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First post, by nwsw

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Hi All,

I have an abit BX-6 Rev 2 motherboard. With the following combinations of ram, the BIOS memory test will show 756MB, but when I boot into the OS (Windows 7) and load CPU-Z it shows as 1024MB of RAM. Which one is incorrect?

All Memory Masters (eBay seller)
PC 133 512MB SDRAM + PC 256 MB SDRAM x2
PC 133 512MB SDRAM x2 + PC 256 MB SDRAM x2

Much appreciated, I didn't see this question in older posts, apologies if it has been posted before.

Reply 3 of 24, by Horun

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nwsw wrote on 2020-08-01, 23:34:

PC 133 512MB SDRAM + PC 256 MB SDRAM x2
PC 133 512MB SDRAM x2 + PC 256 MB SDRAM x2

The top one would be 1GB (1x 512M + 2x 256M), the bottom one would be 1.5Gb (2X 512M + 2X 256M). So which is it ?
The BIOS should show (within reasonable percent) what it sees as true ram. If both above RAM choices show 756Mb then something is wrong with the ram or ram slots or motherboard.

Hate posting a reply and have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. 🤣 Second computer a 286 12Mhz with real IDE drive ! After that came 386, 486, Pentium, P.Pro and everything after....

Reply 4 of 24, by Warlord

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My guess is windows 7 is correct and your bios is wrong. To be sure run memtest 86 from a floppy and see how much memory it can count, and check for errors.

Last edited by Warlord on 2020-08-02, 00:02. Edited 2 times in total.

Reply 5 of 24, by nwsw

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Horun wrote on 2020-08-01, 23:57:
nwsw wrote on 2020-08-01, 23:34:

PC 133 512MB SDRAM + PC 256 MB SDRAM x2
PC 133 512MB SDRAM x2 + PC 256 MB SDRAM x2

The top one would be 1GB (1x 512M + 2x 256M), the bottom one would be 1.5Gb (2X 512M + 2X 256M). So which is it ?
The BIOS should show (within reasonable percent) what it sees as true ram. If both above RAM choices show 756Mb then something is wrong with the ram or ram slots or motherboard.

I tried both permutations. I am running Memtest86 at the moment and I'm seeing errors on tests 3,4,5 so I am going to do some troubleshooting. It shows 1024MB ram for both permutations, probably capped by the BIOS.

Reply 6 of 24, by Warlord

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There are "reasons" historically" why bx has issues with ram over 384mb of ram. while later boards got better issues still persisted. Test sticks in mem test individually.

Most boards have trouble running 512. Very good boards could do 756mb. 4 slot boards are rare. And usually bx will only work with 256 meg modules. 512 meg modules dont work.

Reply 7 of 24, by Horun

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Warlord wrote on 2020-08-02, 00:03:

There are "reasons" historically" why bx has issues with ram over 384mb of ram. while later boards got better issues still persisted. Test sticks in mem test individually.

Agree ! Most could barely run 512MB. The 440BX has a theoretical max of 1Gb but that also depends on the BIOS support, how the southbridge is wired and also if single sided or double sided SIMMS are used.

Hate posting a reply and have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. 🤣 Second computer a 286 12Mhz with real IDE drive ! After that came 386, 486, Pentium, P.Pro and everything after....

Reply 8 of 24, by darry

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nwsw wrote on 2020-08-01, 23:34:
Hi All, […]
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Hi All,

I have an abit BX-6 Rev 2 motherboard. With the following combinations of ram, the BIOS memory test will show 756MB, but when I boot into the OS (Windows 7) and load CPU-Z it shows as 1024MB of RAM. Which one is incorrect?

All Memory Masters (eBay seller)
PC 133 512MB SDRAM + PC 256 MB SDRAM x2
PC 133 512MB SDRAM x2 + PC 256 MB SDRAM x2

Much appreciated, I didn't see this question in older posts, apologies if it has been posted before.

