That's odd. When I think about it though, I don't think I've ever actually installed a full 2GB on either of my 440GX machines. I've taken them to 1.75GB but I think that was the farthest I went.

"True" PC100 would only mean it has an entry in the SPD file that describes PC100 timings. The RAM chips aren't really any different, they're just different speed grades.
SPD can list up to 3 sets of timings if I remember correctly. The vast majority of PC133 modules also have a PC100 entry programmed, but it could have been omitted if they were specifically intended for some prebuilt brand name system that was known to run at PC133 speed only.
If that was the problem though, then it seems you'd get the same complaint regardless of how many of them were installed.

Do these modules all appear to be the same? All I can think of is maybe the BIOS has some quirky limitation in how it processes all the different SPDs (if they are different) and breaks with that combination for some reason. I'm really grasping at straws there.

Too much load on the memory controller is the likely problem here.

I've had MANY issues with pc133 ram running at 66mhz, but not really at 100mhz.

Are you using OLD double stacked simms? I've literally just tossed those right in the trash because of issues like these.

Attached are photos of the actual sticks of RAM I am using. All IC's have the same model number.

I have run into some some PC133 sticks that were lacking PC100 specs in SPD. For my Dell Precision Workstation 410 (based on 440BX), I recall having to specifically source PC100 CL2 BUFF sticks to get 1 GB working properly.

My hypothesis with the Dell Precision 610 (440GX) is that my sticks of RAM are lacking PC100 CL3 specs, but perhaps have PC100 CL2 specs. So perhaps the 440GX only works with 2 GB when CL3 is used, but can just barely cope with CL2 when 1792 MB is used. Otherwise, perhaps it needs particular IC brands or SPD requirements for 2 GB, or maybe he chipset has deteriorated in time. or maybe 2 GB has never worked on this board. What do you think?

A photo of the motherboard is here: download/file.php?id=91130&mode=view

There are utilities that read spd information.

Can you manually select CL3 and install more ram?

No, there are absolutely no adjustable memory settings in the BIOS.

CPU-Z and Everest will read SPD, but I don't have a harddrive installed on the testbed. I may pull out my SuperMicro dual Tualatin board, install the RAM, and see what the SPD info reads. Unless there are some DOS utilities which read SPD that can fit on a 1.44MB floppy?

Offhand, SPDTOOL.

But I think you need XP.

You can try this DOS version of SPD_Tool v1.2 I got back in early 2000's. The readme is mostly foreign but between it and the Whatsnew.txt it tells which chipsets are supported.
I have used it on many old boards with PC100 and PC133 DIMMS. You may have to put the dimms in a supported board to read them proper. It does work under DOS 6.22 and DOS 7 (Win9x). Got it off my 2002 CD archives of Simtel....

Thanks. I'll try that tool a little later. I just finished pulling out my dual Tualatin based on the ServerWorks HE-SL chipset. For whatever reason, I could not find a version of CPU-Z that works with this motherboard in XP. Thus I used Everest.

Attached are screenshots. The KTD-PE1550/512 modules both support PC133 at CL3 and PC100 at CL2, however the KTM7263/512 modules only support PC100 CL3. This is odd because the PCB revisions for these modules are identical, as are the IC's. Looks like Kingston deliberately gimped their running speeds in SPD.

I do have two other buffered 512 PC133 DIMMs that support PC133 at CL3 and PC100 at CL2, however I still receive the beep codes on the Dell Precision Workstation 610 440GX motherboard when 2 GB is installed. Thus I suspect the issue isn't related to SPD. The BIOS or chipset don't seem to be able to cope with 2 GB. Is there a way to disable this error and force boot anyway?

Do not know of a way to force boot but to me I see four sticks that no not match exactly. Try this: put the PC-100 in the first slot of each bank and the PC-100/133 in next slot. So yes you are mixing ram per bank but the first slot of each bank should be telling the chipset how to run the ram. Just as a test. I see it as you are trying to match ram per bank but in this case you may have to think outside the box 😀 and not think of matching up. Just try it and let us know what happens.

I just tried the RAM as you suggested, however the beep code is still present.

Perhaps someone else with a 440GX board, particularly those with a Dell Precision Workstation 610 M, will chime in.

HMM.

my brain is firing off a red flag. "1 rank, 4 banks"

I know that's a BIG deal with newer server boards. They usually go into great detail about rank limits.

maybe, its running out of available banks and crashes. I know for a fact my XG-DLS runs just fine with 4x 512gb dimms.

if my brain, is braining correctly. the 440GX supports 2gb, in 8 ranks. (4x dual sided dimms).

