While PC-133 should be backwards compatible (i.e. run at lower speed), look at your mainboard's documentation, it should say what's supported. At least least size-wise, but usually the manufacturer's site also has a(n incomplete) list of specific ram sticks that they tested, you may be able to derive some additional info from that. And then there's theretroweb.com.

Putting aside the compatibility question for a mo - what OS would you be using anyways? Because while maxing stuff out can be fun, even if the board supports it, the Win9x series starts developing all kinds of issues above 512 megs, so if that's what you're using I'd recommend picking up a 256MB stick and calling it a day.

Zukovsky wrote on 2024-03-09, 21:05:

I went to put in another stick of 512mb pc-133 ram and even though the system bios recognize that 512mb is in bank 1, the system memory is still 64mb.

What system reports 64MB? If I remember correctly, the HIMEM driver shipped with MS-DOS 6.22 is limited to 64MB. Windows 95 should be able to see all your RAM, though.

Some older chipsets, I'd say older than i815 approximately or VIA 694, do not recognize such high capacity modules.

I'd suggest you using 256mb ram modules. If you need 512mb for some reason it's better to combine 128 or 256 sticks than trying a 512mb one.

P3 Gateway most likely be an Intel OEM 440BX board (E205351?), max ram per slot on any 440BX is 256Mb AFAIK

I seem to remember that some of the later 256mb sdram modules also did not work in BX boards due to their use of higher density chips unsupported by the chipset.

Yes, 440BX can be picky on ram. It is an Intel WS440BX (Tabor or Jabil variant) according to Gateway. Some have onboard audio and ethernet, some do not....

Horun wrote on 2024-03-10, 03:39:

Yes, 440BX can be picky on ram. It is an Intel WS440BX (Tabor or Jabil variant) according to Gateway. Some have onboard audio and ethernet, some do not....

I worked at a computer store during this time period and we had to mark SDRAM as "Intel" or "Non Intel" because of Intel chipsets not liking the higher density stuff.

Agree with everyone else
I'm betting the ram is double sided, where as the motherboard only accepts Single sided ram.
It is possible to find single sided 512MB sticks, but its far easier just to get a couple of 256 or 128 sticks.

The fact it's PC-133 doesn't matter

I’ve got a gateway system with a Jabil Tabor motherboard. https://theretroweb.com/motherboards/s/intel- … -mount-prospect

The manual says that it accepts 128MB dimms 384 max. I tried it with 256MB dimms and it worked up t0 768 total with the newest BIOS. I tried larger 512MB sticks but it only recognized mine as 64MB.

Zukovsky wrote on 2024-03-09, 21:05:

I went to put in another stick of 512mb pc-133 ram and even though the system bios recognize that 512mb is in bank 1

how? can you post a photo? is it a bios screen showing what is inserted into each DIMM slot? your description would suggest this info is just read from DIMM SPD (small config eprom on each memory module).

Exactly, that's just reading out the SPD.

As for the DIMM: 512MB SDR-SDRAM has 16 (or 18 if ECC) 256Mb chips with 32Mx8 structure. i440BX supports max 128Mb chips with 16Mx8 structure.

So that DIMM should work as 256MB DIMM.

chinny22 wrote on 2024-03-10, 23:04:

Agree with everyone else
I'm betting the ram is double sided, where as the motherboard only accepts Single sided ram.
It is possible to find single sided 512MB sticks, but its far easier just to get a couple of 256 or 128 sticks.

Unlikely that this is the main problem, and single-sided 512MB DIMM with 64Mx8 chips (was that even a thing with SDR-SDRAM?) would not help as it's even further beyond the 16Mx8 that would work.

Some BX boards only accepted double-sided DIMMs on first two slots and either double-sided in slot 3 with nothing in slot 4, or single-sided in 3 and 4.

However all BX boards will accept double-sided DIMMs in slot 1 and a good many will take double-sided DIMMs in all slots.

All this "Intel only" or "non-Intel only" is at best partly correct and in any case an oversimplification - sometimes it refers to chip density as here, with 128Mb chips supported by BX and 256Mb chips not supported. However later Intel chipsets (i8xx onwards) did support 256Mb chips, even if i810 and i815 were additionally limited to max 512MB total. This is more an age thing than a vendor thing, Via chipsets from 1998 also could address max 128Mb chips, it's just that they weren't being used in 2000 the way BX still was. Note that 128Mb was called 'high density' as opposed to earlier 64Mb chips, whereas it was called 'low density' as opposed to 256Mb chips. Terms like 'high' and 'low' density are completely relative and therefore meaningless without context.

