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Sharp PC-7100: no hard disk drive present

The expansion chassis does not support any DMA mode operations which is required for hard disk operations such as the ones XTIDE would use.
As per my note above I believe it has to do with the maturity of DOS at the time of the unit being created.
Sharp wrote some propietary routines into their version of 2x to support the hard disk.
Someone with the right know-how might be able to reverse engineer those changes and see what was going on - and perhaps adapt this to an XTIDE, but I don't believe this is a realistic outcome.
I have the PC-7100 version which unfortunately had its hard card and socket removed :-(

I'd dearly love to get some sort of hard disk working on it but it seems impossible.
Serial/Printer connected devices are the only hope and even then its extremely limited (I'm using nibble for a PCMCIA parallel port card for example)
 
Can you provide any details on this? I can't get it to recognize over 720kb disks using a Gotek with FlashFloppy and would love to be able to access larger drives.
apologies I didn't log back in for a while

I simply used the hxc utility and created a 2.88mb DD image then drag/dropped files into it
You can do anything except boot from it

It seems if you create a custom/raw image over this amount it will initially work but start to fail as soon as you write to it
 
I could have a look inside mine for the roms, i'm not sure anymore it they are in a socket or not. I have tried to play around with the PC 7100 a lot since the Hardcard in the first one i have died.
I tried installing a NEC V30 to see if a ZIp drive on the printer port could work. But the system just hangs at the BIOS screen with a V30 in it. I tried one of those OPL2LTP sound cards, but it doesn't work on the port. These machines are really strange on a hardware level, at least for a IBM XT Clone.
It's currently running on a gotek with the little trick that lets it use 2,5mb disk images, with the original A drive as a B drive
thanks for this message, you saved me soldering a new chip on.. I was nervous about it :)
Now I will put the V30 in a little frame and look at it instead.. haha
with the floppy i am curious, did you make a molex splitter to run both original and new gotek drive?
I am (very slowly) designing a 3d printed replacement fdd bezel which removes the hdd "grille" and puts a gotek there - will publish to thingiverse when ready.
I found a local (australian) Supplier of beige PLA that is only a shade or two brighter than the existing
 
with the floppy i am curious, did you make a molex splitter to run both original and new gotek drive?
yeah, i have both drives working. I recently went one step further, if you bring out the drive select jumpers to a switch you can change which drive is A or B. This system uses the real Shurgard (spelling?) interface and not the IBM pc way of selecting drives. I don't think the drives can be switched while in use (i haven't tried) but it's usefull if you don't want the Gotek as the A drive.

I've recently tried to use one of those old parallel CF card readers on the Sharp and they work, but are really slow and not always stable (for example, i could load the driver using the Gotek as my booddisk, but not using the normal DD floppy drive)

I've also ordered some of those 8 bit ISA to USB cards, to see if those can work in the Expension chassis.

I am (very slowly) designing a 3d printed replacement fdd bezel which removes the hdd "grille" and puts a gotek there - will publish to thingiverse when ready.
I took out the cover of the CGA port and attached the gotek board in the area where the CGA card should go. a 90 degree USB plug and a small switch stick out the back of the Sharp. I mostly use the gotek as a boot device to load the driver for the parallel port card reader. and switch the gotek to the B drive when the expendsion chassis is connected as that has it's own harddrive.
but, a 3d printed bezel for the gotek would look much nicer.

i do wonder, if the ISA to USB card works, would it be possible to get it working inside the machine. The hardcard that it shipped with is not connected with a regular ISA bus, part of the logic supporting the drive is on the motherboard. I wonder if there is a way around that...
 
The expansion chassis does not support any DMA mode operations which is required for hard disk operations such as the ones XTIDE would use.

There are variants of XTIDE compatible hardware that do not require DMA. For instance, the 8-bit (and very simple to implement) XT-CF-Lite variant just requires an 8-bit I/O port, no interrupt or DMA, driven entirely by polling. If the interface supports a serial or parallel port it should support that type of device.

Does the expansion chassis allow memory devices, particularly any card that requires an option ROM? If it does that then an XT-CF should be possible via that route.
 
I just got the ISA to USB cards, and with a bit of fiddeling they work! i don't think you can boot from the flashdrive, unless the rom socket on the card works with the PC7100. But using Dos 5 this gives a 2 Gigabyte drive that is not really that slow. only the first access of the drive takes a while but after that it works perfectly fine. It's a lot faster then the parallel port devices in Nibble mode.

I can copy stuff to and from the flashdrive, load games from it and the flashdrive can be removed, used somewhere else (to copy something from a modern system for example) and plugged back in without rebooting.

Sadly, but expected, the card don't work in the connector for the original hardcard, so either the expansion chassis is needed or moddification of the hardcard slot to accept the adressing of the USB card (if that is even possible, it's really not my cup of tea to figure something like that out).

The Sharp now boots from a Gotek with the driver on it, and then I can use the flashdrive as a normal harddrive. It works both with the original MFM harddisk (as a D drive) or without it as a C drive. Which is good, as the MFM drives bearings are bad and it doesn't always work.

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