Typically the 486 DX-33 and the 486 DX2-66 are interchangeable. They both are 33MHz external, CPU that use 5 volts, the DX2 is "clock doubled" so internally or anything directly addressed by the DX-2 goes at 66 MHz, but the "speed critical" stuff goes at 33MHz or whatever it's decoupled bus is supposed to run at, the worst thing that could happen is that the 66 could end up clocked down if there is a jumper setting for your motherboard that is required for the 66MHz CPU to allow it to run at full speed. When the DX2 came out, it was basically a "drop-in" upgrade from the 486 DX.

The FSB for the DX2 is the same as the DX - 33MHz - only inside the chip goes 66MHz.

There were other versions of the 486 that went faster or slower bus wise, some could go around 50 MHz, but running the bus at that speed became really unstable for certain hardware, particularly expansion cards such as the graphics adapter as the timing would be too fast for the card to handle.

It will work, but make sure you use adequate cooling. A large heatsink or a fan would be a good idea. Hopefully your case is well designed and the airflow is good.

There is a special 'Overdrive' version of the DX2-66, which has a heatsink glued on. It is specifically meant for upgrading DX33-machines.

Ok thanks to all

but my test will have to wait

I've only a Cyrix 486 Dx2 50MHz (with green heatsink) and the 25MHz FSB could need jumper configuration

Scali wrote:

There is a special 'Overdrive' version of the DX2-66, which has a heatsink glued on. It is specifically meant for upgrading DX33-machines.

The peculiarity lies in the special heatsink?

I wouldn't waste your time going from a DX-33 to a DX2-50. The performance is more or less the same.

mav85ale wrote:

Scali wrote:

There is a special 'Overdrive' version of the DX2-66, which has a heatsink glued on. It is specifically meant for upgrading DX33-machines.

The peculiarity lies in the special heatsink?

There are other details...
Wikipedia has a nice overview: http://en.wikipedia.org/wiki/Intel_80486_OverDrive
So these chips are selected not to overheat with the attached heatsink. Regular 486 chips may run hotter (I've been using one in my 486 for years, it's a DX2-66, which I run at 80 MHz with a fan).
And they have some extra onboard stuff to make them more compatible with old 486 motherboards.
Note also that there are two versions, with different pinouts. One a regular 486-socket, the other a special 'OverDrive' socket.

Anyway, you need to match the pinout and the voltage of your 486DX-33. There are 5v and 3.3v versions of the chip. Older systems will use 5v. Newer systems may have jumpers to select between 5v and 3.3v.

I will check tonight the exact version of 486 installed

the real problem is the ram... 30Pin ram is really expensive e really rare
I think the maximum RAM supported is 16MB with 8x2MB

Usually 4MB simms work just fine. So max would be 4MB*8 = 32MB. Which is plenty.

4x4mb would be the best for me!
I did not find much information about it..
outside the PC it is identical to this

http://vinc.prv.pl/text/299e3ed5-1768.html

mav85ale wrote:

I will check tonight the exact version of 486 installed

the real problem is the ram... 30Pin ram is really expensive e really rare
I think the maximum RAM supported is 16MB with 8x2MB

It could not be. 30pin SIMMs must be used in packs of 4 for any 386DX or 486 CPU. And I believe it is a big possibility that, it will go up to 64MB (16x4) since even the late 386 boards had 16MB SIMM module support (hence 16x4=64) in 1993-94.

They are not the cheapest thing but it is still possible to have 16MB SIMMs new from OWC:

http://eshop.macsales.com/item/OWC/30PS16MB/

Good price but I do not know that can support 16MB modules

on this page, for a similar system report 32MB max ( 4x4MB )

http://scacom.bplaced.net/Collection/pc486/pc486.php

It's generally safe to assume 32MB is the maximum on 486 motherboards with 30-pin SIMM slots unless you can find documentation that shows 16MB SIMMs are supported. I have found support for 16MB 30-pin SIMMs to be the exception rather than the rule.

I got information about the CPU installed , the part number is SX419

http://www.cpu-world.com/CPUs/80486/Intel-A80486DX-33.html

"Use Intel ODP486DX-33, ODPR486DX-33, DX2ODP66 or DX2ODPR66 to upgrade to 66 MHz
Use Intel DX4ODP100 or DX4ODPR100 to upgrade to 100 MHz
Use Intel PODP5V83 to upgrade to Pentium 83 MHz"

mav85ale wrote:

"Use Intel ODP486DX-33, ODPR486DX-33, DX2ODP66 or DX2ODPR66 to upgrade to 66 MHz
Use Intel DX4ODP100 or DX4ODPR100 to upgrade to 100 MHz
Use Intel PODP5V83 to upgrade to Pentium 83 MHz"

Be careful with that list of options!
These options are valid upgrades for the *CPU*, as they are all 5v-compatible CPUs.
However, you also need to take the *motherboard* into account, since some of these CPUs require special sockets and/or special BIOS support.
For example, the ODP-CPUs need a separate 'overdrive' socket next to the regular CPU socket, with a different pinout. ODPR CPUs do not, they are a replacement for the regular 486 CPU and are pin-compatible.
And the PODP5V83 needs a 486-socket with an extra border of pins around it that the 486 does not use. Also, I have found that even some boards that have the required socket do not work with this CPU. Possibly because the BIOS does not recognize it.
Your Commodore machine is quite an early model, so I don't think it will even have the required socket for it.

On the motherboard is present a second socket, maybe for configurations 486SX + 487

Microsoft System Diagnostic report item "Weitek processor not present".. do you know anything about it? could support overdrive processor?

http://it.wikipedia.org/wiki/Weitek

As far as I know it's the ODP overdrives that go into the 487 socket.

My first 486 back in 1993 supported 8x16MB SIMMs for a total of 128MB. The board was some generic special. It wasn't that rare.

NJRoadfan wrote:

My first 486 back in 1993 supported 8x16MB SIMMs for a total of 128MB. The board was some generic special. It wasn't that rare.

I think my 486 is 91/92, do you remember if they were SIMM 30pin or 72pin ?

I tried the Cy486DX2 50MHz, without jumper setting, the system works but is quite unstable ... high temperatures ... probably the bus remained at 33MHz?

which software I can use like cpuz under dos?