Processor:
Someone will know better then me if the motherboard can do 5v, If not you still have the option of a Pentium Overdrive but realistically the only advantage it'll have over a dx2/66 is slightly better load times. It's not like a bunch of more games suddenly become playable, for that you'll need to move to Socket 7 or better (which defeats the purpose)

Memory:
Check the modules for the speed usually like -80 -70 -60 lower is better -50 exists i think but rare. Probably not worth the money to upgrade as you'll only notice in benchmarks not real world performance .

Graphics Card:
EISA is kind of special, as long as it has good compatibility with your dos games then thats all that matters, Personally I don't find worry too much about graphics cards on 486's as it'll be the CPU that's the bottleneck

Sound Card:
Love a AWE32 you can upgrade the memory with 30pin ram up to 32MB (although only 28MB will be recognized)

Storage:
I don't recommend SCSI, Drives are old usually had long service lives in servers and the IDE2CF will outperform it anyway.
Of course if you want to play with SCSI then by all means do it though this whole build is just for fun after all.

Cache will depend on what it's already got

Only thing missing is network card for even easier file transfers, just a 10MB ne2000 compatible card will do

chinny22 wrote on 2022-09-28, 16:42:

Processor: Someone will know better then me if the motherboard can do 5v, If not you still have the option of a Pentium Overdriv […]
Show full quote

Processor:
Someone will know better then me if the motherboard can do 5v, If not you still have the option of a Pentium Overdrive but realistically the only advantage it'll have over a dx2/66 is slightly better load times. It's not like a bunch of more games suddenly become playable, for that you'll need to move to Socket 7 or better (which defeats the purpose)

Memory:
Check the modules for the speed usually like -80 -70 -60 lower is better -50 exists i think but rare. Probably not worth the money to upgrade as you'll only notice in benchmarks not real world performance .

Graphics Card:
EISA is kind of special, as long as it has good compatibility with your dos games then thats all that matters, Personally I don't find worry too much about graphics cards on 486's as it'll be the CPU that's the bottleneck

Sound Card:
Love a AWE32 you can upgrade the memory with 30pin ram up to 32MB (although only 28MB will be recognized)

Storage:
I don't recommend SCSI, Drives are old usually had long service lives in servers and the IDE2CF will outperform it anyway.
Of course if you want to play with SCSI then by all means do it though this whole build is just for fun after all.

Cache will depend on what it's already got

Only thing missing is network card for even easier file transfers, just a 10MB ne2000 compatible card will do

Hi thanks for your thoughts...

Good point on the processor, I will have to check a few benchmarks and understand the real difference.

I guess the graphics card will make a difference only in some games (mostly the ones in SVGA), I'll do some benchmarking when the PC arrives and will revert here.

I want to go for SCSI for authenticity and nostalgia (the HDD spin up sound is a great part of the experience for me), but I get your point on performance (and convenience).

The network card is also a good point. Will see what options I have...

Cheers

chinny22 wrote on 2022-09-28, 16:42:

Memory:
Check the modules for the speed usually like -80 -70 -60 lower is better -50 exists i think but rare. Probably not worth the money to upgrade as you'll only notice in benchmarks not real world performance .

Are these compatible?

Found this which gives upgrade options, does look like a POD is your only CPU upgrade option.
https://ardent-tool.com/media/PS2_MOST/ACRORE … PAQ/2005001.PDF

I'd wait for the PC just to be sure what expansion board it has but your most likely after 72pin ram and the ones you linked are 30pin.
I'd also be careful about ram type, I doubt the PC will support EDO RAM, your probably better off sticking with FPM or Fast Page Ram

You could 2 sticks of that ebay listing in your AWE for a total of 8MB but its a waste even Creative said 80ns is fine as it's only going to affect the time it takes to load a soundfont.

Since this is Deskpro/M means a unusual power supply board is replaceable part not a metal box power supply and *major problem*:

No spares anymore! Yes, I searched everywhere even for broken power supply board for 2 years and finally bagged another Deskpro 4/25s M from Rome, Italy paying lot. It came with a working power supply.

Like I said this is very, important to rebuild the ultra rare power supply with new capacitors and renew solder joints that looks cracked.

And good news is I can use ATX PSU simply rewiring the pinout to Deskpro/M, leaving out all 3.3V wires off. Problem is how to mount the ATX board inside to look stock. Or buy a ATX 20 pin extension cable around 6 inch long.

Here's the detail of pinout I created awhile ago.

UPDATE! Confirmed working great using adapter rewired to Deskpro M pinout PSU using a ATX power supply's and still use ATX connector but you have to move wires around.

This is for Deskpro M series PSU pinout measured on the motherboard's.

