Raspberry PI SCSI emulator

[Amiga1992]

Originally Posted by Pat the Cat

one advantage of a Pi zero is, it has far less hardware to take care of

That takes the cake for the most ignorant thing you said in this thread.

This project is not an "ambitious WIP", you can build your interface and download the software and use it now. On the X68000. There's nothing to be skeptical about, the system works.

Why do I even bother replying to your nonsense once again? Ugh.

[Pat the Cat]

Originally Posted by Akira

Why do I even bother replying to your nonsense once again? Ugh.

For the times when I'm at least half right?

Anyway, fair enough, Amiga SCSI networks are not new.

"Set me as a seal upon thine heart, as a seal upon thine arm: for love [is]
strong as death; jealousy [is] cruel as the grave: the coals thereof [are]
coals of fire, [which hath a] most vehement flame."

http://aminet.net/package/docs/misc/NettVerk

[idrougge]

Originally Posted by Pat the Cat

Usually not, but there are exceptions. Some controllers come with neither a 25 pin nor a 50 pin header, but a 36 pins Centronics connector for an external SCSI drive.

That's what commonly called a printer. Good luck using your printer as a SCSI controller.

Originally Posted by Pat the Cat

Some 50 pin connections do use extra pins, for 16 bit wide SCSI access. Again, that's why I posted the link, so people could check.

No they don't. Stop spreading misinformation. Stop speculating about things you don't know the first thing about.

Originally Posted by Pat the Cat

The cause of my concern is HOW WELL IMPLEMENTED the SCSI commands are. Typically an 8 bit SCSI device does not bother, and I respectfully point out that this appears to be a "work in progress" rather than "click here to buy on this website.

Go ahead and dig up a 16-bit SCSI controller for the Amiga.

Originally Posted by Pat the Cat

Actually quite a lot of Amiga and other SCSI controllers simply force 8 bit SCSI if any devices are 8 bit. Connect an 8 bit device to the outside of an Amiga, all the devices inside also get slowed down by 8 bit access.

Go ahead and dig up a 16-bit SCSI controller for the Amiga.

Originally Posted by Pat the Cat

The Amiga doesn't care, but the user does, if they spent money getting fast controller and then blame the Amiga when a "new" SCSI device makes their drive access slow.

Amiga owners with a wide SCSI controller won't resort to a home-made Raspberry Pi contraption. And they don't need your help.

Here, have a read: http://www.wonkity.com/~wblock/SCSI/SCSIExamples.html

[Zetr0]

@Thread

Sorry Pat, there is a lot of incorrect information about Amiga and SCSI in general there sir. It's easy to get turned about in SCSI land, I remember my first year working with industrial SCSI arrays and systems in Industrial land - that is an eye opener and steep learning curve thats for sure.

Sadly a lot of miss-information about SCSI is propagated on the web in general - its not an ART as some say it is a very simple and exact science you just need to approach it properly (almost as if you are setting up an IPX network )

Have a read here chap this will get you up to speed - I have posted some some articles on here and AmiBay about SCSI and DMA SCSI on the Amiga and I would humbly suggest having a look at the ABLE SCSI project for the Amiga (it should be on aminet.net) - it will take your knowledge to the next level -

This way my friend we can have a discussion on the method and Protocols thats are emulated by the RPi to throw data to and from the SD Card via the SCSI BUS - also (TCP/IP over SCSI) excites me a lot -

Sadly with some of those statements posted while were discussing Narrow / Wide implemented SCSI 1 / 2 protocols (and their conjunctions) - it kinda seems you are arguing the colour of a blue crayon.

So read some of those links bud, come back fresh and lets have a real discussion on how this could / would be implemented within an Amiga SCSI host =)

[Pat the Cat]

Originally Posted by idrougge

Go ahead and dig up a 16-bit SCSI controller for the Amiga. Good luck connecting your SCSI device to the parallel port

Are people in the habit of burying them? Funilly enough, some people did indeed think connecting a SCSI device to an Amiga parallel port was a good plan.

http://amiga.resource.cx/exp/paradox

Fascinating link Iggy. Author clearly didn't know how you can attach 16 bit and 8 bit devices to the same cable and controller (3 terminators in the chain, but number 3 just masks off the extra 8 bits of data on the 50 pin ribbon cable from the 8 bit devices beyond it. Not a hack.

https://en.wikipedia.org/wiki/SCSI_h...te_termination

But hey, never can happen on an Amiga, right? You are saying there are no 16 bit SCSI controllers on the Amiga. Potentially, more than you might think. Try plugging in an FAS216U to an Amiga controller with a standard FAS216 based controller...

http://ps-2.kev009.com/ohlandl/SCSI/..._datasheet.pdf

You might also get some joy with the expansions based on the NCRC94, such as the Flyer. 16 bit internally, but AFAIK Amiga implementations do not use 16 bit 50 pin SCSI cables, except as 8 bit 50 pin SCSI cables.

