Syntho wrote on 2024-07-21, 08:55:

I've got a couple SIMMS in my Intel 133 machine. Only 16mb in total. The board also has a single DIMM slot. If you look at the manual on page 44 of the pdf (2-30 in printed manual) you'll see that it gives allowed combinations of mix-matching RAM, and also says it allows for 128mb total. What doesn't make sense is that the combos shown equal a total of only 96mb, unless I'm reading this wrong. Is the max size of a DIMM stick 32mb? Confusing.

I just want to get at least 64mb of RAM in there. What kind of RAM would you recommend for this board?

Will be helpful if you can post a link to your motherboard on the Retroweb or provide the model number.

jesolo wrote on 2024-07-21, 10:14:

Syntho wrote on 2024-07-21, 08:55:

I've got a couple SIMMS in my Intel 133 machine. Only 16mb in total. The board also has a single DIMM slot. If you look at the manual on page 44 of the pdf (2-30 in printed manual) you'll see that it gives allowed combinations of mix-matching RAM, and also says it allows for 128mb total. What doesn't make sense is that the combos shown equal a total of only 96mb, unless I'm reading this wrong. Is the max size of a DIMM stick 32mb? Confusing.

I just want to get at least 64mb of RAM in there. What kind of RAM would you recommend for this board?

Will be helpful if you can post a link to your motherboard on the Retroweb or provide the model number.

I hit Command+V on my Mac to paste the link but it didn't paste, and I failed to check before I submitted the post 😀 https://theretroweb.com/motherboard/manual/ap … c3515068242.pdf

I am familiar with the AOpen AP5VM... IIRC, this was the dawn of SDRAM.

You can only use all the SIMM and DIMM slots if the same RAM type was used for both. Which meant skipping SDRAM and finding the rare FPM or EDO DIMM to get it to work.

The reality was folks would just stick to one slot type or the other but rarely both.

I'm wondering if I should go with some SIMMs, or a single DIMM, and which size I'm limited to on a DIMM. The page I pointed out mentions a 32mb DIMM but elsewhere it seems like it could be even more. I'm not sure what to do here.

VX Chipset, so don't use more than 64MB ram if you intend to use win9x/me.

The confusing part is that it says in the manual that it accepts up to 128mb, and gives a chart as mentioned in my OP that doesn't add up anywhere to 128mb. And on some other pages (42-48 or so) it says it accepts a 128mb DIMM and a 32mb SIMM. That's kind of contradicted by the chart on page 44 of the pdf (2-30).

On the other hand, maybe they were talking about single-sided RAM, and if I get double sided I can just double the amount there?

And if there's a problem with more than 64mb, no problem. If I can get a single DIMM in 64mb I'd just go with that, unless two 32mb SIMMs would be better.

It's likely that you can combine both dimm & simm slots IF! you use the same memory type for both ie EDO

You have to use TWO ! simms at the same time at minimum. I don't think there is any intel chipset for a pentium cpu that allows only one 72p simm to be used due to the 64bit memory bus since a 72p simm is 32 bit wide.
A dimm is 64 bit, so if you choose to use only the dimm either sdr or edo can be used.

and as already has been stated, to get the best performance, limiting the memory to only 64M is best.

Your sweet spot on the AOpen AP5VM is a single 64MB PC66 DDR DIMM to stay within the cacheable memory limitation of the Intel VX chipset. A pair of 32MB EDO SIMMs will provide about the same performance.

Should you wish to exceed the 64MB limit, please know when the manual was written PC66 DDR DIMMs greater than 32MB just did not exist on the consumer market if at all.

Sorry to be like this, but it's SDRAM, not DDR 😀

oh2ftu wrote on 2024-07-21, 16:07:

Sorry to be like this, but it's SDRAM, not DDR 😀

Oh no, you're absolutely right! Mea culpa.

Syntho wrote on 2024-07-21, 15:03:

The confusing part is that it says in the manual that it accepts up to 128mb, and gives a chart as mentioned in my OP that doesn't add up anywhere to 128mb. And on some other pages (42-48 or so) it says it accepts a 128mb DIMM and a 32mb SIMM. That's kind of contradicted by the chart on page 44 of the pdf (2-30).