*N/C X X pin 1 (one), still unknown purpose and has connection, no voltage.
-5V X X <---------Power Good signal.
GND X X -12V
GND X X GND
GND X X GND
GND X X GND
+5V X X +5V
+5V X X +5V
+5V X X +5V
+5V X X +12V
N/C X X +12V
N/C X X N/C

Cheers, Jason

Thanks for the heads up on the Power Supply. I will check mine as soon as the computer arrives.

Also, can any owner of a similar machine confirm what is the compatible RAM for this machine?

As I understand, the parts sold by Compaq where 72-pin 80ns, up to 8MB per RAM stick.

But I still have the following questions:
- Is it compatible with EDO Ram?
- If I purchase a 72-pin memory stick with higher capacity (i.e. 16MB), will it work?
- Will faster modules work? (60ns or 70ns modules?) - And will the computer be able to operate them at the faster speed?
- Will I be able to just buy a 72-pin, 8MB stick from any brand and it will work? Or do I need to source original parts?
- Will with work with modules with and without parity?

Thanks in advance, any help is much appreciated.

NightShadowPT wrote on 2022-09-30, 10:21:

But I still have the following questions: - Is it compatible with EDO Ram? - If I purchase a 72-pin memory stick with higher cap […]
Show full quote

But I still have the following questions:
- Is it compatible with EDO Ram?
- If I purchase a 72-pin memory stick with higher capacity (i.e. 16MB), will it work?
- Will faster modules work? (60ns or 70ns modules?) - And will the computer be able to operate them at the faster speed?
- Will I be able to just buy a 72-pin, 8MB stick from any brand and it will work? Or do I need to source original parts?
- Will with work with modules with and without parity?

I don't know about your machine specifically, but some of the questions are generally answerable:

Don't expect EDO compatibility. If a chipset wants to make use of "fast page mode" by keeping pages open, and doesn't know about EDO, the RAM drives the data lines for longer time than the chipset expects, which can cause bus conflicts, unless a buffer chip between the RAM and the frontside bus isolates the RAM data pin unless they are in active data transfers.

Don't generally expect sticks of higher capacity to work. You need an extra address pin to make use of 16MB ("single-sided") and 32MB ("double-sided") modules compared to 8MB modules. This extra address pin might be missing on a machine designed for 8MB SIMMs only.

As long as you keep in the same coarse speed region, fast memory modules will generally work. A computer designed for 70ns RAM is very unlikely to fail with 60ns or 50ns RAM. I wouldn't blindly trust 35ns RAM (you got stuff like that on early 3D graphics cards like the Virge/DX) to work, though. Most of the time big-brand computers (like HP, Compaq, IBM) don't have user-configurable memory speed settings, so all modules will be operated at the speed the vendor intended the system to run at.

Generally, all PS/2 SIMMs are alike, you don't need brand parts. But there is one thing to be aware of: There are four pins on the PS/2 connector that are used to detect whether a module is inserted in the slot and if yes, what kind of module. These pins are called "presence detect". The combination of pins grounded tells the BIOS about the capacity and access speed of the module. Brand modules typically support presence detect, whereas no-name modules usually just have four empty solder pads where 0-ohm links could have been added during manufacturing. Of course, you can add the links later, too. If a computer uses "presence detect" to verify the memory modules, it doesn't necessarily support the speed grade reported by the module. There are reports of systems (I don't remember whether it's about computers or laser printers) that refuse to accept 60ns SIMMs even if properly coded, because they don't recognize the "60ns" code. Modifying them to contain the 70ns code makes the system work. Adjusting presence detect codes is possible on nearly all PS/2 SIMMs with hobby-grade soldering equipment and skills.

Given my experience with Compaq systems, parity is most likely required.

Hi everyone,

The machine arrived in perfectly working condition, but what was an upgrade project is quickly transforming into a troubleshooting project 😁

I have spent yesterday most of the day cleaning up the unit and started to configure my MS-DOS with all the required tools.

I could make everything work well (haven't reached the AWE32 yet) and after a few benchmarks the performance was very solid - 10.1 on Player Bench, 24.8fps on Chris Bench and 37 fps on 3D Benchmark.
Ran a few games, including Doom that I could surprisingly run at full screen with acceptable performance and everything seemed to be going well.

Earlier today, something weird happened:

- while creating a disk from one of the softpaks (the one that contained the VESA drivers), the program gave a strange error - something about not finding a file - and aborted. To my surprise, when I tried reading any floppy disk, it was showing as empty.
- Thinking of it as just a temporary fit, I rebooted the PC, but it hang on boot (no video, no sound, nothing)
- Tried a few more times and on a few of the reboots, I got a long and a short beep, followed by the error "101-ROM Error" displayed on screen
- One of the reboots, the memory counter showed up - it finished the memory count, but then just a black screen

I kept trying to reboot, but the result was always one of these...

Not sure exactly what I can do at this point, but any help will be appreciated as always.

