These 3.3v AMD DX2 chips were a popular budget CPU. Almost as fast as an equivalent Intel CPU but less than half the price.
Once AMD moved to a smaller node size to make DX4 chips, it made sense to be able make DX2 chips with the same silicon.

What motherboard do you have ? I have a Am486DE2-66V8TGC (a later model Am486DX2-66 3.3v) and works perfect on a ECS AL486 VLB board set as DX at 33Mhz and 3.3v.

akimmet wrote on 2024-07-27, 23:21:

These 3.3v AMD DX2 chips were a popular budget CPU. Almost as fast as an equivalent Intel CPU but less than half the price.
Once AMD moved to a smaller node size to make DX4 chips, it made sense to be able make DX2 chips with the same silicon.

It certainly does look more like a DX4 or Am5x86 than a DX2 (smaller golden lid on the back).

Are these 3v AMD DX2 like a nerfed DX4, or it's the same DX2 made with a smaller process?

I wonder, wouldn't it have been cheaper and easier (no need for a VRM) for Acer to buy a 5v part though? Were they still being made?

Horun wrote on 2024-07-28, 02:01:

What motherboard do you have ?

The board is an A1G4, came in an AcerMate 466d. I restored the very poorly treated case a long time ago but never tested it much.

The onboard video simply doesn't work. I couldn't find an answer to that. Maybe some component got broken (capacitor, resistor, transistor, memory chip?) and that's why the previous owner (+20 yers ago) was using it with the trusty HMC ISA video card. It does make the 1 long beep and 3 short ones if the on-board video jumper is closed.

Horun wrote on 2024-07-28, 02:01:

I have a Am486DE2-66V8TGC (a later model Am486DX2-66 3.3v) and works perfect on a ECS AL486 VLB board set as DX at 33Mhz and 3.3v.

Shouldn't it be working automatically at double the bus speed (33x2)? Does it support a 3x multiplier?

My only other AMD DX2 66 is a DXL2 version, from 94. It's a 5v part and looks like it's made with the older process.

I just found this thread and it seems like this CPU can probably do a big overclock. I'll try and see how it goes!
Am486DX2-66@123Mhz!

tauro wrote on 2024-07-28, 02:48:

It certainly does look more like a DX4 or Am5x86 than a DX2 (smaller golden lid on the back).

Yes, it is in a smaller process.

tauro wrote on 2024-07-28, 02:48:

Are these 3v AMD DX2 like a nerfed DX4, or it's the same DX2 made with a smaller process?

nerfed due to marketing purposes but perhaps binned too

tauro wrote on 2024-07-28, 02:48:

I just found this thread and it seems like this CPU can probably do a big overclock. I'll try and see how it goes!
Am486DX2-66@123Mhz!

Yes, they were rated up to 3x 40 MHz = 120 MHz.
You may have luck but you also may face stability problems.
Note that at 66 MHz operation you may not need a heatsink or fan. You may try with headsink and fan with higher frequencies.
For extreme overclocking there were peltier and probably dry ice or LN2 used.

tauro wrote on 2024-07-28, 02:48:

The board is an A1G4, came in an AcerMate 466d.

Ahh. Your's must have the little power daughter board, can you post a picture of it ?
Yes running at 33mhz fsb for 66mhz cpu, it does not need a heatsink if the case is well ventilated.

Disruptor wrote on 2024-07-28, 08:45:

nerfed due to marketing purposes but perhaps binned too Yes, they were rated up to 3x 40 MHz = 120 MHz. You may have luck but yo […]
Show full quote

tauro wrote on 2024-07-28, 02:48:

Are these 3v AMD DX2 like a nerfed DX4, or it's the same DX2 made with a smaller process?

nerfed due to marketing purposes but perhaps binned too
Yes, they were rated up to 3x 40 MHz = 120 MHz.
You may have luck but you also may face stability problems.

