Please show photos of memory modules. 8MB modules are the max capacity, not 16MB, Those 8MB parity modules are the maximum capacity.

Second, make sure your that these modules are parity. Also has presence detection jumpers on each module which are either solder blobs or soldered zero resistors that leads to the last 4 pins on the SIMM module. For this PC can use 80ns or 70ns.

Third, make sure they are actually FPM not EDO, which this deskpro/M only supported FPM.

Cheers,

why not - cacheable area
arent Deskpro M the ones with weird proprietary chipsets and cpu/ram on external cards?

rasz_pl wrote on 2023-07-26, 02:19:

why not - cacheable area
arent Deskpro M the ones with weird proprietary chipsets and cpu/ram on external cards?

The cachable memory range is not the factor. The Deskpro/M is built like this way with fullest configuration in mind from the start. This design is a processor card means you can choose any processor cards: 386DX with 16K cache, or 486 with no cache, or have a 486 with 256K (8 cache chips and one tag IC). The processor cards have initial memory of either 4MB or 8MB soldered. One put in a 8 slot 72 pin memory expansion card next to this processor card and can populate anywhere from 1 up to 8 parity SIMMs either 1MB, 2MB or 8MB in capacity to hit maximum 64MB. These takes 80ns but will accept 70ns SIMMs.

Contrast this to generic motherboards that sports either 30pin 4 or 8 slots memory and if need more, need to purchase a proprietary memory card as well. At that time back in the day, if you wanted to have it, you have to buy generic motherboard and the expansion memory card at same time. That is significant expense hence very difficult to find now. Nearly all of clone motherboards that has that slot is missing the expansion card and to find one is extremely hard these days if one wanted nowdays.

With Compaq, I was able to find expansion cards easily all the time for both of my M and Deskpro 386e 25. True for many other brands like HP, IBM etc.

PS, finding a generic ISA motherboards with 30pin x 16 slots is also extremely rare. Most are usually 4 or 8 30pin slots are common. Finding a generic 386 or 486 boards with 4 72pin slots is not easy. Mostly had 30 pins with two 72 pin slots. Not many had four 72pin. This changed with quality VLB and Pentium boards now sport 4 x 72pin slots later on especially after 1994 or so while 486 usually cheap ones stayed at 72pin x 2 slots.

Cheers,

pentiumspeed wrote on 2023-07-25, 23:28:

Please show photos of memory modules. 8MB modules are the max capacity, not 16MB, Those 8MB parity modules are the maximum capacity.

They are 8Mb modules. I'll take some pictures when I get home later today.

pentiumspeed wrote on 2023-07-25, 23:28:

Second, make sure your that these modules are parity. Also has presence detection jumpers on each module which are either solder blobs or soldered zero resistors that leads to the last 4 pins on the SIMM module. For this PC can use 80ns or 70ns.

Third, make sure they are actually FPM not EDO, which this deskpro/M only supported FPM.

Hi,

Modules are FPM, have parity and are 70ns.

I have tried swapping the modules in the PC with these ones (take out the 32Mb that work, swap them with these 32Mb) and they work flawlessly.
That's why I don't think the problem is with the modules. The issue only manifests when I'm trying to go over 32Mb.

Would it be possible to update the bios? I know these machines don't really use a Bios in the conventional sense (they have the softpaks), but still, the whole thing is still a bit of a mystery to me 😉

pentiumspeed wrote on 2023-07-26, 02:46:

The Deskpro/M is built like this way with fullest configuration in mind from the start. This design is a processor card means you can choose any processor cards: 386DX with 16K cache, or 486 with no cache, or have a 486 with 256K (8 cache chips and one tag IC).

This is interesting... I though the Compaq Deskpro M series did not have cache... what is the quickest way for me to identify if mine has cache?

I know my processor board part number is 129127-001 (produced in 1992), but could not find any information regarding the cache online.

NightShadowPT wrote on 2023-07-26, 10:30:

pentiumspeed wrote on 2023-07-26, 02:46:

The Deskpro/M is built like this way with fullest configuration in mind from the start. This design is a processor card means you can choose any processor cards: 386DX with 16K cache, or 486 with no cache, or have a 486 with 256K (8 cache chips and one tag IC).

This is interesting... I though the Compaq Deskpro M series did not have cache... what is the quickest way for me to identify if mine has cache?

I know my processor board part number is 129127-001 (produced in 1992), but could not find any information regarding the cache online.

That seems to have started life as a 486DX/33 board...maybe your options are limited by this - https://web.archive.org/web/19961226053450/ht … olume1/dpm.html

Yours is an no external cache. Yet, 486 does have the internal 8K cache and still will take 64MB. Also there are caveats, this why I asked for photos of your modules.

Go on, post these memory modules pictures.

This is very good seller, I can vouch for him. I bought many parts from this seller before. This 486 processor board have 256K cache and 8MB included, so you can know what to look for.

https://www.ebay.com/itm/142744549653?hash=it … ABk9SR-yvsbyyYg

Cheers,

pentiumspeed wrote on 2023-07-26, 19:54:

Yours is an no external cache. Yet, 486 does have the internal 8K cache and still will take 64MB. Also there are caveats, this why I asked for photos of your modules.

