There are special cache sticks for the Opti Viper chipset that have their own pinout that differs heavily from the regular COAST standard:

("Masse" means Ground in the tables)
For Intel Viper there were async. , flow-through burst and pipeline burst modules available. The ID-pin setup is proprietary also.

As long as you don´t find a "Viper-stick" you will encounter the PSU protection moder issue 🙁

majestyk wrote on 2023-08-08, 06:45:

There are special cache sticks for the Opti Viper chipset that have their own pinout that differs heavily from the regular COAST […]
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There are special cache sticks for the Opti Viper chipset that have their own pinout that differs heavily from the regular COAST standard:

viper_module.JPG
coast_module.JPG
("Masse" means Ground in the tables)
For Intel Viper there were async. , flow-through burst and pipeline burst modules available. The ID-pin setup is proprietary also.

As long as you don´t find a "Viper-stick" you will encounter the PSU protection moder issue 🙁

Both exactly and totally not what I wanted to hear, all at once 😀
Clearly the protection is doing its job and has likely saved the poor old 90s veteran four times so far. So realistically I need to find one of these OPTi specific modules somewhere... I don't rate my chances but at least knowing it's a specific thing narrows it down.

Hello!

I'm also looking for a cache module.

Btw what's the fastest cpu that supports without going the overdrive way?

Regards

Carcenomy wrote on 2023-08-08, 06:00:

Long time reader, first time poster. […]
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Long time reader, first time poster.

I've got a sweetheart little Compaq Presario 7222. It's been in the family since new and over the years I've been splashing it with upgrades as I find them - a faster Pentium, extra VRAM, a Voodoo, an AWE32... but there's something that's always eluded me, some cache for the thing.

This thing is from the MiTAC era of Compaq, the board is a MiTAC/Trigon PL5600G based on an OPTi Viper chipset. There's no cache onboard but it does have a COAST slot which is where the struggle begins.

I have tried three different modules from my collection - one ASUS, one Compaq, one Digital branded, all Pipeline Burst. Nope - if they're fitted, the power supply goes into protection mode. Closer examination of the board reveals a factory-set jumper block for cache mode, permanently set to Async. So I got yet another COAST module which was listed as an Async module and looks similar to the original Compaq part number but once again, if it's fitted, the power supply goes into protection mode.

So either I'm trying all the wrong modules and being a menace to myself and others, or I really need to find the correct Compaq module - Compaq part number 236514-001.

Any early Pentium specialists had much to do with Vipers?

izuokan wrote on 2023-10-28, 14:52:

Hello! […]
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Hello!

I'm also looking for a cache module.

Btw what's the fastest cpu that supports without going the overdrive way?

Regards

I'm assuming you're talking about the maximum CPU the 7222 can take?
Officially per Compaq documentation, Pentium 166 classic. However, the board does have a 3.0x multiplier available so a Pentium 200 classic works fine too.
The PL5600G lacks the split voltage rails for MMX CPUs natively, in theory at least it does have a VRM socket available that could be used to allow MMX CPUs but it's very close to the riser board etc, clearance could be an issue. In my case I bit the bullet and put in a PODPMT66X200 Pentium MMX OverDrive 200 - this computer has been in my life since new so I try lavishing it with all the best things I can 😀

As for cache... oh man it's been an odyssey and not one I've succeeded with so far. I've bought several modules, one even promised it's specifically for a Viper and no dice - the really quick check is look for continuity between the pins either end of the module, if they're connected (ie both ground) it won't work and heaven forbid the old MiTAC power supply's protection doesn't trigger, in big trouble.

At this stage I've concluded that beyond Compaq 236514-001 (which I suspect you've equally concluded no longer exists anywhere) the other modules that were once available that suit are IDT7MPV6217S66M and Cypress CYM74B550/P550A/S550/S551PM66C (async/pipeline/sync/sync512k respectively) and thankfully... the datasheet for the Cypress module is still available.

My skillset isn't nearly good enough to design a new module based on the Cypress datasheet, although it does have details on pinout, block diagrams and module capacities required... it should be enough that an enterprising PCB designer could in theory cobble something up. I might look at it myself at some stage but I know I'd miss something critical.

Good luck on your hunt, if you find a module get two I'll happily buy one from you!

