Thanks! I'm excited to be back on track with this build.

Capacitor Shopping List
Next-level OR840 badassery (namely, stable operation with up to 2GB RAM) can be achieved through a derivative of this parts list. My mission was to try to extend the life of this board as long as possible, and exceed the ESR/ripple rating for the components that were originally installed.

• Nichicon RR50J821MDN1 6.3V 820uF, qty 12, replaces Sanyo OSCON 4SP820M
• United Chemi-Con APSC100ELL391MHB5S 10V 390uF, qty 4, replaces Sanyo OSCON 10SP270M (see note)
• United Chemi-Con APSG200ELL121MF05S 20V 120uF, qty 1, replaces electrolytic at grid H6
• Nichicon RNS1D220MDS1 20V 22uF, qty 1, replaces electrolytic at grid J9

The surface-mount caps in the audio circuit were well within tolerance and not replaced. Same story for the array of tantalums.

Note: the 8mm diameter OSCONs seem to differ between board revisions - you'll see 470uF caps on other boards. 10V/390uF as an upgrade over the original 10V/270uF units seems to be fine on my early rev board.

Meanwhile...
Configuring SCSI devices..just like riding a bike, right? Seemingly I haven't forgotten how to get drives to play nicely with one another. I did always really like the Adaptec cards.

On channel A/50-pin:

• dual Plextor PX-W124TSi
• Plextor PX-40TSi

On channel B/68-pin Ultra160:

• dual Seagate ST318451LW 18GB 15K screamers

..the Dream Machine called for a 75GB deathstar on the IDE bus, which I somehow have a still-working example. I do want to add a larger capacity drive - I'm thinking perhaps just piling onto the SCSI card with a monster 300GB disk.

A 300 gig SCSI drive sounds like a great idea to me. And I'd be Leary of using the death Star just in case it decides to die on you.

Sadly, SCSI has fallen out of favor with me. It is still cool as hell, but SATA is superior in EVERY measurable way. The only thing scsi has going for it, is the "cool factor" and possibility of some odd-devices. (eg scanner, tape)

luckybob wrote:

...but SATA is superior in EVERY measurable way...

This. And even non-measurable ones like convenience.

I get the coolness factor of SCSI and the hit of nostalgia it provides, but I prefer a fast, reliable and silent solution like an SSD.

yep. There are only 2 reasons I will even consider SCSI.

1. I have no viable alternative. 68k macs and IBM ps/2 machines are notable examples.
2. I want to wave my dick around.

I agree with both of you. This project fits solidly into your reason #2, luckybob. I'm recreating Maximum PC's Dream Machine, it called for SCSI, so there ya go, commence the waving.

For other builds, I've cared not at all for period correctness or whatever - give me every modern convenience I can get; I usually go with a ~120GB SATA SSD.
It was super difficult to track down the 18GB U160 drives, and the 68-pin -LW models (as opposed to the server backplane style LCA drives) were 2x-3x as expensive. Trust me when I say I have absolutely no reason to do SCSI ever again.

(let's not even talk about the cost of this stack of Plextor drives. but they are pretty badass.)

luckybob wrote:

yep. There are only 2 reasons I will even consider SCSI.

1. I have no viable alternative. 68k macs and IBM ps/2 machines are notable examples.
2. I want to wave my dick around.

The way it's meant to be waved(TM).

I never had SCSI back then and due to people ridding themselves of "trash" I got ahold of some controllers and a few disks... pretty awesome seeing/hearing it in action on an older system.

Is it possible to recreate your setup with the compaq ap550 varaint of the or840?

Arctic wrote:

Is it possible to recreate your setup with the compaq ap550 varaint of the or840?

It should be possible. Either with the mods I used or with N-Yagi's mods.

If you have korean modded Tualatins from ebay, you might as well just try those in MSI slotkets, they may work right away (after you've modded the slotkets for dual CPUs, obviously).

I have Upgradeware Slot-T adapters, would they work too? Or would I have to mod them?

edit: Damn I just learned that the AP550 version has a modified/non-standard ATX connector. I need to find the pinout and make an adapter before I can even power it on, since I dont have an original Compaq PSU.