The 440BX chipset only supports a max DIMM size of 256MB . Only 256MB will be usable of a 512MB DIMM . CPU-Z will likely report the total capacity of installed DIMMs regardless of what is actually usable .

PC 133 512MB SDRAM + PC 256 MB SDRAM x2 should yield up to to 768 MB or as little as 512MB (depending on whether 256MB DIMMs are recognized as 128MB or 256MB each, depending on density, 512MB DIMMs will be seen at 256MB each).
PC 133 512MB SDRAM x2 + PC 256 MB SDRAM x2 should yield up to 1024MB or as little as 768MB (depending on whether 256MB DIMMs are recognized as 128MB or 256MB each, depending on density, 512MB DIMMs will be seen at 256MB each).

Reply 10 of 24, by dionb

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darry wrote on 2020-08-02, 00:12:
[...] […]
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[...]

The 440BX chipset only supports a max DIMM size of 256MB . Only 256MB will be usable of a 512MB DIMM . CPU-Z will likely report the total capacity of installed DIMMs regardless of what is actually usable .

PC 133 512MB SDRAM + PC 256 MB SDRAM x2 should yield up to to 768 MB or as little as 512MB (depending on whether 256MB DIMMs are recognized as 128MB or 256MB each, depending on density, 512MB DIMMs will be seen at 256MB each).
PC 133 512MB SDRAM x2 + PC 256 MB SDRAM x2 should yield up to 1024MB or as little as 768MB (depending on whether 256MB DIMMs are recognized as 128MB or 256MB each, depending on density, 512MB DIMMs will be seen at 256MB each).

Exactly.

What concerns me: why is BIOS reporting 756MB not 768MB? Given it's a BX there's no integrated VGA. The 32MB difference is the exact size of the 32Mx8 chips on the 512MB DIMM. Almost sounds like one is bad...

Reply 11 of 24, by nwsw

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dionb wrote on 2020-08-02, 00:27:
darry wrote on 2020-08-02, 00:12:
[...] […]
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[...]

The 440BX chipset only supports a max DIMM size of 256MB . Only 256MB will be usable of a 512MB DIMM . CPU-Z will likely report the total capacity of installed DIMMs regardless of what is actually usable .

PC 133 512MB SDRAM + PC 256 MB SDRAM x2 should yield up to to 768 MB or as little as 512MB (depending on whether 256MB DIMMs are recognized as 128MB or 256MB each, depending on density, 512MB DIMMs will be seen at 256MB each).
PC 133 512MB SDRAM x2 + PC 256 MB SDRAM x2 should yield up to 1024MB or as little as 768MB (depending on whether 256MB DIMMs are recognized as 128MB or 256MB each, depending on density, 512MB DIMMs will be seen at 256MB each).

Exactly.

What concerns me: why is BIOS reporting 756MB not 768MB? Given it's a BX there's no integrated VGA. The 32MB difference is the exact size of the 32Mx8 chips on the 512MB DIMM. Almost sounds like one is bad...

I did a ton of testing using all possible combinations of the following SDRAM that I own in 66/100/133mhz (yes, that many memtests and windows boots):
4x PC 100 256MB SDRAM
4x PC 133 256MB SDRAM
2x PC 133 512MB SDRAM

My main findings:

1. CPU-Z somehow recognizes the full 512MB where the BIOS/memtest86/Windows only recognize 256MB. That answers the main question of the thread.
2. Windows XP/Vista/7 will give an unsupported ACPI error when booting at 133mhz with more than 512MB of physical RAM. ACPI is recognized and has no issues with 512MB RAM or less, additionally with up to 1024MB at 66/10omhz. Installations also blue screen at 133mhz at some point with more than 512MB RAM.
3. All RAM (including 512MB) passes memtest86 at 66/100mhz. My 4x 256MB PC 133 and 2x 512MB 133 will give many test 3 and test 4 errors at 133mhz in all combinations above 512MB ram.
4. I think my PC is stuck in the Gamma Quadrant with a severe lack of dilithium.