"non-Intel only" or "Via-only" could also refer to non-JEDEC spec DIMMs with cheaper x4 chips instead of x8/x16 chips, so DIMMs 16 16Mx4 / 32Mx4 chips, 8 on each side, but logically just single sided. These wouldn't work on Intel chipsets, which stuck rigidly to JEDEC, as opposed to Via, which accepted anything that even remotely looked like a DIMM. Other chipset vendors behaviour with these non-standard DIMMs varies, as you'd expect outside of defined standards.

Thanks everyone! As a lot of people said it was probably the size of the ram. I just put in a 256mb stick for a total of 320mb and it is working perfectly.

Cheers

Here's a slightly related experience I had with a ECS P6EX-Me which is a 440EX based board.

Came with 2 double sided Dimms installed, each was marked 128MB but only 128MB RAM was recognized.

I figured one was bad but they both worked, but both getting recognized as 64MB.

I thought I new what to do so I pulled out a single sided 128MB DIMM. Still recognized as 64MB.

My supply of < 128MB DIMMS is getting low so on a lark, I tried one more double sided 128MB DIMM.

It detected as 128MB. Not sure what to make of that experience.

douglar wrote on 2024-04-04, 23:15:

Came with 2 double sided Dimms installed, each was marked 128MB but only 128MB RAM was recognized.

...

I tried one more double sided 128MB DIMM. It detected as 128MB. Not sure what to make of that experience.

Probably two things:

1. That board likely does not support more than 64MB per "rank". A rank is the technical term for the two "sides" of a memory module that can be accessed independently.
2. Electrical ranks are not equal to physical sides of the module. The double sided DIMMs you had in the system when you got it might have chips on both physical sides, but still build a single electrical rank. For example, if a chip only contributes 4 bits to the 64 bits required for each rank of a DIMM, a single-rank DIMM requires 16 of those chips. They may be mounted 8 chips on either side.

You can test my theory by checking the datasheet of the memory chips on the original 128MB modules. A 128MB SIMM built of 16 16Mx4 chips has a single rank. A 128MB SIMM built of 16 8Mx8 chips has two ranks.

mkarcher wrote on 2024-04-06, 16:49:

Probably two things: […]
Show full quote

Probably two things:

1. That board likely does not support more than 64MB per "rank". A rank is the technical term for the two "sides" of a memory module that can be accessed independently.
2. Electrical ranks are not equal to physical sides of the module. The double sided DIMMs you had in the system when you got it might have chips on both physical sides, but still build a single electrical rank. For example, if a chip only contributes 4 bits to the 64 bits required for each rank of a DIMM, a single-rank DIMM requires 16 of those chips. They may be mounted 8 chips on either side.

You can test my theory by checking the datasheet of the memory chips on the original 128MB modules. A 128MB SIMM built of 16 16Mx4 chips has a single rank. A 128MB SIMM built of 16 8Mx8 chips has two ranks.

Here are the DIMMs that I tried:

Showed 1/2 size: 4 chip DIMM - Hynix 256Mbit (4Mbit x 16 x 4 bank)
Showed 1/2 size: 16 chip DIMM - Micron 64 Mbit ( 2Mbit x 8 x 4 bank )
Showed 1/2 size: 4 chips DIMM - Generic 256Mbit (16Mbit x 16 )

Showed full size - 16 chip DIMM - Epida 64Mbit ( as 2Mbit × 8-bit × 4 bank )

Maybe I should retest the Micron DIMM.

douglar wrote on 2024-04-07, 14:42:

Here are the DIMMs that I tried: […]
Show full quote

Here are the DIMMs that I tried:

Showed 1/2 size: 4 chip DIMM - Hynix 256Mbit (4Mbit x 16 x 4 bank)
Showed 1/2 size: 16 chip DIMM - Micron 64 Mbit ( 2Mbit x 8 x 4 bank )
Showed 1/2 size: 4 chips DIMM - Generic 256Mbit (16Mbit x 16 )

Showed full size - 16 chip DIMM - Epida 64Mbit ( as 2Mbit × 8-bit × 4 bank )

Maybe I should retest the Micron DIMM.

The 4 chips DIMMs are definitely single sided, and fit the theory that ranks at 16M x 64 are unsupported. Re-testing the Micron DIMM makes a lot of sense, because the specs look like the Elpida DIMM that works perfectly. The board tops out at 8M x 64.