Unfortunately this CPU doesn't support the 3x multiplier, so I can't test it. It only works in 2x mode. Maybe that's where the artificial limitation was imposed. That and the 8kb cache.
I tested it on a different board (M921) and it can do 120MHz (60x2), and looks like it might support 133MHz too (66x2) since it posts but the board is very unstable at this frequency.

Horun wrote on 2024-07-28, 12:47:

Ahh. Your's must have the little power daughter board, can you post a picture of it ?
Sure!

I found this Cyrix DX2 80, and I can't determine if this is a 3v or a 5v part. It has one of those cool green heat sinks and I don't want to remove it. Here's some pictures:

This one works at 3.3v but only at 66MHz. If I want 80MHz, I need to set it to 4v. 100MHz doesn't work even at 4v. I haven't tried 5v yet, what do you think? I know these came in 3.45v and in 5v varieties, but what about this one? I wish I knew how to interpret those alphanumeric characters on the back.

tauro wrote on 2024-07-28, 02:48:

I wonder, wouldn't it have been cheaper and easier (no need for a VRM) for Acer to buy a 5v part though? Were they still being made?

Wouldn't the 3.3V be able to run without a fan on the heatsink? That could've been some of the motivation for using that?

tauro wrote on 2024-07-30, 05:56:

Unfortunately this CPU doesn't support the 3x multiplier, so I can't test it. It only works in 2x mode. Maybe that's where the a […]
Show full quote

Disruptor wrote on 2024-07-28, 08:45:

nerfed due to marketing purposes but perhaps binned too Yes, they were rated up to 3x 40 MHz = 120 MHz. You may have luck but yo […]
Show full quote

tauro wrote on 2024-07-28, 02:48:

Are these 3v AMD DX2 like a nerfed DX4, or it's the same DX2 made with a smaller process?

nerfed due to marketing purposes but perhaps binned too
Yes, they were rated up to 3x 40 MHz = 120 MHz.
You may have luck but you also may face stability problems.

Unfortunately this CPU doesn't support the 3x multiplier, so I can't test it. It only works in 2x mode. Maybe that's where the artificial limitation was imposed. That and the 8kb cache.
I tested it on a different board (M921) and it can do 120MHz (60x2), and looks like it might support 133MHz too (66x2) since it posts but the board is very unstable at this frequency.

Horun wrote on 2024-07-28, 12:47:

Ahh. Your's must have the little power daughter board, can you post a picture of it ?
Sure!

The attachment vrm.jpg is no longer available

The attachment vrm.back.jpg is no longer available

I found this Cyrix DX2 80, and I can't determine if this is a 3v or a 5v part. It has one of those cool green heat sinks and I don't want to remove it. Here's some pictures:

The attachment cyrix.cx486.dx2.80.jpg is no longer available

The attachment cyrix.cx486.dx2.80.back.jpg is no longer available

This one works at 3.3v but only at 66MHz. If I want 80MHz, I need to set it to 4v. 100MHz doesn't work even at 4v. I haven't tried 5v yet, what do you think? I know these came in 3.45v and in 5v varieties, but what about this one? I wish I knew how to interpret those alphanumeric characters on the back.

That doesn't look impossible to reproduce 😀

H3nrik V! wrote on 2024-07-30, 06:51:

Wouldn't the 3.3V be able to run without a fan on the heatsink? That could've been some of the motivation for using that?

Did all 5v DX2s require a fan?
Maybe you're right. I'm not sure if producing the VRM would have been more costly than a fan anyway.

I read somewhere that after the lawsuit AMD produced only 3v cpus, but that may be wrong and I can't find the source now.

For the intel 5V DX/2-50, I believe the heatsink/fan was optional. For the DX/2-66, a heatsink OR a fan was required.
From what I remember, the 5V AMD DX/2 ran a bit hotter than the intels, and I would probably use a heatsink on their 50MHz part. Not sure about the Cyrix version.