At this point I am going to benchmark 933mhz (133mhz clock) with 512 MB PC 133 versus 700 mhz (100mhz clock) with 1024MB PC 100. To the 3dmarks!

Reply 12 of 24, by darry

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nwsw wrote on 2020-08-02, 04:36:
I did a ton of testing using all possible combinations of the following SDRAM that I own in 66/100/133mhz (yes, that many memtes […]
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dionb wrote on 2020-08-02, 00:27:
darry wrote on 2020-08-02, 00:12:
[...] […]
Show full quote

[...]

The 440BX chipset only supports a max DIMM size of 256MB . Only 256MB will be usable of a 512MB DIMM . CPU-Z will likely report the total capacity of installed DIMMs regardless of what is actually usable .

PC 133 512MB SDRAM + PC 256 MB SDRAM x2 should yield up to to 768 MB or as little as 512MB (depending on whether 256MB DIMMs are recognized as 128MB or 256MB each, depending on density, 512MB DIMMs will be seen at 256MB each).
PC 133 512MB SDRAM x2 + PC 256 MB SDRAM x2 should yield up to 1024MB or as little as 768MB (depending on whether 256MB DIMMs are recognized as 128MB or 256MB each, depending on density, 512MB DIMMs will be seen at 256MB each).

Exactly.

What concerns me: why is BIOS reporting 756MB not 768MB? Given it's a BX there's no integrated VGA. The 32MB difference is the exact size of the 32Mx8 chips on the 512MB DIMM. Almost sounds like one is bad...

I did a ton of testing using all possible combinations of the following SDRAM that I own in 66/100/133mhz (yes, that many memtests and windows boots):
4x PC 100 256MB SDRAM
4x PC 133 256MB SDRAM
2x PC 133 512MB SDRAM

My main findings:

1. CPU-Z somehow recognizes the full 512MB where the BIOS/memtest86/Windows only recognize 256MB. That answers the main question of the thread.
2. Windows XP/Vista/7 will give an unsupported ACPI error when booting at 133mhz with more than 512MB of physical RAM. ACPI is recognized and has no issues with 512MB RAM or less, additionally with up to 1024MB at 66/10omhz. Installations also blue screen at 133mhz at some point with more than 512MB RAM.
3. All RAM (including 512MB) passes memtest86 at 66/100mhz. My 4x 256MB PC 133 and 2x 512MB 133 will give many test 3 and test 4 errors at 133mhz in all combinations above 512MB ram.
4. I think my PC is stuck in the Gamma Quadrant with a severe lack of dilithium.

At this point I am going to benchmark 933mhz (133mhz clock) with 512 MB PC 133 versus 700 mhz (100mhz clock) with 1024MB PC 100. To the 3dmarks!

1) CPU-Z is likely just reading the SPD ROM on the DIMMs to identify their capacity . Just in case I did not make it clear enough, it is physically impossible for a 440BX board to use more than 256MB of a 512MB DIMM . No force in the universe can change that, regardless of what CPU-Z says, so there is no point in using 512MB DIMMs anyway (in a 440BX board) if you already have working 256MB DIMMs .

2) and 3) 133MHz is technically overclocked for a 440BX board, so stability issues or constraints may appear when running at that speed . My Asus P3B-F, for example, will not recognize more than 3 of its 4 DIMM sockets when running at that speed, other boards will behave differently . Have you tried with exactly 3x256MB DIMMs at 133MHz FSB and have you tried relaxing memory timings ?

4) Unfortunately, the 440BX was not designed for that high of a warp speed (133MHz). It can usually work anyway but there are compromises/limitations .

IMHO, even if you can't go beyond 512MB total RAM , but everything works stable at 133MHz, I would still call it a success . Running anything above Windows XP and compatible software beyond 2002-ish probably won't be very satisfactory (EDIT : things moved fast back then) anyway on that kind of CPU, so you may actually be able to live with 512MB .

