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Re: These are not the hard drives you are looking for Re: ABIOSDSK.386

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Thank you. My understanding is they are "true" IDE - they might have
some ESDI electronics IBM had lying around and "present" as the ESDI
controller, but, well, they're just like ATA, except this isn't an ATA
attachment, it's an MCA attachment. Perhaps it should be called MCAA.

It certainly does carry DMA - see the "ARB" pins. The IBM MFM and ESDI
controllers both used DMA (unlike inferior designs found in ISA
machines), and as attested by how my driver has to be careful not to run
into the usual "DMA in protected mode" type of problems.

Ultimately the McIDE controller could probably be adapted to this socket
- however, the McIDE does *not* present IBM ESDI/A or IBM MFM/A... and
there's no way to get a ROM in the DBA socket. I don't see anywhere that
responds to memory. I mean, I guess it could respond to 16-bit memory
acccesses and put ROM in the first 64KB of memory... not useful.

Louis Ohland <ohland@charter.net> wrote:
> Someone has to fill in for our missing pedantic Brit.
> 
> My understanding is the DBA-ESDI isn't ESDI. Chances are that IBM 
> appropriated "ESDI", trying to spiff-up the Integrated Drive used on the 
> 50z, 70, P70, and the early Model 90 [infamous -402].
> 
> My dark, inscrutable goal is to use the DBA-ESDI sockets for plug-in IDE 
> controllers. My kontuzion lies in the fact that the Integrated Drive has 
> it's own BIOS [or so I think], so the system doesn't need to support the 
> DBA-ESDI drive... ?
> 
> IBM DBA-ESDI Hard Drives
> https://ardent-tool.com/storage/DBA_ESDI.html
> 
> Direct Bus Attachment Pinout
> https://ardent-tool.com/storage/DBA_ESDI.html#Pinout
> 
> PS. Yes, the DBA-Socket is a stripped-down 16-bit slot. IIRC, it lacks 
> DMA. -BUT- it exists... The 50/70/90 were designed as a cable-less 
> systems. Some kompromises as to storage speed, but a PIO device on the 
> DBA-ESDI _should_ have comparable performance to the stock DBA-ESDI.
> 
> 
> Josh Rodd wrote:
> > Presenting ABIOSDSK.386: 32-bit disk access finally gets here for your
> > PS/2 with gigantic, clanking MFM drives and irreplaceable ESDI drives.
> > 
> > This has been about 35 years in coming, ever since as a sprightly 11
> > year old I was miffed that my fancy PS/2 P70 just wouldn't let me click
> > the "32-bit Disk Access", despite me barely understanding what was even
> > for. Of course, we now know that that means you can do things like open
> > a couple DOS windows on your 2MB machine and listen to the fixed disk
> > (or, more likely, a hard drive, since this wasn't happening on real IBM
> > computers with real IBM fixed disk adapters/A) thrash like crazy.
> > 
> > Nonetheless, here it is. It is based on IBM2ADSK.ADD from the OS/2 DDK
> > and WDCTRL from the Windows 3.1 DDK. So far, testing has been really
> > thorough: I tested it on 86Box with a Type 2 Model 80, ESDI adapter
> > card, PC DOS 3.30, 4MB and 2MB configurations, Windows 3.1. A test suite
> > program is included which tries to really exercise the disk and get
> > Windows' multitasking really crankin' with a couple DOS windows open.
> > 
> > Download it for yourself at:
> > https://github.com/sbooks-org/ABIOSDSK386
> > Direct link for 720kB floppy image, because how else would you get it on
> > your PS/2?
> > https://github.com/sbooks-org/ABIOSDSK386/releases/download/v0.90/ABIOSDSK.IMG
> > 
> > No warranty is implied, particularly given this is the kind of code
> > whose failure mode will mean you get to reformat your fixed disk and
> > reinstall everything.
> > 
> > I plan to do SCSI support next (it's easier than it sounds; it's just
> > another ABIOS interface). Can someone remind me what the state of
> > Windows 95 support for ABIOS disk adapters (MFM, ESDI, etc.) and the
> > PS/2 SCSI adapter is?
> > 

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Thread

ABIOSDSK.386: 32-bit disk access for your PS/2's MFM and ESDI drives "Josh Rodd" <joshua.at.rodd.dot.us@rodd.us> - 2026-08-08 02:48 +0000
  W95 and SCSI Louis Ohland <ohland@charter.net> - 2026-08-07 22:06 -0500
    Re: W95 and SCSI "Josh Rodd" <joshua.at.rodd.dot.us@rodd.us> - 2026-08-08 03:10 +0000
      Re: W95 and SCSI Louis Ohland <ohland@charter.net> - 2026-08-07 22:33 -0500
        Re: W95 and SCSI "Josh Rodd" <joshua.at.rodd.dot.us@rodd.us> - 2026-08-08 14:33 +0000
  FD had 32-bit BDA? Louis Ohland <ohland@charter.net> - 2026-08-07 22:08 -0500
    Re: FD had 32-bit BDA? "Josh Rodd" <joshua.at.rodd.dot.us@rodd.us> - 2026-08-08 03:11 +0000
    Re: FD had 32-bit BDA? "Josh Rodd" <joshua.at.rodd.dot.us@rodd.us> - 2026-08-08 03:12 +0000
  These are not the hard drives you are looking for Re: ABIOSDSK.386 Louis Ohland <ohland@charter.net> - 2026-08-08 07:03 -0500
    Re: These are not the hard drives you are looking for Re: ABIOSDSK.386 "Josh Rodd" <joshua.at.rodd.dot.us@rodd.us> - 2026-08-08 14:27 +0000
      -TC on A30 Re: ABIOSDSK.386 Louis Ohland <ohland@charter.net> - 2026-08-08 09:44 -0500
        Re: -TC on A30 Re: ABIOSDSK.386 "Josh Rodd" <joshua.at.rodd.dot.us@rodd.us> - 2026-08-08 14:55 +0000

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