Cheers,

Some additional information from my troubleshooting session:

- Tried removing the memory board - same result (sometimes counted the 4MB onboard memory and got stuck, other times the beeps and 101 error)
- Tried removing the video card - Got the beep error of missing graphics card
- Tried removing and reseating the processor board - no change
- Disconnected the HDD and both floppies - same result

- The Power supply seems to be working well - the fan spins and power gets to the components.
- No strange smoke or smell came out of the PC when this happened 😀

Again, happy to hear your thoughts as this was quite unexpected.

The plot thickens...

After an endless loop of reboots that took me nowhere, I tried disconnecting the keyboard and that resulted in a message that the keyboard was missing, to press F1 (gotta love this message).
I connected the keyboard, pressed F1 and the PC booted normally.

Tried the same trick a few more times and nothing... stuck on boot or 101 error.

Gave it a pause and when I came back 1h later, tried booting it and it worked.

Used the opportunity to run the EISA configuration utility, just in case something was corrupted, removed and added a card - saved and... the computer seems to be back to normal.

Already rebooted it 10 times, and seems to be operating normally.

I have no idea what happened, how it got solved, but it makes me nervous as I don't like these weird things I cannot explain. Makes me feel like the problem can come back at any time... 🙁

I will keep you posted of any changes.

NightShadowPT wrote on 2022-10-02, 10:12:

After an endless loop of reboots that took me nowhere, I tried disconnecting the keyboard and that resulted in a message that th […]
Show full quote

After an endless loop of reboots that took me nowhere, I tried disconnecting the keyboard and that resulted in a message that the keyboard was missing, to press F1 (gotta love this message).
I connected the keyboard, pressed F1 and the PC booted normally.

Tried the same trick a few more times and nothing... stuck on boot or 101 error.

Gave it a pause and when I came back 1h later, tried booting it and it worked.

This sounds like the typical symptom of a cracked solder joint or torn PCB trace. It might work perfectly when the machine is cold, but fails to work once the machine warms up because due to thermal expansion, the crack opens.

NightShadowPT wrote on 2022-10-02, 10:12:

Used the opportunity to run the EISA configuration utility, just in case something was corrupted, removed and added a card - saved and... the computer seems to be back to normal.

Already rebooted it 10 times, and seems to be operating normally.

If I'm right about the cracked connection, the mechanical movement of the board caused by removing and adding the card might have made it more reliable...

NightShadowPT wrote on 2022-10-02, 10:12:

I have no idea what happened, how it got solved, but it makes me nervous as I don't like these weird things I cannot explain. Makes me feel like the problem can come back at any time... 🙁

... and indeed, with room temperature changes, the next card change, or just mechanical relaxation over time, the problem might reappear. I hope for you that the actual issue was caused by broken contents of the EISA configuration RAM and it is not a hardware issue, though.

mkarcher wrote on 2022-10-02, 13:14:

... and indeed, with room temperature changes, the next card change, or just mechanical relaxation over time, the problem might reappear. I hope for you that the actual issue was caused by broken contents of the EISA configuration RAM and it is not a hardware issue, though.

Yep, fingers crossed...

Anyway, whatever comes I'll have to handle it. 😀
On with the project...

Does anyone has any recommendation on one of those nice IDE 2 CF Card adaptors that are mounted on a rear bracket? I'd like to make it easier to transfer files into the PC... Floppy Disks are tedious and cumbersome for the larger games.

Thanks

When it comes to processor, how can I check what processors are compatible with my processor board?

It originally came with a 486DX-33 and it now has installed a Cyrix 486DX2-66.

How can I check compatibility with 3.5v processors like the DX4 or 5x86 from Cyrix or AMD?

Thanks

Some more updates:

The computer seems to be coming and going... when it is working, it works for hours without any problem... it seems the issue is only manifesting itself during boot time.

I have also been able to run a full memory test (for a couple of hours) during one of the successful boots and no problems were detected.

Given that the system sometimes looses the EISA configuration, I am now inclined to believe the problem may be the battery inside of the Dallas chip (DS1397) . The computer is 30 y/old... it is to be expected.

The odd, difficult to reproduce behavior seems to be consistent with this theory.

I am trying to figure out good options to replace the Dallas, but until now I have only been able to find CR2012 compatible replacements for other versions of the Dallas chip (the 1287 seems to be very popular).
If I fail to find a better solution, I will try to get new Dallas DS1397 from Ebay (although that may not be the best option because there is no guarantee the battery is still working).