Good luck and keep us informed about how things turn out .

Reply 13 of 24, by nwsw

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Thanks for the great feedback as usual darry! Somehow I missed your first 2 posts, so my apologies. I will let you know how things go, I'm currently benchmarking Asheron's Call with various combinations of CPU/RAM/Clock speed and I'll be sure to share those when done.

Reply 14 of 24, by Warlord

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very few very late 440bx boards had proper AGP/PCI dividers. So if your board doesn't have that, or you don't bother to set it correctly you are effectively overclocking the AGP and PCI bus by running the memory at 133 mhz. poor stability is one thing. Frying expansion cards is another, or frying your board because the cards fry. It's not that 440bx cannot handle 133 mhz, its that majority of the boards don't have dividers, like you see on good Pentium 4 boards.

You need to take into account also the more sticks of ram you slot the more stress that is putting on the VRM.
Like as if most 440bx actually have what in modern times is considered a VRM.
Add a power hungry GPU a fe expansion cards and decide to run your fans off the motherboard headers, it's a recipe for disaster.

Reply 15 of 24, by darry

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Warlord wrote on 2020-08-02, 07:05:
very few very late 440bx boards had proper AGP/PCI dividers. So if your board doesn't have that, or you don't bother to set it […]
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very few very late 440bx boards had proper AGP/PCI dividers. So if your board doesn't have that, or you don't bother to set it correctly you are effectively overclocking the AGP and PCI bus by running the memory at 133 mhz. poor stability is one thing. Frying expansion cards is another, or frying your board because the cards fry. It's not that 440bx cannot handle 133 mhz, its that majority of the boards don't have dividers, like you see on good Pentium 4 boards.

You need to take into account also the more sticks of ram you slot the more stress that is putting on the VRM.
Like as if most 440bx actually have what in modern times is considered a VRM.
Add a power hungry GPU a fe expansion cards and decide to run your fans off the motherboard headers, it's a recipe for disaster.

These are very good points . I will add the following.

The BX6 2.0 does have the required divider (4) for running PCI at 33MHz when FSB is 133MHz, do no issue here if properly configured .

As for AGP, the usual dividers for running at either at FSB speed or 2/3 FSB speed are available, so even when everything is set properly AGP base clock will be 89MHz instead of 66 MHz when running FSB at 133 MHz . This 89MHz AGP clock is a limitation common to all 440BX boards when running 133MHz FSB . There is a list of AGP cards (mostly Nvidia) unofficially able to handle 89MHz on vogons.
EDIT: See here 440BX 133Mhz FSB 89Mhz AGP Video Card Compatibility?

The stress on VRMs is one thing to consider, though, AFAIK, the Abit BX6 2.0 was a high end board overclocker-friendly board and likely has somewhat overspecced VRM design. Somebody with specific knowledge on this board may want to chime in .

The stability issue with using more than 2 or 3 RAM slots at 133MHis likely due, at least in part), to the added stress on the 440BX memory controller, IMHO .

I agree that the 440BX chipset is capable of unofficial 133MHz operation, within limits, and that how well that works in practice is dependant on motherboard implementation . AFAIK, the Asus P3B-F and Abit BX6 2.0 are two of the better ones in that respect .

Finally, I will add that Abit boards of that era are unfortunately known for often having cheap capacitors that are prone to failure and may impact stability . Recapping may be necessary .

Reply 16 of 24, by dionb

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nwsw wrote on 2020-08-02, 04:36:
I did a ton of testing using all possible combinations of the following SDRAM that I own in 66/100/133mhz (yes, that many memtes […]
Show full quote
dionb wrote on 2020-08-02, 00:27:
darry wrote on 2020-08-02, 00:12:
[...] […]
Show full quote

[...]