Have you seen the AMD Am486 DX2-66V16BGC model ?
3v, can take 2x80=160mhz
It is absically an am5x86 but with 2x multiplier instead of 4.
Additional info here.

tauro wrote on 2024-07-30, 05:56:

I found this Cyrix DX2 80, and I can't determine if this is a 3v or a 5v part. It has one of those cool green heat sinks and I d […]
Show full quote

The attachment vrm.jpg is no longer available

The attachment vrm.back.jpg is no longer available

I found this Cyrix DX2 80, and I can't determine if this is a 3v or a 5v part. It has one of those cool green heat sinks and I don't want to remove it. Here's some pictures:

The attachment cyrix.cx486.dx2.80.jpg is no longer available

The attachment cyrix.cx486.dx2.80.back.jpg is no longer available

This one works at 3.3v but only at 66MHz. If I want 80MHz, I need to set it to 4v. 100MHz doesn't work even at 4v. I haven't tried 5v yet, what do you think? I know these came in 3.45v and in 5v varieties, but what about this one? I wish I knew how to interpret those alphanumeric characters on the back.

This is a 5V part. The 3.3V part is the V80.

pshipkov wrote on 2024-07-30, 13:18:

Have you seen the AMD Am486 DX2-66V16BGC model ? 3v, can take 2x80=160mhz It is absically an am5x86 but with 2x multiplier inste […]
Show full quote

Have you seen the AMD Am486 DX2-66V16BGC model ?
3v, can take 2x80=160mhz
It is absically an am5x86 but with 2x multiplier instead of 4.
Additional info here.

Nice! That looks like another binned Am5x86. This time they kept the 16kb cache. Other than that, I suspect my chip would probably do 160MHz if I had a motherboard capable of running an 80MHz bus. It takes 133MHz like a champ but that's as far as my motherboard goes.

Anonymous Coward wrote on 2024-07-30, 13:51:

tauro wrote on 2024-07-30, 05:56:

I found this Cyrix DX2 80, and I can't determine if this is a 3v or a 5v part. It has one of those cool green heat sinks and I d […]
Show full quote

The attachment vrm.jpg is no longer available

The attachment vrm.back.jpg is no longer available

I found this Cyrix DX2 80, and I can't determine if this is a 3v or a 5v part. It has one of those cool green heat sinks and I don't want to remove it. Here's some pictures:

The attachment cyrix.cx486.dx2.80.jpg is no longer available

The attachment cyrix.cx486.dx2.80.back.jpg is no longer available

This one works at 3.3v but only at 66MHz. If I want 80MHz, I need to set it to 4v. 100MHz doesn't work even at 4v. I haven't tried 5v yet, what do you think? I know these came in 3.45v and in 5v varieties, but what about this one? I wish I knew how to interpret those alphanumeric characters on the back.

This is a 5V part. The 3.3V part is the V80.

Thank you for clearing that up. And thank you for all the DX2 facts. I wasn't paying attention to that little v next to the 80. Anyway, why would you say it works fine with 3v @66MHz if this is a 5v part? Online I found some Cyrix DX2 80 rated 4v. Maybe this one is a 4v part? Would you run it at 5v with ease of mind? I wouldn't want to fry it.

tauro wrote on 2024-07-30, 15:19:

Nice! That looks like another binned Am5x86. This time they kept the 16kb cache. Other than that, I suspect my chip would probab […]
Show full quote

pshipkov wrote on 2024-07-30, 13:18:

Have you seen the AMD Am486 DX2-66V16BGC model ? 3v, can take 2x80=160mhz It is absically an am5x86 but with 2x multiplier inste […]
Show full quote

Have you seen the AMD Am486 DX2-66V16BGC model ?
3v, can take 2x80=160mhz
It is absically an am5x86 but with 2x multiplier instead of 4.
Additional info here.

Nice! That looks like another binned Am5x86. This time they kept the 16kb cache. Other than that, I suspect my chip would probably do 160MHz if I had a motherboard capable of running an 80MHz bus. It takes 133MHz like a champ but that's as far as my motherboard goes.

