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8 bit IDE (XTA) Replacement Project

Oh, while reading the 19 (!!!) pages you have already written, I forgot the important things I intended to write. Sorry.

For anyone really wanting to experience the nostalgia of the old disks, but all their disks have failed, an emulator could move a real stepper motor the same way as the old disks did. I would think that a failed stepper motor would be really rare. I can see two ways to do this. Either just use the stepper as it is in place on a broken disk. That would require using the track 0 sensor. Unless the broken disks spins, this would most likely guarantee a groove in the platters where the heads would scratch a non-spinning disk. The other way would be to just disconnect the stepper motor from the head movement assembly, and remove the track 0 sensor. That way the stepper can move freely and the disk emulator can just move it without caring for max tracks and whatnot, if that would be desired. This might not create a fully authentic sound as I would think that the head movement assembly forms parts of what creates the classic seek sound.

More interesting, perhaps:
The schematics for the A590 and A2091 I just mentioned are freely available online:
https://archive.org/details/a-590-s...ANUAL_PN-314899-01_1989_AUG/page/n27/mode/2up

And more importantly, the source code is available as part of a leak of the AmigaOS source code a long while ago. I was about to write that I'm not going to link to shady sites, but it turns out that some brave or foolhardy soul have tempted fate by putting it all on github. A company who has some connection to the copyright remains from Commodore put out a "protest letter" against spreading of the leaked code, but people hinted that they only did that because they were contractually obliged to put out a statement if there would be a leak, and all talk has been about the actual OS, and not either ROMs for add-on devices or for that sake add-on software. Here is the source for the A590.
https://github.com/Arquivotheca/amiga-os-src/tree/3.1/os-source/other/harddisk/a590

(And as I said, the A2091 is basically the same thing as the A590. The only differences are the form factor, product name, no power LED for an internal card, a pin header for the disk activity LED (just realized that this might be the reason for some (all?) A2000's having a multi color hard disk LED - perhaps one color is used for XTA activity and the other for SCSI activity), female vs male bus connector, no external power connector for the internal card version, and space to mount a 3.5" disk directly on the card (making it a hard card - this feature was more or less for free as any internal Amiga card anyways need to be super long to both connect to the bus (that sits inside of a passive ISA backplane intended for PC emulator cards) and also have a card slot bracket, in this case for the DB25 for external SCSI).
 
I have an A2091 card in my Amiga 2500, but like all of the ones I've seen, the IDE-XT connector is unpopulated, and it came with a SCSI drive instead.
 
MiaM said:
Another device that uses XTA drives is the A590 external hard disk + memory expansion for the Amiga 500 (also works with the A1000), and the electrically almost identical A2091 internal card for the A2000 (can also be used with the A3000 and A4000 but doesn't make that much sense in those). Btw I'm 90% sure that these have two PCB placements for the XTA header, likley to fit different layout for different drives, but then Commodore ended up only using the same WD drive for all of these so I assume that all had the same placement used.
Click to expand...

Amiga A590 has the option to install XTA or SCSI HDD, and as you mentioned, there is no sense to develop a XTA2SD card for it.

Why does the A590 has 2 XTA connectors on board, but with 100% identical pin description. Ok, I got it. Depending on the location of the connector you can use the connector which better fits to your HDD.

MiaM said:
As for disk size/geometry emulation: How about doing things Gotek style? I.E. have various image files on a FAT formatted SD card, and just have each image hard coded to a certain disk geometry? (Not sure how you would change image, if that would even be desireable, but still). You could probably use any existing 3D print models for front panels intended for the Gotek if there is any desire to be able to switch disk images.
Click to expand...

Images can be easily swapped by software, which I have implemented for the PS2XT2SD version. In total 16 images ( same size ) can be handled on 1 SD-card.
 

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MiaM said:
For anyone really wanting to experience the nostalgia of the old disks, but all their disks have failed, an emulator could move a real stepper motor the same way as the old disks did. I would think that a failed stepper motor would be really rare. I can see two ways to do this. Either just use the stepper as it is in place on a broken disk. That would require using the track 0 sensor. Unless the broken disks spins, this would most likely guarantee a groove in the platters where the heads would scratch a non-spinning disk. The other way would be to just disconnect the stepper motor from the head movement assembly, and remove the track 0 sensor. That way the stepper can move freely and the disk emulator can just move it without caring for max tracks and whatnot, if that would be desired. This might not create a fully authentic sound as I would think that the head movement assembly forms parts of what creates the classic seek sound.
Click to expand...
I watched this video some time ago where someone did something like this - I'm afraid I can't recall precisely what they did - with one of those drives from an IBM PS/2 which had quite distinctive sounds:
 
The latest design of the PS2XT2SD card, built in a IBM PS/1 2011. Could also be used for the IBM PS/2 30.
Can boot directly from HDD e.g. with MS-DOS 6.22. The built in MS-DOS 4.0 is not needed anymore.
Max. capacity of the emulated HDD is 112MB, but can swap by software between 16 images, so total 1,7 GB available, w/o changing the SD-Card.

1756478905821.png

Picture does show IBM PS/1 monitor with dir of 112MB Drive.


1756479015185.png
 
@CallinElvis is there a variant in here that works on Applied Ingenuity's InnerDrive (an Applied Engineering Vulcan Drive clone, I believe) ? The card is in an Apple IIgs, and the drive was dead - WD93048.

I'm totally fine with just removing this card from the equation entirely given its poor performance etc, but if it is cost effective to just replace the drive then I am all ears.
 
looks like we have the XTA bus.

So we can test ist. But we need an image of a HDD with the apple MBR.

I can send you a XTA2SD card for testing.
 
Its likely the InnerDrive doesn't use any sort of partition map in a traditional sense. The ROM on the card is limited to working with certain drives and usually the partition sizes are hard coded based on the drive detected (20MB is typical). ProDOS itself only supports volumes up to 32MB.
 
njroadfan said:
Its likely the InnerDrive doesn't use any sort of partition map in a traditional sense. The ROM on the card is limited to working with certain drives and usually the partition sizes are hard coded based on the drive detected (20MB is typical). ProDOS itself only supports volumes up to 32MB.
Click to expand...
This was an Inner Drive 40, but yeah, likely hard coded in ROM.
 
ok, that declares why HDD image file found in the internet from the apple iigs are 32 MB , C/H/S 771/5/17, the 40MB WD93048-X drive has 977/5/17, so not all cylinders are used.
 
Well, with the dead drive and better controller options available, i decided to sell the controller card to someone who needed to repair their system. Very cool project, and I may end up circling back in the future :)
 
@CallinElvis Its likely the ROM divides 40MB drives into two 20MB partitions. The Apple II itself has no concept of partition maps. Its up to how the card vendor decided to split drives up.
 
The XTA2SD card in the newest low cost version with a Pi Pico instead of the teensy 4.1.
The size of the card is about 51 x 74 mm, so it can be directly put in the XTA connector ( on the picture left ) or used with the ribbon cable.
Its called the XTA2SDPiC for the Pi Pico ( type C ! ) used.
Further optimizations have been made to minimize electronic parts.

1769104072822.png


Writing and Reading speed is tested with the James Pearce Disktest, results are shown on the picture.

1769104126037.png
 
How do those speeds compare to an old, clunky, physical drive?

Also, I’m sure it’s in one of the previous 20 pages, but how do we order one of these?
 
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