The 440BX chipset only supports a max DIMM size of 256MB . Only 256MB will be usable of a 512MB DIMM . CPU-Z will likely report the total capacity of installed DIMMs regardless of what is actually usable .

PC 133 512MB SDRAM + PC 256 MB SDRAM x2 should yield up to to 768 MB or as little as 512MB (depending on whether 256MB DIMMs are recognized as 128MB or 256MB each, depending on density, 512MB DIMMs will be seen at 256MB each).
PC 133 512MB SDRAM x2 + PC 256 MB SDRAM x2 should yield up to 1024MB or as little as 768MB (depending on whether 256MB DIMMs are recognized as 128MB or 256MB each, depending on density, 512MB DIMMs will be seen at 256MB each).

Exactly.

What concerns me: why is BIOS reporting 756MB not 768MB? Given it's a BX there's no integrated VGA. The 32MB difference is the exact size of the 32Mx8 chips on the 512MB DIMM. Almost sounds like one is bad...

I did a ton of testing using all possible combinations of the following SDRAM that I own in 66/100/133mhz (yes, that many memtests and windows boots):
4x PC 100 256MB SDRAM
4x PC 133 256MB SDRAM
2x PC 133 512MB SDRAM

My main findings:

1. CPU-Z somehow recognizes the full 512MB where the BIOS/memtest86/Windows only recognize 256MB. That answers the main question of the thread.
2. Windows XP/Vista/7 will give an unsupported ACPI error when booting at 133mhz with more than 512MB of physical RAM. ACPI is recognized and has no issues with 512MB RAM or less, additionally with up to 1024MB at 66/10omhz. Installations also blue screen at 133mhz at some point with more than 512MB RAM.
3. All RAM (including 512MB) passes memtest86 at 66/100mhz. My 4x 256MB PC 133 and 2x 512MB 133 will give many test 3 and test 4 errors at 133mhz in all combinations above 512MB ram.
4. I think my PC is stuck in the Gamma Quadrant with a severe lack of dilithium.

At this point I am going to benchmark 933mhz (133mhz clock) with 512 MB PC 133 versus 700 mhz (100mhz clock) with 1024MB PC 100. To the 3dmarks!

1) it has nothing to do with "recognition", CPU-Z reads SPD EPROM on the DIMM, the memory controller addresses what it can address (max 128Mb per chip, as the link already posted made clear)

3) why on earth mess around with unsupported 512MB DIMMs on a BX board if you have regular 256MB DIMMs? Are they single-sided (8 chips of 32Mx8) or dual-sided (16 chips of 16Mx8)? If single-sided they're no better than 512MB, as once again, max 128Mb per chip on BX. If dual-sided, they are an ideal match for the board and at least remove any confusion regarding half-utilized modules.

2+4: how about some consistent testing? Abit boards have LOTS of timing settings for RAM. Try relaxing them - particularly CAS latency; your memory controller may well do CL2 at 100MHz, but 133MHz *and* a fully loaded bus might require CL3. Also consider subtly increasing VDIMM, as you're probably hitting simple electrical barriers here.

I'm still intrigued about 756MB vs 768MB? It's almost as if the last chip or two on the bus simply doesn't have the power to function anymore.

Reply 17 of 24, by matze79

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440BX only supports double side 256Mbyte SD-RAM, so the 512Mbyte Sticks are only used half.

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Reply 19 of 24, by PARKE

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darry wrote on 2020-08-02, 05:17:

133MHz is technically overclocked for a 440BX board, so stability issues or constraints may appear when running at that speed . My Asus P3B-F, for example, will not recognize more than 3 of its 4 DIMM sockets when running at that speed, other boards will behave differently .

A similar symptom occurs on an ASUS P2B-D rev.1.06 here. It runs fine on fsb 100 with 4x256MB pc100 sticks but with 2xPIII 1Ghz fsb 133 and 4x256MB pc 133 sticks in either reports only 512MB or 768MB depending on which stick sits in which slot.