Your MFM/RLL hard disk controller is missing a backplate.

You need two cables to hook up a disk.

Is this isa card actually i not have it saw on listing

google WDC WDXT-GEN2PLUS
https://www.minuszerodegrees.net/manuals/West … ion%20Guide.pdf

Seller informs this is from compaq portable pc

Can i use this for fdd and old hdds?

Manual for card is here, as mentioned in previous post, https://www.minuszerodegrees.net/manuals/West … ion%20Guide.pdf .

Only HDD.
not for FDD.

If you dont have MFM HDDs its totally useless. (As far as i know there are no modern recreations to simulate MFM HDDs, so you have no other option to buy a real MFM HDD)
MFM is getting really rare and expensive... Better get a cheap IDE controller or multi IO card.

DerBaum wrote on 2023-12-25, 17:08:

If you dont have MFM HDDs its totally useless. (As far as i know there are no modern recreations to simulate MFM HDDs, so you have no other option to buy a real MFM HDD)
MFM is getting really rare and expensive... Better get a cheap IDE controller or multi IO card.

There are at least two emulators: https://www.drem.info/ and https://www.pdp8online.com/mfm/mfm.shtml

mkarcher wrote on 2023-12-25, 18:24:

DerBaum wrote on 2023-12-25, 17:08:

If you dont have MFM HDDs its totally useless. (As far as i know there are no modern recreations to simulate MFM HDDs, so you have no other option to buy a real MFM HDD)
MFM is getting really rare and expensive... Better get a cheap IDE controller or multi IO card.

There are at least two emulators: https://www.drem.info/ and https://www.pdp8online.com/mfm/mfm.shtml

I should have said "affordable" options...

Nice that they exist.
But 300 / 150 Money is a little bit much...
Who in his right mind would buy that if you can get a IDE controller and drive (or CF / SD card) for a fraction of the cost...

Except you have committed yourself to save a MFM system for any cost...

Make sure you plug it in the right way round. I fried one of these by connecting it the wrong way. (Fortunately the computer was unharmed.)

DerBaum wrote on 2023-12-25, 19:28:

mkarcher wrote on 2023-12-25, 18:24:

DerBaum wrote on 2023-12-25, 17:08:

If you dont have MFM HDDs its totally useless. (As far as i know there are no modern recreations to simulate MFM HDDs, so you have no other option to buy a real MFM HDD)
MFM is getting really rare and expensive... Better get a cheap IDE controller or multi IO card.

There are at least two emulators: https://www.drem.info/ and https://www.pdp8online.com/mfm/mfm.shtml

I should have said "affordable" options...

Emulating MFM disk is not really all that much different from emulating floppy the way Gotek and its siblings do. Its totally doable with $5 pico reading HDD image from USB pendrive.

rasz_pl wrote on 2023-12-27, 21:32:

DerBaum wrote on 2023-12-25, 19:28:

mkarcher wrote on 2023-12-25, 18:24:

There are at least two emulators: https://www.drem.info/ and https://www.pdp8online.com/mfm/mfm.shtml

I should have said "affordable" options...

Emulating MFM disk is not really all that much different from emulating floppy the way Gotek and its siblings do. Its totally doable with $5 pico reading HDD image from USB pendrive.

Can you link to a cheap solution?
I have a computer missing its MFM drive and it would be nice to use the original controller before i replace it.

Makes me wonder if the control signals can be shared with a real hard drive and the emulator, while the emulator delivers the data, the hard drive delivers the original sound.

Doable as in "go ahead and do it" 😜 Im hoping to inspire someone like I nudged Polpo to pico instead of full expensive and complicated rpi Re: PiGUS: Gravis Ultrasound emulator on an ISA card with Raspberry Pi :]

weedeewee wrote on 2023-12-27, 22:06:

Makes me wonder if the control signals can be shared with a real hard drive and the emulator, while the emulator delivers the data, the hard drive delivers the original sound.

I think either Adrian (Adrian's Digital Basement) or Epictronics or Tony359 mentioned planning something like that recently in one of PC restoration Videos 😀 run old drive with arduino while emulator takes care of data delivery.

rasz_pl wrote on 2023-12-27, 22:33:

Doable as in "go ahead and do it" 😜

I dont even have any understanding of how mfm works. thats way over my head to even think about doing something like this by myself...

DerBaum wrote on 2023-12-28, 00:42:

rasz_pl wrote on 2023-12-27, 22:33:

Doable as in "go ahead and do it" 😜

I dont even have any understanding of how mfm works. thats way over my head to even think about doing something like this by myself...

There is open source firmwar available for a floppy emulator https://github.com/keirf/FlashFloppy
MFM HDD is just a bigger floppy. Differences are:

• data transferred to/from controller over differential pairs (RS-422) vs floppy single ended open-collector. This just means you need $0.2 8 pin chip (SN75176B or similar).
• up to 8 platters, so 16 heads vs 2.
• rotates 10x faster, 3600 vs 360 rpm.
• 10x faster bitrate thanks to above, 5000 vs 500 Kbit.
• more tracks thanks to solid non-floppy platters and sturdier case, >150 vs 80 per side.

Everything else is the same. 90% of work is already implemented by floppy emulators. Whats left is programming Pico PIO/DMA engine interface to provide 10x faster data transmission compared to STM32 floppy emus.

What really surprised me was learning how primitive early HDDs were. Even IDE ones like 1989 $500 Seagate ST157a
https://stason.org/TULARC/pc/hard-drives-hdd/ … -HH-IDE-AT.html
, manufactured all the way to ~1992 when it still sold for around $180, is very much a floppy rotating 10x faster enclosed in a metal box. Denser tracks at 650 vs 135 tpi, but almost two times lower Bit density compared to ordinary floppy drive 10000 vs 17434 bpi.