The chart doesn't contradict the earlier statements, it only illustrates realistic configurations at time of writing.

Remember, that manual was intended for people building a system in 1996, not for people messing around with it almost 30 years later. Back then, Windows 95 was relatively new and 24MB was more than enough to run it smoothly, more than 32MB was prohibitively expensive and more relevant: the i430VX was released alongside the i430HX which was specifically aimed at workstation workloads. i430VX was desktop-only. If you wanted more RAM in 1996, AOpen would have referred you to their AP53 i430HX board. So there was no reason to elaborate on higher memory numbers.

That said, this is a generic i430VX board, so:

SIMMs (FP or EDO): simple, max 32MB per SIMM, to be installed in pairs. Max total 4x 32MB = 128MB. All SIMMs need to be same standard (FP or EDO) but apart from that any combination of pairs will work.
DIMM: complicated. i430VX was the first SDRAM chipset. Compatibility was limited. In general, 8-chip 16MB and 16-chip 32MB DIMMs (i.e. 16Mb chips ) will work. 64Mb chips sometimes work, so 2-chip 16MB, 4-chip 32MB, 8-chip 64MB and 16-chip 128MB DIMMs could work. But don't bank on it...

On the other hand, maybe they were talking about single-sided RAM, and if I get double sided I can just double the amount there?

No, it's pretty explicit about that. In fact this is probably the most extensive description I've seen (up to and including checking presence of 4 specific pins for discovering info about DIMMs).

And if there's a problem with more than 64mb, no problem. If I can get a single DIMM in 64mb I'd just go with that, unless two 32mb SIMMs would be better.

Ironically despite huge numbers of pages about RAM, the manual completely fails to mention the cacheable limit of 64MB on this chipset so also on this board. You can install up to 128MB on it, but the top 64MB will not be cached by the L2 cache. TLDR, it nerfs performance in DOS and Win9x. Only situation in which you would want to use >64MB on a board like this is if you actually use >64MB and are thrashing to disk regularly, as uncached RAM access is still vastly faster than HDD access. However it's unlikely software that needs more will run acceptably on a VX system anyway, so just stick with 32-64MB.

SDRAM is definitely faster than EDO on i430VX, but as stated, chances of a random 64MB DIMM working are slim. So be sure to have 2x 32MB SIMMs as plan B.

Nobody mentioned that they probably have to be 5V EDO DIMM to play nice with EDO SIMM, as opposed to 3.3V, never come across the 3.3V myself, but some boards have jumpers/switches for 5V or 3.3.

Most common EDO DIMM that collected up from random RAM lots here is the 16MB it seems, got one 32 and one 8 also. When it gets down to finding the last few CPU holes for my sub 200Mhz socket 7 class, I'd probably be happy enough mixing the EDO DIMMs up with SIMMs on a VX board or two, particularly since 4MB EDO has "bred" on me and I can have 4x4 +16 for 32Mb which for 96ish was a decent enough amount of RAM. The only time it's way slower is if it is just regular write back cache and not pipeline burst, PLB plus EDO is a few percent slower than SDRAM w/256k and barely noticeable percentage with 512k, with writeback it's 15% or so.

BitWrangler wrote on 2024-07-21, 22:53:

Nobody mentioned that they probably have to be 5V EDO DIMM to play nice with EDO SIMM, as opposed to 3.3V, never come across the 3.3V myself, but some boards have jumpers/switches for 5V or 3.3.

It's explicitly discussed on pages 2-31 and 2-32 of the manual. DIMMs must be 3.3V units and keyed as such, and if you want to pair them with SIMMs they must also be 5V tolerant.

Tbh the bigger challenge with EDO DIMMs is finding unbuffered ones, as most systems using 168p EDO stuff use buffered DIMMs, which are incompatible and won't physically fit.

I went ahead and got some SIMMS instead. 2x 32mb sticks. Thanks for the all the info. I'll keep it in mind for when I run into any other issues like this.