The background...

As a child I remember being taken to my local computer shop where on the shelf they had a big collection of processors on display, some of which were the Pentium Pro models. The prices ranged up to several thousand pounds per CPU. I was amazed some of them could be so expensive and wondered what they offered for the money compared to the standard pentiums at only a few hundred pounds.

Recently I saw a Pentium Pro motherboard for sale and as it's getting quite difficult to find the bits to build one of these nowadays I decided that now (only 18 years late!) would be a good time to start.

The build:

Motherboard:

Tyan S1662 D - Dual Socket 8 'BabyAT'

If you're going to have a Pentium Pro I thought makes sense to double up! This board is a standard BabyAT board and I think it retailed for £485 in ~1997.

Here are the CPU sockets. It's very dusty but as I've run out of air duster at the moment it's going to have to stay like that until I can get some more.

This board takes 72pin SIMM memory. There are 8 slots in total and the board can take up to 1GB of ram.

PCI and ISA Slots

Here is the keyboard connector and AT power connector. You can also see the header for the ps/2 port for the mouse.

VRM slot.

Here are the VRMs. They are both Corsair but slightly different model numbers. I think one might be rated for a higher power but I can't find any details.

Here is the memory I am using. 4x 64MB Edo SIMMS for a total of 256MB. It would have cost £245 for each 64MB SIMM back in 1997!

They are 60ns modules.

I fitted a replacement battery/RTC.

Here is where it fits on the board.

Now the interesting bit, the processors!

I understand Intel initally released models ranging from 150mhz-200mhz with 256KB cache. All the intial models were designed for high end workstations except one. This was an ultra high end chip running at 166mhz with double the cache of the workstation models.

On release the retail price of the 200mhz workstation model was around £1200 whereas the 166mhz 512k cache server version would set you back over £1500 per CPU here in the UK.

With this in mind the 166mhz models were the ones I wanted to start with. Here is a picture.

I also got a 'brand new' sealed 180mhz chip in the original box. It has a case sticker inside I really want to get out but since it's still sealed I think I'm going to leave it as it is, as a very geeky souvenir.

I managed to get some new old stock heatsinks to keep them cool.

I got hold of a AT case and set about installing the board. This was much more difficult than I expected as the board is almost exactly the size of the space in the case. I had to remove the heatsinks and VRMs to be able to squeeze it in at an angle.

Then the moment of truth... Whenever I build a new PC I always wonder if it will fire up first time, but this one using nearly 20 year old components... I had no idea if it would work or if it would blow up. 😀

It works!!

A quick install of Windows NT4 to test everything was working...

and then it was time to err...... upgrade ! I wanted to install the 1MB cache versions.

Tyan had a bios update program you could download from their website. Unfortunately it didn't work however I managed to get hold of a suitable version of the award flash program which I ran from a floppy disk.

It didn't give any indication as to if the flash was successful or not but I left the computer on for quite a while to be safe then power cycled... Luckily the bios updated successfully.

This allowed support for the 1MB 200mhz chips and also added Ultra DMA hard disk support. I am a little confused about this as I didn't think this chipset supports UltraDMA?

I also needed better cooling as the heatsinks I got were fairly small. Socket 8 Heatsinks are difficult to find as they are only used on PPro CPUs. I managed to get some comparatively huge compaq heatsinks designed for semi passive use then added the high power fans from the other heatsinks.

These heatsinks are taller than the standard heatsink and fan put together.

So the processors themselves...

For a size comparison of just how big these chips are, here's a picutre of a 2005 mobile Athlon on the PPro 1MB.

Ready for their new home haha

Fitted!

All working! Boot screen showing 2x 1024KB cache.

I'd read online that the Pentium Pro runs very hot and while using the 166mhz 512k versions I was thinking that it was a little bit of an exaggeration. They were hot but not worse than I expected.

The 1MB versions though... From totally cold even with the fan at full speed it takes literally seconds before you can no longer comfortably touch the heatsinks. Because I'm using a standard desktop case there are no fans for air moment and even with the case side off (definately can't put it on!) it's like a mini oven.

I did have a go at undervolting the processors (which takes 10 jumpers!). There is no display in the bios to tell you the voltage so I used a watt meter on the plug socket instead. Unfortunately the VRMs seem to set a min voltage. You can go over it but not under it.

So that's roughly where I'm up to so far. I used the internet achieve to look up prices and total cost so far in 1997 would be approximately £7048 which allowing for inflation would be around £11,820 !!!

It's not too bad though compared to pre built computers at that time. When IBM and ICL launched their first Pentium Pro servers they started at £15,000 for a single 166mhz 512k processor system and were over £30,000 for a dual 166mhz 512k system.

Apologies if any facts are wrong. Please feel free to correct me 😀 Also I have loads of questions, hopefully it'll be OK if I post them and you guys might be able to help me with the answers?