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Problem with FloppyEmu

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53 minutes ago, Dog Cow said:

The SE ROM is 256KB. The Plus motherboard can address up to 256K of ROM, so let's see what happens! But I bet the SE ROM is going to want ADB, which we know the Plus doesn't have.

Maybe we can use the same hook-and-patch mechanism to solve that problem? It would be a very interesting experiment indeed.

 

c

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17 hours ago, Paralel said:

Unfortunately, as far as I am aware, AEHD+ are rather rare.

 

I don't think anyone on this forum that is active actually has one.

I have a AEHD+, my opinion is that they are not rare.  While it does support Macintosh 1.44 disks, the main reason to have one back in the day was for compatiblilty with PC formatted disks.  Using AEHD+ you can not boot from a 1.44 disk on a older non-FDHD mac.   

 

I also have a couple of floppyEmu's, and I disagree with the title of this thread, the fact that older Mac's do not support MFM disks is not a "problem" with the floppyEmu.   The floppyEmu emulates a floppy disk and drive at a hardware level, it works very doing this.

thank you,

Rick

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17 hours ago, Gorgonops said:

 I have other issues with this. If that board really just has the components you say and *doesn't* have some sort of microcontroller on it then I can't in the slightest wrap my head around why it has a ROM chip on it. (Part of a state machine that initializes the serial chip into a hardcoded transfer mode without needed a CPU?) How fat of a connector this to the main board? (Seriously, there don't seem to be *any* pictures of the guts of these things online.)

 

28 pin interface back to the logic board.   I don't know how the pins are used or even if they are all used.   28 pins for the external floppy, which uses essentially the same interface board.    44 pins or some such on the internal connector.   Whatever an IDE hard drive + power connectors would use.

 

Also, that 28 pin external cable/interface is used both for the external floppy and the external SCSI adapter (one or the other).   Both boards have an 85C30 at the input end, facing that 28 pin connector.    The SCSI adapter pretty much just has a 53C80, and a GAL in addition to the 85C30.  I can't remember if it also has a flash.   I should check my notes at home.

 

I've always assumed that the ROM is there as a simple logic translation device.    If I  have an input of 12 give me an output of 4F.    That kind of thing.   Again, would need to create a schematic for more information.

 

Yep, no pictures on line that I've ever seen.  Next time I did one out I'll take some photos.   I wish I still had a scanner.   Scans of circuit boards on a flatbed have always turned out better than my photography efforts, even when I remember to put the camera in Macro mode.

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18 hours ago, Gorgonops said:

The Outbound only uses Plus ROMs, not an actual Plus motherboard, correct? I can't find any pictures of its innards, is it possible that the 85C30 *is* actually the comm port controller, they just punted it over to a peripheral controller board that also has the floppy controller on it?

 

Correct.  The Outbound has it's own circuitry.  Not a Plug logic board in there.   Also, one could use either Plus or SE ROMs.  

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41 minutes ago, trag said:

The SCSI adapter pretty much just has a 53C80, and a GAL in addition to the 85C30.  I can't remember if it also has a flash.   I should check my notes at home.

Weird. I'd love to know exactly what lines are defined on the interface cable. It seems like weird overkill to use 85C30s as a serial data pump instead of just using an 8-bit bus over such a short cabling distance, especially when they're using a 28 pin connector.

 

51 minutes ago, trag said:

I've always assumed that the ROM is there as a simple logic translation device.    If I  have an input of 12 give me an output of 4F.    That kind of thing.   Again, would need to create a schematic for more information. 

Another thing it could be doing is handling the GCR translation table in hardware for 800k disks, although you definitely don't need a 64k ROM for that and that would also be a weird overkill considering the normal Mac floppy driver for a Plus/SE/whatever does that in software. (The IWM really isn't much more than a glorified UART.) If they are using the 85C30 as a data pump maybe they could be using a weird little state machine in the GAL to clock in the necessary programming register contents on reset?

But, yeah, it could strictly be acting like a PLA. A ROM that big plus a cleverly programmed GAL could do any number of things, pretty much up to and including acting like a simple MCU.

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5 hours ago, lisa2 said:

Using AEHD+ you can not boot from a 1.44 disk on a older non-FDHD mac.

And that settles that.

5 hours ago, lisa2 said:

I also have a couple of floppyEmu's, and I disagree with the title of this thread, the fact that older Mac's do not support MFM disks is not a "problem" with the floppyEmu.

Ironically it looks like the OP never came back to explain further what his problem really was. I wonder if he was just trying to use diskcopy 6 images instead of 4.2 or RAW. (Or something similar.)

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2 hours ago, trag said:

85C30

I guess the one other thing I'd throw out there: are you absolutely certain that was the chip model number? Realistically all the confusion would evaporate if it was actually, I dunno, something like a Z8 family MCU with a similar part number.

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4 hours ago, Gorgonops said:

 you definitely don't need a 64k ROM for that and that would also be a weird overkill considering the normal Mac floppy driver for a Plus/SE/whatever does that in software.]

 

Remember, it's 64 Kbits.    While probably still overkill, it may have been the smallest thing economically available at the time.

 

And yes, definitely the SCC chip.   85C3008 specifically, IIRC.

Edited by trag

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