The Deskpro M is a nice machine, I own several of these myself.
The only backdraft is that it uses lots of proprietary parts as many other Compaq machines of that aera.
To your questions.
- The only way to use a DX 4 is an interposer socket that might collide with the memory board. The Compaq engineers did not intend the change of the CPU itself, instead they changed the CPU board.
386 and 486 boards with 4 or 8MB onboard were availiable, even a P60 board was availiable, but unluckily mine is broken.
- The memory board uses PS/2 FPM with parity up to 8MB a stick and up to 64 MB for the whole machine (included the memory on the CPU board), so look for sticks with 3, 9, 10 or 12 chips on each side instead of 2 or 8.
- The /M has (optional) onboard sound called "Compaq business audio" which is only usable under Win3.x and requires a drop out box connected to the small PS/2 like connector on the back.
- The BIOS Setup (run from the EISA configuration diskettes) does not know custom IDE drive geometries, so you are stuck to the small drives availiable at the time of release.
Going SCSI is a good way to overcome this limitations.
Feel free to ask further questions, I will try to answer as best as I can.

eisapc wrote on 2022-10-14, 06:50:

The Deskpro M is a nice machine, I own several of these myself. The only backdraft is that it uses lots of proprietary parts as […]
Show full quote

The Deskpro M is a nice machine, I own several of these myself.
The only backdraft is that it uses lots of proprietary parts as many other Compaq machines of that aera.
To your questions.
- The only way to use a DX 4 is an interposer socket that might collide with the memory board. The Compaq engineers did not intend the change of the CPU itself, instead they changed the CPU board.
386 and 486 boards with 4 or 8MB onboard were availiable, even a P60 board was availiable, but unluckily mine is broken.
- The memory board uses PS/2 FPM with parity up to 8MB a stick and up to 64 MB for the whole machine (included the memory on the CPU board), so look for sticks with 3, 9, 10 or 12 chips on each side instead of 2 or 8.
- The /M has (optional) onboard sound called "Compaq business audio" which is only usable under Win3.x and requires a drop out box connected to the small PS/2 like connector on the back.
- The BIOS Setup (run from the EISA configuration diskettes) does not know custom IDE drive geometries, so you are stuck to the small drives availiable at the time of release.
Going SCSI is a good way to overcome this limitations.
Feel free to ask further questions, I will try to answer as best as I can.

That is some valuable information for my project thanks.

On the topic of the system instability, I have some additional information to share.

I have noticed that:
- my first boot of the day ALWAYS succeeds - without fail.
- my subsequent reboots have a failure rate of 50-80% (with the PC working for around 2-10 minutes)
- If I boot successfully, the system is incredibly stable - never crashing - regardless of the amount of time I have it running (under load or not) - I have tried leaving it on for 6 hours straight and it worked like a charm
- The failure to boot has different intermittent behaviors - sometimes I get the "101-ROM Error", sometimes the monitor just looses sync, sometimes it beeps, sometimes it doesn't

I have been able to replace the RTC with a NOS Dallas chip. Since I have replaced it, I have never lost the configuration again, but unfortunately the system continues to be unstable.

Any further guesses on what I should be looking for? Best guesses for the moment are:

- cracked solder joint somewhere in the system (?)
- Failing Power Supply
- Failing Graphics Card
- Failing Processor / Processor Board

Happy to hear your thoughts.

Never had any Issues like this with one of my systems.
The only one not booting at all was the P60 , but if I remember correct it booted after inserting a 486er CPU board instead

eisapc wrote on 2022-10-26, 10:43:

Never had any Issues like this with one of my systems.
The only one not booting at all was the P60 , but if I remember correct it booted after inserting a 486er CPU board instead

I wouldn't mind buying some spare parts to test it out, but prices in ebay are crazy...

Is there any other place where I can look for this material for more affordable prices?

Hi everyone,

I bring an update to the project and troubleshooting.

On the topic of the system instability, it seems I have found the problem and it was the CPU.
I have procured an Intel 486DX2/66 to replace the Cyrix cx486 DX2 - 66 I had in place and all of a sudden, the system became stable. I've been abusing it for 3 days and it's rock solid.
I never suspected of the CPU because in 30 year of working with PCs, this is the first CPU that has ever failed me, especially in such a weird way.
Well, living and learning.

On the topic of upgrades, here is the current situation:

CPU: Upgraded to an Intel 486DX2/66 - Not much of an upgrade I know, but the system is now stable and I can enjoy the 5% performance improvement over the Cyrix.
Memory: I have bought 64Mb of Ram, but could only install 32Mb. If I try to install more the system will not boot into the Bios/Config for the update and I get stuck. I'll do some more research
SCSI: Installed an Adaptec AHA-2740W to be able to use Wide SCSI peripherals
HDD: Upgraded to a Quantum Grand Prix (4.3GB) SCSI Drive
HDD: Added a IDE2CF with a 4GB CF card to easily exchange operating systems
CD: Plextor UltraPlex32x SCSI

I am now configuring the OS and trying some games, but everything seems to be working properly.

I'll come back when I have more news on the project.

Thanks again for trying to help. This is what makes this community great.

Cheers,