How do you know this module does not have extrernal cache? (I'm asking because I'd like to learn how to identify them myself)

pentiumspeed wrote on 2023-07-26, 19:54:

Go on, post these memory modules pictures.

I have attached a photo.

pentiumspeed wrote on 2023-07-26, 19:54:

This is very good seller, I can vouch for him. I bought many parts from this seller before. This 486 processor board have 256K cache and 8MB included, so you can know what to look for.

I wouldn't mind purchasing a new board with Cache, but this one is for a 486DX50, and I need a board that supports a 486DX66. Do you know the part number of a compatible board that comes with Cache? Would THIS ONE have cache?

Also, what is the kind of performance improvement that I can expect from a board with cache?

Cheers,

Left two is 8MB parity, and are compatible.

Top right one SIMM is 4MB parity and is compatible with compaq. These 4MB modules tend to be installed last, but for now hold in reserve as you have 8MB modules.

Middle right are two both kingston are 4MB parity and is compatible with Compaq.

Right, Bottom two are 8MB modules parity as well.

Have you tried to install all 8MB first in slot A, B, C, and D?

All these modules are FPM (fast page mode).

The cached processor board is same as 33MHz model, shares same chips. All you do is change the oscillator IC plastic 5V for either plastic or TTL 8 pin size metal with pins bent out as SMD that is 66.66MHz and different 5V 486DX2 66 processor.

The processor board in green does not have cache. For now get the 50MHz cached board then modify it once you know this works, it is now difficult to find these days. So get what you can get and modify.

Cached processor cards and motherboards with external cache have significant boost in performance. Might not show much if you are using ISA video card, any others can chime in. But I know this cache is very helpful.

Cheers,

pentiumspeed wrote on 2023-07-27, 23:59:

Have you tried to install all 8MB first in slot A, B, C, and D?

Yep. Using 4 x 8MB ends up giving me 36MB Total (4MB from the processor board + 32MB from the expansion board), and it works great.

The problem is when I try to install more of it.
I have taken picture of the additional 8MB modules I am trying to add, they are below.
I have also attached a picture of the Memory expansion board.

To be clearer on what happens if I go over the 32MB in the expansion board:

- PC boots
- Counts memory and only goes up to 36864 KB
- Gives the following message: "164 - Memory Size Error - Run System Configuration Utility".
- Additionally, my SCSI card also throw a message saying "Host Adapter configuration error - BIOS not installed"
- When I put in the Compaq Configuration disk and press F1, the disk starts reading and immediately stops ... and nothing else happens, it's just stuck there.

I am also attaching a photo with the error on boot for good measure 😉

----------------------------------
For the record, I tried installing the memory sticks on the following slots:

Slots A, B, C, D - Total 32MB (+4MB from processor board) - Works
Slots A, B, C, D, E, F, G, H - Total 64MB (+4MB from processor board) - Does not work
Slots A, B, C, D, E, F, G, H - Total 60MB (+4MB from processor board) - Does not work (used 1x 4MB stick for this configuration in case the Maximum accepted by the system would be 64MB total)
Slots A, B, C, D, E, F - Total 48MB (+4MB from processor board) - Does not work
Slots A, B, C, D, G, H - Total 48MB (+4MB from processor board) - Does not work

As long as I don't exceed the 32MB on the memory expansion board, all of the memory sticks work (I have tried rotating them all one by one).

Note: I will open another thread to discuss the Cache/Processor board as it is something I am very much interested in.

----------------

Happy to hear any ideas on how to continue troubleshooting this.

Cheers

You didn't tell me which is which that you have problems with. Please take another picture of these 4 flipped over so I can see the detection presence jumpers.

Now, try first 4 x 8MB in A, B, C, D and other 4 x 4MB in E, F, G, H?

If not, keep trying. But first 4 is 8MB modules, and one 4MB module in slot E. Keep swapping all the modules in E one by one to make sure modules are fine.

First 4 is 8MB modules, and 4MB module in slot E, F. Then E, F, G. Then E, F, G, H.

This is troubleshooting.

I remember having problems during configuration while a HDD was attached.
Try to detach the HDD and run configuration from diskettes, attach HDD again after successful configuration.
Just give it a try.
I was never able to configure one of my /Ms from the setup utility installed on the HDD and my 5+ /Ms all have the full 64MB installed.

Also, I was planning to go 64MB on one of my two M's, at this moment, I have 32MB installed, need to procure four more 32MB SIMMs.

Cheers,

eisapc wrote on 2023-08-03, 12:41:

I remember having problems during configuration while a HDD was attached.
Try to detach the HDD and run configuration from diskettes, attach HDD again after successful configuration.

THAT WAS IT!!

I have disconnected the drive, was able to install the ram without any problems.
Wow... this was a weird one.

Thanks eisapc. Much appreciated.

Also, thanks everyone else for trying to help on this topic.

This is bizarre 😮

Nice to hear my hint was helpful to you, and might be helpful to others in future.
I allways wondered why nobody else experienced the problem, but if no one else extended the memory to the full 64 MB.