Anonymous Coward wrote on 2024-07-30, 13:51:

tauro wrote on 2024-07-30, 05:56:

I found this Cyrix DX2 80, and I can't determine if this is a 3v or a 5v part. It has one of those cool green heat sinks and I d […]
Show full quote

The attachment vrm.jpg is no longer available

The attachment vrm.back.jpg is no longer available

I found this Cyrix DX2 80, and I can't determine if this is a 3v or a 5v part. It has one of those cool green heat sinks and I don't want to remove it. Here's some pictures:

The attachment cyrix.cx486.dx2.80.jpg is no longer available

The attachment cyrix.cx486.dx2.80.back.jpg is no longer available

This one works at 3.3v but only at 66MHz. If I want 80MHz, I need to set it to 4v. 100MHz doesn't work even at 4v. I haven't tried 5v yet, what do you think? I know these came in 3.45v and in 5v varieties, but what about this one? I wish I knew how to interpret those alphanumeric characters on the back.

This is a 5V part. The 3.3V part is the V80.

Thank you for clearing that up. And thank you for all the DX2 facts. I wasn't paying attention to that little v next to the 80. Anyway, why would you say it works fine with 3v @66MHz if this is a 5v part? Online I found some Cyrix DX2 80 rated 4v. Maybe this one is a 4v part? Would you run it at 5v with ease of mind? I wouldn't want to fry it.

It wasn’t unheard of for 5 volt chips to work fine at a lower voltage.

If yours does and is rock solid be happy with it saving some power making less heat.

It isn’t a DV series chip so it must be a 5 volt unit

No idea if that Cyrix DX2-80 will work at 3.3V if you underclock it. Trying it shouldn't hurt the chip.
Cyrix definitely did make CPUs designed for 4V operation, but normally if a CPU doesn't work at standard 5V it will be indicated somehow. Apparently at least some of the V80s are designed to operate at 4V. I've seen it silkscreened onto the CPU. However, as yours is just an "80" it is a 5V part.

rmay635703 wrote on 2024-07-30, 16:57:

It wasn’t unheard of for 5 volt chips to work fine at a lower voltage.

I wasn't aware of that!

So this is the final verdict for this Cyrix DX2 80:

3v - 66MHz - works fine
4v- 80MHz - works fine
5v-100MHz - posts but doesn't boot (unfortunately). I would like to try with 5.3v or a little more voltage but unfortunately that's not a possibility. I tried all my other 5v DX2s (mostly Intel) and this is the only one that posts @100MHz.

So, I suppose this chip is particularly good for a 5v part, working at the rated frequency but at a lower voltage. Maybe it was made with a smaller process.

If you have pot adjustments inside your AT power supply you can crank it up to 5.3 volts.

Cyrix chips were usually close to the edge on stability and your motherboard/cache/expansion cards may not work at 50mhz FSB .

You would need a cpu that is rock solid at 50mhz FSB and then test your system at that clock, my Micronics VLB boards were not stable at 50mhz, I believe in my case it was cache.

rmay635703 wrote on 2024-08-01, 14:46:

Cyrix chips were usually close to the edge on stability and your motherboard/cache/expansion cards may not work at 50mhz FSB .

This particular chip does outstandingly well! Working at 4v when it's a 5v part.

rmay635703 wrote on 2024-08-01, 14:46:

You would need a cpu that is rock solid at 50mhz FSB and then test your system at that clock, my Micronics VLB boards were not stable at 50mhz, I believe in my case it was cache.

Oh yeah, the motherboard I use for testing is a small PC-Chips M921, with the UMC8881 chipset. It's like an M919 but without VLB (and without the fake cache™️).
It's rock solid at 50MHz and it can do 60MHz reliably. It even does 66MHz but it's quite complex and it's not stable.

rmay635703 wrote on 2024-08-01, 14:46:

If you have pot adjustments inside your AT power supply you can crank it up to 5.3 volts.

I tried disabling both caches and it didn't help. At the moment I don't want to get inside the PSU, but maybe in the future... Probably somebody else already did it, with special cooling and such.