SD cards are completely different to DRAM, so no, you couldn't do that sensibly. The flash would wear out much too soon.

As for EDO-DRAM vs SDRAM, remember that EDO and SDRAM are RAM types, not physical formats. In particular, EDO wasn't limited to 72p SIMMs, there are also 168p EDO DIMMs, including (rare) 3.3V examples. So you definitely can physically put a 3.3V 168p EDO DIMM on a P4 motherboard with i845B chipset. The question is if the chipset can talk EDO.

The answer there is tricky as I can't find a datasheet for the i845B chipset, but the product brief only mentions PC133 and DDR200/266: https://theretroweb.com/chip/documentation/27 … 1d571401906.pdf

As far as I can see, Via KT133(A/E) and KT266 Athlon chipsets don't support it either.

What definitely does is Via ApolloPro133A, which supports up to P3-1100E in-spec, but if it does, the virtually identifcal 694T (that I can't find a datasheet for) almost certainly does too, which means Tualatins up to P3-1400S could be run with EDO. Moreover these Via chipsets allow asynchronous clocking of the memory, which is useful as the fastest EDO I've seen is 50ns, which won't handle 133MHz...

Now, as for whether you could rig up some kind of abomination to interface two SIMMs to a 168p DIMM interface... I've never seen one, but apart from data skew considerations it should be possible. It was relatively common with 30p (FP) SIMMs to 72p SIMMs, and it was even done with abominations interfacing two 168p DIMM slots to an MTH which would then go into a RIMM slot.

Timing issues may prevent a simm to dimm tree.

BX Boards benefit from EDO if you just want a lot of ram

There were EDOs on DIMMs, I have a 32MB one like that but I have yet to find a board where it actually works.

Tiido wrote on 2025-01-07, 22:42:

There were EDOs on DIMMs, I have a 32MB one like that but I have yet to find a board where it actually works.

The attachment EDODIMM.jpg is no longer available

I have a 64MB unbuffered 3.3V EDO DIMM that works fine on my BX and MVP3 boards (and probably a lot more - just never felt like trying). Are you sure the DIMM actually works?

I have an IBM Pentium MMX computer that can use either EDO or SDRAM DIMMs. A novelty, really, because I'd rather use SDRAM of the two.

dionb wrote on 2025-01-07, 23:08:

I have a 64MB unbuffered 3.3V EDO DIMM that works fine on my BX and MVP3 boards (and probably a lot more - just never felt like trying). Are you sure the DIMM actually works?

It didn't work on a BX board I had, but it also didn't like almost any SDRAM I tried in it either. I actually do have a MVP3 board but I never tried this on it, perhaps it'll work there but that board is much better off with proper SDRAMs anyway 🤣. But I do not know if it works or not, I don't even remember where it came from but I am certainly keeping it as a curiosity 🤣.

dionb wrote on 2025-01-07, 21:39:

SD cards are completely different to DRAM, so no, you couldn't do that sensibly. The flash would wear out much too soon. […]
Show full quote

SD cards are completely different to DRAM, so no, you couldn't do that sensibly. The flash would wear out much too soon.

As for EDO-DRAM vs SDRAM, remember that EDO and SDRAM are RAM types, not physical formats. In particular, EDO wasn't limited to 72p SIMMs, there are also 168p EDO DIMMs, including (rare) 3.3V examples. So you definitely can physically put a 3.3V 168p EDO DIMM on a P4 motherboard with i845B chipset. The question is if the chipset can talk EDO.

The answer there is tricky as I can't find a datasheet for the i845B chipset, but the product brief only mentions PC133 and DDR200/266: https://theretroweb.com/chip/documentation/27 … 1d571401906.pdf

As far as I can see, Via KT133(A/E) and KT266 Athlon chipsets don't support it either.

What definitely does is Via ApolloPro133A, which supports up to P3-1100E in-spec, but if it does, the virtually identifcal 694T (that I can't find a datasheet for) almost certainly does too, which means Tualatins up to P3-1400S could be run with EDO. Moreover these Via chipsets allow asynchronous clocking of the memory, which is useful as the fastest EDO I've seen is 50ns, which won't handle 133MHz...

Now, as for whether you could rig up some kind of abomination to interface two SIMMs to a 168p DIMM interface... I've never seen one, but apart from data skew considerations it should be possible. It was relatively common with 30p (FP) SIMMs to 72p SIMMs, and it was even done with abominations interfacing two 168p DIMM slots to an MTH which would then go into a RIMM slot.

Sd cards? No sdram haha

Otherwise, good response 😀

So the via P3 may be the best for a edo setup

Tiido wrote on 2025-01-07, 22:42:

There were EDOs on DIMMs, I have a 32MB one like that but I have yet to find a board where it actually works.

The attachment EDODIMM.jpg is no longer available

Yep, that’s basically what I’m talking about.

I was figuring since those exist, and adaptet with two simms could exist also (rather, could be made, not that there is a point other than boredom though)

Sphere478 wrote on 2025-01-08, 01:23:

Tiido wrote on 2025-01-07, 22:42:

There were EDOs on DIMMs, I have a 32MB one like that but I have yet to find a board where it actually works.

