Sorry, for the necro.

So I left this machine in storage for about a year I thought I'd dig it out again and see if it's still doing the same.

Upon booting, my fears were correct, still the same. Sometimes getting stuck counting RAM on posting and sometimes the Party Check 2 error.

Since then though, I thought I'd try a few more steps. Reseated the Overdrive CPU, cleaned the edge connector and still no change.

One thing I didn't have to hand at the time is another 5-Volt CPU, and have since found an ST one (from God knows where)! A DX2 @ 66MHz to be precise (ideal as it should be a straight swap, no jumpers to change).

Plugged that in and straight away, it saw all 4096K (on board) and booted to the usual Compaq F-key BIOS error screen (flat CMOS).

'Excellent!' I thought, though this raises a question, why doesn't it like my Overdrive anymore? It was working flawlessly for a few years with it installed. Even when I started to get these posting issues it was a gradual process to it's failure to complete posting.

I'm a little worried that the CPU may be going bad. I really hope not as every time I look on eBay they seem to go for silly money now.

I did swap them back and got the Overdrive to see the 4096KB and boot to the Compaq BIOS but every other time thereafter it was exhibiting the same behaviour. Probably just lucky.

I can't make any sense of it, but the DX2 posts about 80-90% of the time (which is good enough for me). Just a shame as I will miss the extra oomph from the Overdrive.

I wish I could try other CPU's but all the rest are 3-3.45 Volts and I really don't want to risk burning them out. ):

If anyone can share their thoughts on this phenomena, please do let me know as I'm pretty lost to why this is behaving like this.

I really am at my wits end with these AIO Compaq's now...

So an update, a few months ago, I finally splashed out a 3-figure sum on a whole new working machine (bar the HD). Installed a 630MB HD I had laying around, put the original software (including that annoying HD loaded BIOS Compaq insisted on using) on it, and after finally configuring it and installed MS-DOS, play around with a few software settings I reboot to a flashing cursor. Soft reset didn't work so just did a power cycle and, black screen.

Unplug everything unnecessary (HD, daughter card, modem, RAM, etc), still the same. Clean and reseat the edge connector eleventy billion times. Black screen. Swapped CPUs (both Overdrive DX4 and ST DX2 known working), black screen. Play with some of the jumpers, you guessed it, black screen.

Swapped out the other board that displays the RAM counting (and reboots over and over), it still displays that fine (so I know it's a motherboard issue).

So now I have two buggered motherboards for this. And two huge paperweights.

I can see why nobody replied to this topic...

Not sure what I'm going to do with them but I doubt il keep them as they take up so much space.

Anyone else interested in these my honest opinion; don't waste your time or money. They seem to be going up for crazy prices all of a sudden, and frankly from my experience, they're nothing but trouble. Stuck to the desktops and more conventional systems.

I've got a CDS524 and the on board ram isn't recognized and it wont run a true 32bit OS such as linux or OS/2. Runs Dos and Windows 3.1 fine though. Also have the P75 variant and that is fine.
These are good systems if if you have a good one and you are tight on space. Paid $50 for the 486 and $30 for the P75. NZ$ that is,

I used to work on these in high school. The art classes used them. They were reliability disasters.

Most died of heat issues.

Caluser2000 wrote on 2020-01-17, 19:58:

I've got a CDS524 and the on board ram isn't recognized and it wont run a true 32bit OS such as linux or OS/2. Runs Dos and Windows 3.1 fine though. Also have the P75 variant and that is fine.
These are good systems if if you have a good one and you are tight on space. Paid $50 for the 486 and $30 for the P75. NZ$ that is,

I have both a 522 and 524. Both were good, when they worked. I'm sick and tired of them dying on me and p*ssing money away (usually when I feel I'm finally starting to make progress with them). I wouldn't mind so much if there was support for these in the community but barely anyone seems to own them here or the ones that do, I can only assume haven't had such issues and thus probably why there are no responses to this thread (until now).

I wouldn't even know where to look in terms of repair since they're so obscure.

There's a whole thread on vogons about these Compaq systems if you bother to look. Describes how they come to bits and a bit more. They are old systems so with anything that old expect issues occurring.

The Thread in question. There's even a pdf link to the scematic of the 254 board. Compaq cds 524 - upgrade info [help].

Caluser2000 wrote on 2020-01-17, 23:06:

There's a whole thread on vogons about these Compaq systems if you bother to look. Describes how they come to bits and a bit more. They are old systems so with anything that old expect issues occurring.

I see that now, I'm not really regular here so yes I didn't know about the thread originally, not did I think to do a search. I'm sure I did one before but obviously didn't see it when I started this thread before. Perhaps the search system has been improved, or more likely I didn't use the right keywords.

Anyway, I digress. As for what you linked me to, as nice and interesting as it is, doesn't exactly help my issue as it's just a thread of everyone else's machines that seem to be working fine (for them). Nobody is experiencing any hardware issues. Certainly nothing I'm experiencing with my now two fubarred motherboards.

I suspect that with the original board, it's probably an onboard RAM issue. It still does exactly the same now. If you're lucky (and the planets aline and thus) when it manages to count all 4096K onboard, it just throws the
same Parity Check 2 error.

I noticed some speaking of the possibility of disabling onboard RAM, but as far as I can tell, there doesn't seem to be a way. Pity, as that would really tell me if that really is the issue.

No idea of you could just desolder them all and have it will still work.

Yes, I get they're old, but literally none of my other machines have had this level of unreliability. I got a bunch of way older machines that are more complex and stored in way worse conditions and never have a single issue with them.

I know I’m a bit late to the party, so sorry if you already threw the PCs away or something.

Could also be a PSU problem. Have you checked if the voltages are correct and stable?