EZ1585CT

The Serpent Rider wrote on 2018-09-17, 15:48:

EZ1585CT

Is there a modern equivalent to this? I'm only finding one seller, on ebay. They have 2 stars for this product as nos, but reviews say they are not working.

Thanks,
TW

Google datasheet. Look for specs and find replacement with identical specs.

The Serpent Rider wrote on 2018-09-17, 21:48:

EZ1585CT

I cannot confirm. Mine has a LT1584 VRM.

This board received several specification updates. Maybe the board received a revision at some point:

https://www.elhvb.com/mobokive/archive/Intel/ … pd_67430116.pdf

Most notably:

Support for 233 MHz Pentium processors with MMX technology is available in PBA revision 669379-304, 680904-302 and higher.

Kahenraz wrote on 2024-03-03, 10:21:

The Serpent Rider wrote on 2018-09-17, 21:48:

EZ1585CT

I cannot confirm. Mine has a LT1584 VRM.

The 1584 and 1585 are just two models in the same family of LDO regulators. They are one component of the VRM.

Lots of reasons they would switch between these two. Different revisions might need to up the amp rating for newer power hungry processors, or just simple market availability.

Speaking of VRMs, I've been wondering how Intel says that it can support the Pentium 233 MMX within spec. I only see a single linear voltage regulator that outputs 3.3V. Does it not have a second regulator for the split voltage?

My board is even labeled as supporting the 233 MMX, which was only shipped with a split voltage.

In fact, it actually supports a "higher" voltage with a jumper:

I found another section in the documentation that talks about this. I confirmed on the Vout pin that when a processor that is detected as "MMX" is used, the output voltage is set to 2.9V. It should be possible to reduce this further by adding a resistor to the ADJ pin on the regulator, I think.

Kahenraz wrote on 2024-03-03, 11:42:

I found another section in the documentation that talks about this. I confirmed on the Vout pin that when a processor that is detected as "MMX" is used, the output voltage is set to 2.9V. It should be possible to reduce this further by adding a resistor to the ADJ pin on the regulator, I think.

VRM.png

Interesting subject, i have the same board (with sticker) running a 200 MMX and have a 233 MMX upgrade available. I still have to look into the changes to get it running. With the sticker on the board you would assume it's safe to install a 233 MMX.

The 200 Mhz MMX will overclock to 233 easily. You have to set the jumpers to select it either way, whether you have the specific processor or not. So, you may as well try it and see if it works. I'm already using a 200 Mhz at 233 Mhz as well.

Kahenraz wrote on 2024-03-03, 11:53:

The 200 Mhz MMX will overclock to 233 easily. You have to set the jumpers to select it either way, whether you have the specific processor or not. So, you may as well try it and see if it works. I'm already using a 200 Mhz at 233 Mhz as well.

Maybe, that's a better solution. But still i wonder why Intel specifies the 233 MMX. Thanks for the tip!

Kahenraz wrote on 2024-03-03, 10:38:

Speaking of VRMs, I've been wondering how Intel says that it can support the Pentium 233 MMX within spec. I only see a single linear voltage regulator that outputs 3.3V. Does it not have a second regulator for the split voltage?

I think I was mistaken. The processor is probably pulling 3.3V from the ATX power supply. This VRM is the regulator for the split voltage.

Kahenraz wrote on 2024-03-03, 11:59:

I think I was mistaken. The processor is probably pulling 3.3V from the ATX power supply. This VRM is the regulator for the split voltage.

No, ATX has allowed simplified design. On Intel 430TX mobos, I/O and memory are powered directly through +3.3v rail and processor is powered through adjustable linear voltage regulator on +5v rail. So there's no need for AT workarounds like split rail - everything except CPU is powered directly from PSU.