The attachment EDODIMM.jpg is no longer available

Yep, that’s basically what I’m talking about.

I was figuring since those exist, and adaptet with two simms could exist also (rather, could be made, not that there is a point other than boredom though)

128mb and 256mb EDO dimms have become “uncommon” (more so than 64mb simms) . I do not know what type of memory layouts are allowed but a stack of 2x or 4x 64mb simms would allow some machines to be “maxed out” that otherwise are difficult to do so.

Thing is I have no idea what chip configurations would be allowed, the 3.3 volt / 5 volt only limitations of some machines may also be a bummer as is buffering requirements.

I do not know if inventories of large/fast EDO “chips” exist anymore but that may be the path of least resistance.

That said I have owned several “EDO ONLY” machines that only accepted dimms for some reason and once you get up to 64mb+ things get rare/pricey these days.

That said we are getting pretty niche for the machines that used dimms but had issues with sdram. There are also potential “keying” issues as FPM / EDO dimms came with some oddities depending on the system

Oddly the PCCHIPS m571 was easier to max with 1x EDO dimms and 4x simms as large amounts of sdram was unstable

So fastest I've run personally are K6-2s at 450 on 430HX and 430TX boards. Some Slot 1 and 370 boards with 430LX and EX are around with SIMM sockets, meaning you can probably go up to 766 Celeron on those, or Tualeron around 1ghz with a 1.4, a powerleap adapter or similar and 75mhz bus. PC Chips were fond of clinging to SIMMs more so than other brands.

Unbuffered EDO DIMM's work for example on 440FX (I have IBM PC365 dual socket 8 ), it only accepts those and nothing else.

I could try them on LX or BX board, have several to try.

Unbuffered EDO DIMM was common on PPro platforms while many Compaq serveres used buffered EDO Dimms and even buffered FPM.
Some systems like the Vectra XU use 5V buffered EDO.
Some IBMs from the 300/700 series had memory slots for PS/2 as well as for a single 5V buffered EDO DIMM.
Got some Kingston 3,3V EDO Dimms originally made for some IBM systems (KTM-label) running flawlessly but slightly slower than SDRAM in an LX-board.

Yes, I have Compaq Professional Workstation 5100 which has some custom Compaq chipset (made by RCC), dual Pentium II and uses buffered EDO DIMMs.
When I got the IBM PC365 I was sure I had enough RAM but obvisously the sticks were keyed differently. Doh. Bought 4x 128 MB sticks for PC365 from ebay for 11eur per stick.

eisapc wrote on 2025-01-08, 16:15:

Unbuffered EDO DIMM was common on PPro platforms while many Compaq serveres used buffered EDO Dimms and even buffered FPM. Some […]
Show full quote

Unbuffered EDO DIMM was common on PPro platforms while many Compaq serveres used buffered EDO Dimms and even buffered FPM.
Some systems like the Vectra XU use 5V buffered EDO.
Some IBMs from the 300/700 series had memory slots for PS/2 as well as for a single 5V buffered EDO DIMM.
Got some Kingston 3,3V EDO Dimms originally made for some IBM systems (KTM-label) running flawlessly but slightly slower than SDRAM in an LX-board.

i think the fastest platform using edo ram is 450nx mainboard with quad p3xeon900-2m, but it uses 168pin edo dimms.
fastest platform with simm is probably mvp3 mainboard with 2mb cache and k6-3+.

It occurs to me that some orangepc cards could use such a simm contraption.

OrangePC 530 pinout, bios update, vram upgrade

Sphere478 wrote on 2025-01-09, 02:36:

It occurs to me that some orangepc cards could use such a simm contraption.

OrangePC 530 pinout, bios update, vram upgrade

Not an EDO one - that OrangePC 530 requires FP DIMMs, and even though explicit specs are hard to find, the images I see look like the DIMMs are buffered, so it would take a bit more than two unbuffered SIMMs to get that to work.

I also wouldn't bother - buffered FP (and EDO) DIMMs are a lot easier to find than unbuffered ones - tons on a well-known auction site for less than USD 10 and a couple on this side of the pond for EUR 15 or so. You're not going to homebrew for less than that.

dionb wrote on 2025-01-09, 07:23:

Sphere478 wrote on 2025-01-09, 02:36:

It occurs to me that some orangepc cards could use such a simm contraption.

OrangePC 530 pinout, bios update, vram upgrade

Not an EDO one - that OrangePC 530 requires FP DIMMs, and even though explicit specs are hard to find, the images I see look like the DIMMs are buffered, so it would take a bit more than two unbuffered SIMMs to get that to work.

I also wouldn't bother - buffered FP (and EDO) DIMMs are a lot easier to find than unbuffered ones - tons on a well-known auction site for less than USD 10 and a couple on this side of the pond for EUR 15 or so. You're not going to homebrew for less than that.

Can you convert buffered back to unbuffered?

rmay635703 wrote on 2025-01-10, 04:04:

[...]

Can you convert buffered back to unbuffered?

Never say never, but would need so much re-wiring you're better off harvesting the chips and putting them on a new unbuffered PCB.