You don't write it as 16MBit x 16, but if you want to include the word "bit", you write it as "16M x 16bit", because it means that there are 16 "million" (actually 16777216) units of storage (not bits!), and each of these units consists of 16 bits. The generic 256 MBit chips likely are organized as 4 banks as well, so they would be 4M x 4 banks x 16 bit, just as the Hynix DIMM, it's just a less verbose and less specific way to write it.

I retested the one DIMM that should report as 128MB and it wasn't found at all on a retest. I cleaned the contacts and it came up as 128MB, so yeah, go ram! Maybe. I'll run memtest for a couple hours to make sure.

I also ran into someone with a bag of DIMMs they wanted to get rid of so I have more test material.

I tested three 8 chip DIMMs and they all tested out at the correct capacities, 64MB, 128MB, and surprisingly 256MB on both the EX & BX chipsets.
HYB39S64800CT-8 - 4 banks × 2 MBit × 8
HY57V28820HCT-H - 4 banks × 4 MBit × 8
Edit -- This was the wrong part--- HYB25D25600BT-6 - 4 banks × 8 MBit × 8

I also got two DIMMs with irregular notches. These look like proprietary registered EDO DIMMS of some sort maybe?

douglar wrote on 2024-04-13, 02:20:

I tested three 8 chip DIMMs and they all tested out at the correct capacities, 64MB, 128MB, and surprisingly 256MB on both the E […]
Show full quote

I tested three 8 chip DIMMs and they all tested out at the correct capacities, 64MB, 128MB, and surprisingly 256MB on both the EX & BX chipsets.
HYB39S64800CT-8 - 4 banks × 2 MBit × 8
HY57V28820HCT-H - 4 banks × 4 MBit × 8
HYB25D25600BT-6 - 4 banks × 8 MBit × 8

The 256MB one is really strange. Possibly you mixed up something, or the markings on the chip are completely fake. The HYB25D256800BT-6 is a DDR chip which requires 2.5V, so the DIMM should be keyed completely different from the (SDR) SDRAM DIMMs. 2.5V DDR memory only has a single notch, and doesn't fit SDR sockets at all...

The case of the HYB25F256800BT-6 chip is TSOPII-66 (according to the datasheet, and it matches your photo), which would provide enough pins for a x16 chip. So if that module indeed works in your system at 256MB, the chips have to be SDR SDRAM chips organized as 4 banks x 4M x 16bit. These chips do exist, like the MT48LC16M16A2, but those chips generally come in TSSOPII-54 packages according to official data sheets. Another theoretical possibility would be a module with a DDR/SDR translator chip that demultiplexes and level shifts the signals, but this makes absolutely no sense, because this kind of translation would add extra delay and extra complexity (anyone remeber the MTH fiasco?), and there was no need for translation, as SDR x16 chips are available even until today.

douglar wrote on 2024-04-13, 02:20:

These look like proprietary registered EDO DIMMS of some sort maybe?

Photo Apr 12 2024, 9 52 07 PM.jpg

These modules are 5V EDO DIMMs with address buffers. The left key is indicating "registered" for both modules, although the 162244 chips are not registers or latches, they are just buffers, and the right key is indicating 3.3V or 5V for the top EDO module and 5V only for the bottom EDO module. As far as I could find information, the chips on the top module are not specified to operate at 3.3V, so having a wide notch that allows insertion into 3.3V slots is technically wrong. OTOH, there were mainboards with jumperable RAM voltage (5V for PS/2 SIMM pairs, 3.3V for PC-type EDO DIMMs) having 3.3V-keyed slots. If you jumper those boards to 5V, they might provide 5V on a 3.3V slot and the top module may work perfectly in them.

During the research, I stumpled upon the claim that 5V buffered/"registered" EDO DIMMs were used by Apple in some Macintosh computers. You might call that proprietary, but it seems to be standardized by JEDEC.

mkarcher wrote on 2024-04-13, 07:50:

The 256MB one is really strange. Possibly you mixed up something, or the markings on the chip are completely fake. The HYB25D256800BT-6 is a DDR chip which requires 2.5V, so the DIMM should be keyed completely different from the (SDR) SDRAM DIMMs. 2.5V DDR memory only has a single notch, and doesn't fit SDR sockets at all...

Indeed, I mixed things up. Sorry about the confusion. Tried to do too much last night with a big bag of DIMMS while watching the kids and I had zoomed in too far on the photo to see the key.

Here is the correct photo of the 16 chip DIMM--

Samsung K6S280832a-TC1L - 4 bank PAGE BURST - 16Mx8bit -- https://www.datasheets360.com/part/detail/k4s … 63052022361220/

I'm surprised that it worked on the EX board and the BX board.

p.s. thanks for explaining about the voltage notch.