If you want DX2-66, than I guess it's a good one.

Besides engineering samples, SX955 is the only Intel 486 DX2 that supports WB cache. All Intel 486 DX2 are 5 Volt types.

I don't think that's true. Intel made 3.3V DX/2s as well. They shared silicon with the DX/4, even retaining the 2X/3X multiplier selection.

AlessandroB wrote on 2022-05-15, 10:26:

I have one SX807 that is "SL" version but not WB, instead SX955 is "SL" and also WB. So it is the one to have?

Hi AlessandroB,

Just a side note, but I had a recent interesting experience with those two DX2-66 variants. I upgraded a small 486 system board with the SX807 and all worked normally, I then tested out a SX955 variant on the same board and de-turbo mode would hard freeze the system. After a CMOS reset I stuck the SX807 back in and the turbo toggle worked normally again. Now, this might just be a faulty SX955, but if anyone reading this has a setup where they can test this I would be interested to see if they experience the same thing.

Doesn't the WB cache require support from the motherboard? The later 486 boards have that option in the bios, but they also support faster 3.3v processors.
My earlier board that only supports 5v processors does not have that bios option to toggle WB/WT cache.

pixel_workbench wrote on 2022-05-15, 16:06:

Doesn't the WB cache require support from the motherboard? The later 486 boards have that option in the bios, but they also support faster 3.3v processors.
My earlier board that only supports 5v processors does not have that bios option to toggle WB/WT cache.

In my case the motherboard has the WB/WT toggle, but only supports 5V CPUs.

liqmat wrote on 2022-05-15, 15:44:

AlessandroB wrote on 2022-05-15, 10:26:

I have one SX807 that is "SL" version but not WB, instead SX955 is "SL" and also WB. So it is the one to have?

Hi AlessandroB,

Just a side note, but I had a recent interesting experience with those two DX2-66 variants. I upgraded a small 486 system board with the SX807 and all worked normally, I then tested out a SX955 variant on the same board and de-turbo mode would hard freeze the system. After a CMOS reset I stuck the SX807 back in and the turbo toggle worked normally again. Now, this might just be a faulty SX955, but if anyone reading this has a setup where they can test this I would be interested to see if they experience the same thing.

My Sx807 work with the 3,3v regulator plugged-in

To me the SX955 is the ultimate DX2-66.
I've got three of them.

They all do run fine art 3,3v and without fan they keep cool to the touch.
WB does require bios support. If the bios does not explicitly support it, chances are high the CPU runs WT (nothing wrong with that, runs just fine, but a waste of the capability).

Performance is about 5% higher on three boards I have, compared to a regular wt dx2.

waterbeesje wrote on 2022-05-15, 19:06:

To me the SX955 is the ultimate DX2-66. I've got three of them. […]
Show full quote

To me the SX955 is the ultimate DX2-66.
I've got three of them.

They all do run fine art 3,3v and without fan they keep cool to the touch.
WB does require bios support. If the bios does not explicitly support it, chances are high the CPU runs WT (nothing wrong with that, runs just fine, but a waste of the capability).

Performance is about 5% higher on three boards I have, compared to a regular wt dx2.

and what about the “sl” capabilities?

AlessandroB wrote on 2022-05-15, 19:23:

waterbeesje wrote on 2022-05-15, 19:06:

To me the SX955 is the ultimate DX2-66. I've got three of them. […]
Show full quote

To me the SX955 is the ultimate DX2-66.
I've got three of them.

They all do run fine art 3,3v and without fan they keep cool to the touch.
WB does require bios support. If the bios does not explicitly support it, chances are high the CPU runs WT (nothing wrong with that, runs just fine, but a waste of the capability).

Performance is about 5% higher on three boards I have, compared to a regular wt dx2.

and what about the “sl” capabilities?

To be honest, I've never noticed any performance difference for SL and never really dug into it. All I know about SL is it uses some energy optimization but that's about it

waterbeesje wrote on 2022-05-15, 19:06:

To me the SX955 is the ultimate DX2-66. I've got three of them. […]
Show full quote

To me the SX955 is the ultimate DX2-66.
I've got three of them.

They all do run fine art 3,3v and without fan they keep cool to the touch.
WB does require bios support. If the bios does not explicitly support it, chances are high the CPU runs WT (nothing wrong with that, runs just fine, but a waste of the capability).

Performance is about 5% higher on three boards I have, compared to a regular wt dx2.

And do your SX955 CPUs operate normally (slower) with turbo off? I am still testing on the board I have, but in all my years I've never had this particular issue so trying to narrow down the problem.

For that I haven't noticed any weirdness do far, but I haven't tested it purposely.

Old theard, but worth to posting.

But truly best DX2-66 ist a SK080, 3.3V DX2-66 von Intel. No WB-Cache, but it is faster than ordinary DX2

It is a downclocked iDX4 with 2 & 3 Multi (works also with 3x Multi)

Little benchsession with Trio64V+ VLB on MSI 4138

Madao wrote on Yesterday, 16:11:

Old theard, but worth to posting. […]
Show full quote

Old theard, but worth to posting.

But truly best DX2-66 ist a SK080, 3.3V DX2-66 von Intel. No WB-Cache, but it is faster than ordinary DX2

It is a downclocked iDX4 with 2 & 3 Multi (works also with 3x Multi)

Little benchsession with Trio64V+ VLB on MSI 4138

The attachment 66mhz battle.jpg is no longer available

Would be interesting to compare the dx2-66 to the dx4-75

I would almost guess the fastest dx2 would be nearly identical if not a tad faster in certain metrics depending on ram/cache timing

that difference is likely due to hardware imul support added to the dx4 core, pcpbench must be making great use of that instruction.

this is one of those things that is somehow mentioned almost nowhere on the internet, the only source discussing this was a topic on some old programming forum but it's been down for a few years now. otherwise old magazines, but there is a possibility it's mentioned in some old intel spec sheet or programming manual as well.

IIRC mp3 playback is another thing that runs faster beyond expectation even considering the extra cache, so that's something else that might be heavily using imul. i'm not sure if AMD also did this for any of their 486 variants though.