Do you have any 512mb dimms that are 2-rank? If I'm not crazy, it might like those memory modules better.

Nice theory, but I don't have any other 512 MB BUFFERED SDRAM to test this theory. I have just 6 of these modules in this configuration.

Hmm.. maybe the 512K are to dense per chip and maybe 256k x8 DIMMS would work where 4x 512k do not based on their chips density. As you say maybe double sided 512k (256k per side and less per chip density) is the issue...
How many 256K RDIMMS do you have ?
Added: I gave all my RIMM boards away years ago because I hated that memory as I did the IBM MCA stuff (two failures in the progress of computers, just my opinion)..

Although neither are slot 2 Xeon, I currently have 2 440GX-based slot 1 boards; an Intel L440GX+ and a Supermicro P6DGU. Both will happily max out stably at 2GB, either with 4 x 512MB or 2 x 1GB, although nearly all of my registered SDRAM is PC133R CL3 (I have one set of CL2) in the form of 1GB sticks. As I have quite a few different brands / models / chip configs, I can post some specs & pics if you think it would help.

To clarify, i'm not saying it's a 100% chance that's the issue, but when I read "1 rank" and looked up the 440GX's 8 rank by 256mb maximum, my brain fired off like pee-wee's playhouse when someone says the word of the day.

Ok I Understand Luckybob and PC Hoarder, being not all ram is equal and not all boards work the same. OK feipoa, just for shits and grins have you tried 1 RDIMM in the first slot and then skip a slot and put second in, in both banks ? Sort of like a 4 slot older 486 or Pentium that sometimes you have to skip a slot with some density ram SIMMS...just a thought. Other than that it could be a BIOS issue but am sure you already upped to newest or best.

Edit: according to the Intel docs "Intel® 440GX AGPset Design Guide March 1999":
1.3.2.2 DRAM Interface
The 82443GX integrates a main memory controller that supports a 64/72-bit DRAM interface which operates at 100 MHz. The integrated DRAM controller features: supports up to 4 double-sided DIMMs, 8M to 256M using 16Mbit technology, 1 GB using 64Mbit technology, and 2 GB using 128M or 256M technology, two copies of MAxx are provided for optimized timing, and ECC with hardware scrubbing.

PC Hoarder Patrol wrote on 2020-09-01, 03:36:

Although neither are slot 2 Xeon,
Both will happily max out stably at 2GB, either with 4 x 512MB or 2 x 1GB, although nearly all of my registered SDRAM is PC133R CL3 (I have one set of CL2) in the form of 1GB sticks. As I have quite a few different brands / models / chip configs, I can post some specs & pics if you think it would help.

So maybe feipoa, your DIMMS are not compatible to reach 2GB where PC Hoarder just got lucky or his were more chipset/BIOS compatible or due to not running dual xeon.... just another odd thought.

Support in the bios for 2GB seems to have been there since A-02 and the latest version appears to be A-11. It's clearly model specific, as I've seen one old for sale thread online for a Precision 610 Server Workstation motherboard with dual P3 Xeon 550 and 2GB Ram, interestingly with a DELL-specific Kingston part # KTD-WS610R/512. Can't find a spec sheet for it, but one seller lists it as CL2 2Rx4.

Despite my luck with the GX boards, you do run into these issues trying to max out memory on these old boards - I've a Gigabyte dual Tualatin board which won't even POST with 4GB of any of my CL3 sticks but will survive long enough with a CL2 set to POST then hang immediately after. Less than 4GB (3 or 4 sticks) is peachy though!

Looks like there are a few sellers with online with KTD-WS610R/512, however they are fetching $40 each. Wayyyyyyyyyyy too steep for me. And there is no guarantee they would even work.

I pulled the RAM out of my Dell Precision Workstation 410 (440BX) and they are indeed PC100 CL2 memory. I recall for that board, they must have PC100 entries in SPD for them to work. I tried them in the Dell 610 board and the full 1 GB works. I have some other REG/BUFF DIMMs that are 256 MB, but instead of being 16-chip, they are 8-chip. I installed them into the Dell 610 board and I don't even get beep codes - the screen stays blank. They are PC133 DIMMs that came on a Supermicro dual Tualatin board.

So you are saying that 1 GB DIMMs worked on your 440GX board? I didn't even think to try those but will.