Arctic wrote:

I have Upgradeware Slot-T adapters, would they work too? Or would I have to mod them?

edit: Damn I just learned that the AP550 version has a modified/non-standard ATX connector. I need to find the pinout and make an adapter before I can even power it on, since I dont have an original Compaq PSU.

I don't know if you would have to mod them, I've never had my hands on those adapters to try out or examine. If you're really serious about it and actually start work on it, i.e. get the motherboard running for starters, shoot me a PM and I might be able to help out.

EDIT: Sorry for the bluntness. A few people have contacted me with similar questions and even though I've put considerable effort into helping them, I've yet to see another attempt at Tualatins on i840. I won't get bamboozled into examining another set of slotkets before I know the project will actually go somewhere.

I am trying to figure out if it would be possible with the board that I have. If so, then I would have to buy a VRM and another Tualatin. To get the board running at all I need the original 375W Compaq PSU (or the pinout of the ATX so I can make an adapter).

Arctic wrote:

I am trying to figure out if it would be possible with the board that I have. If so, then I would have to buy a VRM and another Tualatin. To get the board running at all I need the original 375W Compaq PSU (or the pinout of the ATX so I can make an adapter).

WTX:
http://pinouts.ru/Power/wtxmain_pinout.shtml

Remember that original CPQ AP550 PSU has non-atx dimensions, it's larger.
https://www.ebay.com/itm/128399-001-Compaq-AP … D-/232196919714

Raising the topic.
I replicated the build using Compaq AP550 board (customized OR840 with slightly different layout), MS-6905 Master slockets and pair of Tuallies.Applied mods mentioned earlier in this topic and board worked nicely. Complained about missing microcodes during POST and therefore requiring to strike F1 for boot but otherwise without any drama. L2 cache etc is reported properly, works perfectly.
Will do some tests next week.

BTW, I first tested the board with pair of S370-DL slockets that were equipped with 1.4GHz P3-S+korean adapters (I bought just adapters few years ago), that pair was working nicely in my P2B-D, but AP550 did not POST with them.
N-Yagi's site mentiones that S370-DL is unsuitable for this board and only MS-6905 Master is ok.

I have one of these boards from an IBM intellistation for about 15 years or so. Lately I consider rebuilding it, but I notice a noise coming from it when video mode change or when scrolling web page. It sounds almost like a coil whine. I tried 3 differnt GPU, single and dual CPU, doesn't seem to be what its causing. I wonder if recapping the board would change that.

tried putting my ear to it and can't say for certain which component it is.

It will make this kind of noise like in between bios initialization stages like when the monitor will change modes as you are going through the boot process.

does this sound like recapping would solve it?

Did you try different PSU?

Paadam wrote:

Raising the topic. I replicated the build using Compaq AP550 board (customized OR840 with slightly different layout), MS-6905 Ma […]
Show full quote

Raising the topic.
I replicated the build using Compaq AP550 board (customized OR840 with slightly different layout), MS-6905 Master slockets and pair of Tuallies.Applied mods mentioned earlier in this topic and board worked nicely. Complained about missing microcodes during POST and therefore requiring to strike F1 for boot but otherwise without any drama. L2 cache etc is reported properly, works perfectly.
Will do some tests next week.

BTW, I first tested the board with pair of S370-DL slockets that were equipped with 1.4GHz P3-S+korean adapters (I bought just adapters few years ago), that pair was working nicely in my P2B-D, but AP550 did not POST with them.
N-Yagi's site mentiones that S370-DL is unsuitable for this board and only MS-6905 Master is ok.

Happy to hear this, congrats on the successful mod!

Welcome to the club! 😎

Paadam wrote:

Did you try different PSU?

after i change power supply and wash it, it's good now. I'm searching for a pair of massive passive cpu heat sinks. Bcuz fan noise is overthe top.

Obviously High end

Compaq AP550 has onboard Adaptec SCSI, LAN and audio, forgot to mention that earlier.

Nice Intellistation system!!!