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Astra "The One" Drive"

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Thanks for the info Avery, the initial post was more of a joke as I'd read what Nezgar etc said about how it was just a basic drive with no 'abilities' so I never really thought of it as a needed contender for adding but its great to know that you check out every little nook and cranny about emulation. Thank you for doing that, its shows in the emulator and we really appreciate the extra mile you go.

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You can already emulate this drive as it appears to be a clone of the PERCOM RFD-40S1. The ROM is 99% similar with slight optimizations and fixes, and there is some unused space at the end that contains leftover fragments from the RFD-40S1's ROM. As a clone, it has no high-speed support, no code upload, and no special commands, but it does of course support the PERCOM block commands.

 

The differences from the RFD-40S1:

  • Minor optimizations to save space: removing an unnecessary push/pop, changing long branches to short branches, and using 8-bit displacements instead of 16-bit displacements.
  • Step rate has been slowed down from 12ms to 20ms.
  • There was a bug fix to the FDC error handling, presumably for improved copy protection support. The RFD-40S1 ignores deleted sectors, while the Astra 1001 properly detects and returns them as errors.

 

Hah, wow, I never even thought of just trying it in Altirra, nice! Thanks for your insight.

 

Really interesting that it is so similar. With the Astra drives coming out so late in the game (1986) It makes you wonder if it was a legitimate derivative authorized by Percom, or if they just had lots of time to reverse engineer and customize it a little.

 

Does this ROM support a double sided mech with the right PERCOM commands? 2 mechs?

 

It would be interesting to compare a dump from "The One", which shipped with two double sided mechs. I saw someone post they had one recently, I guess I'll persue that.

 

I guess the MPP printer chip could basically operate independantly of the rest of the drive controller hardware, just tapped onto the SIO bus.

 

Also reminds me i need to dump the ROM from my PERCOM AT-88-S1 with double density upgrade to compare. I noticed my percom drive's step rate appears configurable via the PERCOM block, because from powerup its slower, and after formatting a disk with SDX, it is faster. I haven't dug into it further than that.

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Both the PERCOM and the Astra firmware support four drives and two sides. The relationship is odd. It's clear that the PERCOM firmware is earlier, as the Astra firmware has a fragment of it at the end. However, the Astra firmware was clearly reassembled, as all routines were repacked and some inconsequential instructions were optimized with 8-bit displacements. It would make sense for Astra to have licensed the firmware, but if they were able to reassemble it I'm not sure why it would have included bits of the old ROM.

 

The step rate is indeed configurable, as the PERCOM block is essentially the raw drive state block in drive RAM and includes the step rate value. That's also the reason for the weird 0/4 density value -- bit 2 of $D018 is the hardware bit that controls the double density input to the FDC. Same for the swapped byte order, since the 6809 is big-endian.

 

Astra firmware disassembly attached. Parts that are different from the Percom RFD-40S1 are marked with <!>.

 

astra1001.s

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Hello Avery

 

Does that mean you can put the Astra ROMs in a Percom drive"?

 

Sincerely

 

Mathy

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Does that mean you can put the Astra ROMs in a Percom drive"?

 

Aside from perhaps a pin compatibility issue with the physical ROM chips, the firmware is so similar I don't see why the Astra firmware wouldn't work in an RFD-40S1.

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I'm curious to find some more Percom ROM dumps now... there is reference to Percom ROM updates, so it's possible this ROM was of Percom origin. If we get a few more Percom ROMs dumped to compare, and find this code in someones Percom drive that would confirm things... There are some references that Percom did have updates to their firmware:

 

http://www.verycomputer.com/10_62ab164454e9ee08_1.htm

"...even gone to the extent of purchasing an upgrade rom in 1986 or so..."

" I ordered and installed a newer rom to correct some problems."

 

Looking at a few Percom PCB's looks like they used a 2?32 EPROM not 2516 like the Astra 1001, so if it only uses 2KB of the 4KB if the larger EPROMs were easier/cheaper to come by...

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You are becoming a mini Drive Preservation Project Nezgar, and its great to see even if its not meant to be that, I may never use a lot of these drives even if they are available via emulation or lucky enough to have the real thing but for someone to attempt to database them and bringing back the history of them is just such a good cause.

 

There's always someone who will like the info and a source, good luck with all that...

 

Paul.

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It's good to know the best roms and why for FDC, I am interested in seeing the bet fixes applied from one to another as well. Cool stuff.

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You are becoming a mini Drive Preservation Project Nezgar, and its great to see even if its not meant to be that, I may never use a lot of these drives even if they are available via emulation or lucky enough to have the real thing but for someone to attempt to database them and bringing back the history of them is just such a good cause.

 

Thanks Paul, yes I do seem to have an interest in 'preserving' disk drive ROM's :) Even more rewarding is leaning on the vast knowledge of these forums (especially Phaeron in this case!) to dissasemble the code and reveal new historical insights. (and of course raise more questions heh) This Astra drive running Percom firmware was a complete surprise. But also thanks to 19Echo on facebook for entertaining my request to desolder and dump the ROM!)

 

I'll ride the train as long as the interest lasts, and hope to find more in my travels. One of these days I'll get a website off the ground to organize these findings...

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