I got my SD card extender from eBay and can't find the make or model online. It did come from China though 🤣. The biggest SD card I was able to get working was 2GB which is the limit of the FAT16 file system. I was also able to get 256MB and 512MB cards working.

I now use one of these:

It only works with a full sized SD card, not with a miniSD to SD adapter.
It is important to use a UHS Class 1 (Class 10) SD card.
The old non UHS SD cards are slower with small files even though the benchamarks show they are as fast as an HDD, they just don't respond as fast as the UHS Class 1 cards.

I got a Transcend Ultimate 32GB and it feels much faster than my old 20GB WD HDD with this adapter.

Unfortunately Windows 98 SE with my Intel 430TX motherboard I cannot enable DMA for the else my system freezes.
I'll post some benchmarks soon.

I cannot enable DMA for the else my system freezes.
I'll post some benchmarks soon.

This also happens to some CF-Card Adapters which are simply misswired.
I also had this and needed to mod the Adapter with a bit of copper wire.

I experimented too with SDCard to IDE Adapters and can't really recommend them.
I had problems with it.
Situation: A Game locks up the PC, you turn the Power off and on -> SDCard corrupt.
I also experimented with mSATA to IDE Adapters.

Which performe well, but also often enable UDMA Mode 5/Mode 6 by Default. Some SDCard Adapter also do this.
Maybe you have same Problem and need to force the Adapter to DMA Mode 2.
Because of your Mainboard not supporting newer Modes.
In that Case Enabling DMA will fail within 98.
I also got this Problems.
A BIOS fix with bpatcher did the job, my Motherboard was hanging on boot because of dma issues. Did only boot with PIO only. (But not always..)
Under MS-Dos you could use the older version of the udma .sys driver from FreeDOS Project to Force DMA Mode 2.
And see if it works (Win98 is not combatible with this driver).

Eventually the Device will fallback to dma2 when using a 40pin cable.

You also can use the http://alter.org.ua/soft/win/uni_ata Universal ATA Driver.
There is a Windows 9x Build out in the Wild.
Maybe DMA works with this.

Win 9x/ME support (now we have separate build with some limitation, thanks to Xeno)

i simply changed to a Promise PCI Controller later, the 430TX Chipset limits Performance of my mSATA2PATA SSD

The UDMA problem is not only with the SD card adapter but with the HDD (UDMA 4) too.
My 430TX motherboard only supports up to Mode 2, but I have no way to change it in the Bios, it's either DISABLE or AUTO.

A BIOS fix with bpatcher did the job.

What job? Force UDMA Mode 2?
Can you please guide me how?

This is mainly a DOS computer, but I installed WIN98SE to transfer large amount of data through the Network card or USB like copying games.

HDD's do always support fallback (except some bleeding Edge 750Gb PATA HDDs... ), so the problem is somewhere else.

did you connect CD-Rom and HDD on same cable ?

I tried to disconnect the CD-ROM but it also failed.
The DMA switch simply doesn't stays ticked.

I've seen this on some motherboards. They just can't do it. Not sticking is not the worst behaviour, many boards will just stop booting with a black screen. Sometimes only a re-installation solves this. So when I test DMA enabling, I take an image of the drive first.

Well alright then, it's a DOS computer anyway.
The UHS SD card performs better than the HDD anyway.

As said, try DOS UDMA Driver and see if it works 😀 then you can be sure.

James-F wrote:

I now use one of these: http://img.dxcdn.com/productimages/sku_10889_2.jpg […]
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I now use one of these:

I use these too, but have them with a female IDE connector instead. They work well for me. Not as fast as the Transcend DOMs (Disk on Module), but SD is far easier to transfer things to and from a modern system. Some older BIOS'es have an issue with SD cards, where disk autodetect is failing, and it only works with manually entered parameters. But since I found unofficially patched BIOS'es all is well.

matze79 wrote:

As said, try DOS UDMA Driver and see if it works 😀 then you can be sure.

Nope, doesn't work.

Says:

1UltraDMA controller found at PCI address F000h.
2    Intel 82371AB/EB/MB, bus 00h, device 07h, function 1.
3Doing hardware-only disk scan.
4Primary-master disk FAILED read test! Hard error at I-O end.
5No UltraDMA disk to use; driver NOT loaded!

It actually finds the motherboard UDMA controller but fails reading the disk......?

Anyway, I don't really care, it is a DOS machine.