accelerator "suffers a severe bottleneck..." when the 060 is overclocked.

We tried the overclock on 7 different Blizzard 1260's, each with the SCSI board, and it only worked on 2 of them.

We even tried swapping SCSI boards around... It is definitely the SCSI boards, and not the 1260 itself. For some reason some of the SCSI cards didn't care that the accelerator was at 66MHz.

Cannot overclock with RAM installed in the SCSI Kit, by Mark R. Smith:

Here is my story....

But first my config 1260/16Meg singlesided sim (60ns) and 1230 SCSI controller 32Meg (60ns) in a home brew tower.

I installed a 66Mhz X-tal Osc. and the A1200 didn't like it a bit (would't boot). I then installed a 60Mhz X-tal Osc. and it worked fine for about 5 minutes and then all kinds of wierd thing happened. So I put a fan directly on the 060 and it's been working fine for two weeks now. A 20% overall spped increase. Today I bought a 64Meg sim (60ns). Installed it into the 1230 SCSI controller. The computer would start to boot but then the green light would flash. To make a long story short I then put the 50Mhz X-tal Osc. back in and everything works just fine now.
The computer sees the 16Meg + 64Meg ram. The point I'm trying to make is that the Ram also determines how fast the 060 can be clocked to.

I like the fact that QUAKE plays faster but I also have a flatbed scanner and can get some VERY large files and the X-tra Ram is very usefull for the scanner and ImageFX......

For me speed limit is 50Mhz.
If I didn't need the memory then 60+

Overclocking & SCSI, by Ervin Pajor:

After a lot of research, both from this page and various newsgroup articles, I took the plunge and performed the necessary surgery on my 1260.

I actually had a socket inserted into the place where the 50Mhz oscillator was.
I bought both a 64Mhz and a 66Mhz oscillator, just to be safe.
I also bought a Pentium cooling fan, which is attached to a heat sink.
The heatsink is stuck directly onto the 060, using heatsink compound.
The fan had to be connected to the hard drive, for power.
All of these components were purchased from RS Components. I don't know if they have overseas offices. (Yes, they have them worldwide, Note from Dario)
I also had to raise the machine up about 2 centimetres (and of course, remove the trapdoor) so the fan would fit.
Because I have a socket in place of the oscillator, oscillators can be changed at will, so I performed various tests at 50Mhz, 64Mhz and 66Mhz.
The difference in various games and applications between the 64 and 66 rated oscillators is minor. But still noticeable.
The difference between 50Mhz and 66Mhz however, is not minor. It is huge!

For example, the Quakeplayer95 demo that runs at 9.8 fps at 50Mhz now runs at 12.7 fps (at 66Mhz). Quite a considerable increase!
(Of course, Quake is the main reason for the overclocking.)

ADoom runs at 21 fps instead of 16 fps. It is very smooth now.
The main reason I am writing to you though is to let you know about my experiences with the Blizzard SCSI-Kit.
Maybe it's because I used a certain type of memory (60ns 32Mb EDO SIMM).
I don't know. But I have NEVER had any problems with the SCSI-Kit.
None!
This surprises me as I've read a lot about people having problems with it after overclocking.
I can't have any memory on the 1260 itself due to lack of space after installing the CPU fan and heatsink (which means I can't use BlizKick - damn!) so the 32Mb SIMM is on the SCSI-Kit. (I used to have 16Mb, which was on the 1260 before overclocking).
But my Zip Drive (connected via the SCSI-Kit, of course) has worked flawlessly since the day I installed the SCSI-Kit. Before and after overclocking.
I don't know the revision of the SCSI-Kit, or the version of the driver.
Maybe I'm just one of the lucky ones...

Note From Dario:

Mhhh, my idea is that an overclocked board could cope only with one simm module due to differences in timing or perhaps with two identical simms...any report?

There is another interesting hack, adverted by Lorence Lombardo:

You can find it on Aminet at hard/hack/speedup.lha (here's a direct link).

This page hosted byGet your own Free Home Page