Hello!

Thanks for your response.

I will go for an overdrive.

Have you tried this one? 237716-001 with mitsubishi sticker.

Greetings from Chile

Compaq part numbers are a bit deceptive, sometimes the same part number is applied to meaningfully different components, and other times you get the same exact part with a different number. Most of the things that have Compaq part numbers were standard parts made by other companies that Compaq put their part number on. If you can find the companies that made these cache modules, you may be able to find the same model even if it doesn’t have a Compaq sticker or part number on it. I generally try to find a photo of the original Compaq part, then try to find an identical part even if it lacks the Compaq number or has a different number. Most of the rare Compaq parts I’ve encountered ended up being commonly available once I knew the item to look for by the original manufacturer.

One other option is to look for a motherboard that has the cache already installed. That’s how I ended up with a cache module for my Compaq (although mine is a different model than yours).

Holy hell, do not ever “try” coast sticks without using a Ohm meter to verify at minimum the power/gnd pinout.

You can brick one or both pieces.

If you are wanting maximum upgrade, a 400mhz 66x6 k6-3+ won’t need the cache anyway. And should allow you to max out memory without worrying about max cachable

Just need to get an interposer, and a upgraded bios most likely.

Necroware’s vrm module is an option if the board has a vrm slot.

Looks like it has a footprint for it.

But as far as drop in chips go, k6 233 has a 3.2v core voltage. Should work in a single plane socket pretty well enough. Doesn’t solve cache and memory cache issue though

Sphere478 wrote on 2023-12-20, 07:21:

Holy hell, do not ever “try” coast sticks without using a Ohm meter to verify at minimum the power/gnd pinout.

are they really that non-standard that they don't even have power and ground in a consistent place?

Yes there are several different pinouts.

Re: Zeos motherboard project

I have 4 or 5 COAST sticks and all of them are different pinoutwise, with GND and VCC and other signals all over. Putting one in without verifying power connections is going to result in a disaster.

I've got a fake cache pcchips-m507. How can I find out the pinout for the COAST socket?

Best advice is to find a fine sharpie red, orange and black. And map out the pattern on the socket and the coast for 5v, 3.3v and gnd.

You can look up the chip pinout for a known signal reference on the stick. And just power up the mobo for it.

Do it like a key.

If they match, try it.

izuokan wrote on 2023-12-19, 18:04:

Hello! […]
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Hello!

Thanks for your response.

I will go for an overdrive.

Have you tried this one? 237716-001 with mitsubishi sticker.

Greetings from Chile

The genuine Compaq one I'd tried was this part number. No, it's Intel COAST spec, don't do it - lest your PSU's OCP doesn't trigger and you smoke things.

Sphere478 wrote on 2023-12-20, 07:21:

Holy hell, do not ever “try” coast sticks without using a Ohm meter to verify at minimum the power/gnd pinout. […]
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Holy hell, do not ever “try” coast sticks without using a Ohm meter to verify at minimum the power/gnd pinout.

You can brick one or both pieces.

If you are wanting maximum upgrade, a 400mhz 66x6 k6-3+ won’t need the cache anyway. And should allow you to max out memory without worrying about max cachable

Just need to get an interposer, and a upgraded bios most likely.

Necroware’s vrm module is an option if the board has a vrm slot.

Looks like it has a footprint for it.

Solid advice - alas, I was just being foolhardy when I tried the modules in past... I'd never even considered anyone had engineered non-standard slots, I'd only ever known of the Intel COAST spec. Good thing MiTAC built a good OCP circuit!

Yes there's a footprint for a VRM... it would place the VRM in a pretty tight place once the riser is installed so you'd have to be careful with what cards are fitted. K6-3 would be pretty comical but realistically you'd be hamstringing it something fierce, the old Viper isn't fast and the Trio64V+ is somewhat crippled too.

douglar wrote on 2023-12-20, 19:10:

I've got a fake cache pcchips-m507. How can I find out the pinout for the COAST socket?

Hare is the module that worked in my board:

The CM 161 was made by ECS. There are 3 versions: 256K with one TAG chip, 512K with one TAG chip and 512K with 2 TAG chips. The differences can be seen on the flipside.
All n all the CM 161 is a _very_ versatile cache module.