I would strongly urge SCSI card owners to look up their card, controller chip, and upgrade potential and make their own minds up, rather than relying on flame warriors who have used less than a dozen different Amiga SCSI controllers, and who simply "believe" that Amiga SCSI can only ever be 8 bit except with a Phase 5 product or a Warp Engine. Even a humble WD33C3 controller can sometimes do up to 10MB second synchronous transfer, but sadly most A1200 Blizzard SCSI kits are limited to SCSI one speeds. Tough.

http://amiga.resource.cx/search.pl?product=SCSI

Jope, good luck, the drive side should be OK at least.

[Locutus]

I dont want to reply to this, but just...

[Pat the Cat]

Originally Posted by Zetr0

@Thread

Have a read here chap this will get you up to speed

Some people used 2 50 pin cables to do 32 bit transfers over a bus, but never on Amiga. Useful link there though for Daedalus to look up differences in Command Set from SCSI-1 to SCSI-2.

Better link concentrating on how parallel SCSI and a separate link to connector standards here. Still far from perfectly accurate though.

https://en.wikipedia.org/wiki/Parallel_SCSI


https://en.wikipedia.org/wiki/SCSI_connector

[Daedalus]

Originally Posted by Pat the Cat

Needs 2 50 pin ribbon cables in order to work? This is a joke, right?

Comprehension fail.

Edit: In what is an extremely rare occurrence, it appears Pat has realised he made a mistake and corrected it by deleted that line from his post.

Useful link there though for Daedalus to look up differences in Command Set from SCSI-1 to SCSI-2.

*yawn* You're still mixing up connector type with SCSI type, and once again refusing to do anything about your ignorance. Come on Pat.

[thgill]

I'm sure all the high end Toaster users are chomping at the bits to use this.

[Pat the Cat]

Originally Posted by thgill

I'm sure all the high end Toaster users are chomping at the bits to use this.

Toasters do not have SCSI ports.

Flyers do, but they require a certain speed of device to work properly. Which could be an issue or the device might make the grade. Doubtful but it remains to be seen.

[Pat the Cat]

Originally Posted by Daedalus

Comprehension fail.

Edit: In what is an extremely rare occurrence, it appears Pat has realised he made a mistake and corrected it by deleted that line from his post.


*yawn* You're still mixing up connector type with SCSI type, and once again refusing to do anything about your ignorance. Come on Pat.

I respectfuly note the time of my post as proceeding your post.

Yes indeed, as wel as an extended command Set, SCSI-2 also specifies extra pins for things like reselect signal.

This is has been the problem for 30 years, people thought "SCSI compatible so it works, no problem" without considering how better, faster storage could be done with right devices, right cabling, right terminators.

[Zetr0]

@Pat_the_Cat

I do enjoy your enthusiasm - its refreshing when some one "go's at it" instead of wombles about the place =)

Originally Posted by Pat the Cat

... You might also get some joy with the expansions based on the NCRC94, such as the Flyer. 16 bit internally, but AFAIK Amiga implementations do not use 16 bit 50 pin SCSI cables, except as 8 bit 50 pin SCSI cables.

Now, at a risk of digressing the thread further - I am curious as to why you believe this is the case - what evidence do you have to suggest this?

[Pat the Cat]

Actual chips used NCR53C96. Observe closely that both rows of each SCSI connector has pins connected.

Yet according to some, half of the 50 pin connector on SCSI 2 controlers were always grounded. Never connected. No change at all from SCSI-1 to SCSI-2 cables. Not that SCSI ever formally defined connections.

http://amiga.resource.cx/photos/phot...res=hi&lang=en

It's no wonder SCSI-2 is described as "obsolete". Even for people making genuine 16 bit SCSI bus controllers, the moment somebody plugged in an external drive, the whole lot ran at the slower bus rate. People making devices that could talk at higher speeds always had the devil's own time demonstrating that it actually did so unless plugged into a suitable controller.

I guess the real acid test would be a solid state card box, with a 50 pin and 68 pin connectivity, that actually had a screen that displayed what sized data bus it was currently using. Also the throughput data rate, that would be nice.

It's not going to happen with this device, but a Hat might be doable.

Tricky part is getting it visible from inside a case... er...

[ptyerman]

Oh man! Another thread filled with crap and misinformation. Where does it end?

[Daedalus]

Originally Posted by Pat the Cat

Actual chips used NCR53C96. Observe closely that both rows of each SCSI connector has pins connected.

I see a number of lines connected. Perhaps they were convenient vias to route a ground trace from. Notice particularly how most of the pins you're talking about are on the bottom rows of the connector (the ground pins), and are routed straight to the decoupling capacitors for nearby ICs. But of course, you're a "board-level hack specialist" or something, so you already saw that.

Yet according to some, half of the 50 pin connector on SCSI 2 controlers were always grounded. Never connected.

There's an extremely important difference between not connected and grounded that you appear to miss there. Anyway, what I actually said was:

"half the conductors on the 50-pin SCSI-I and SCSI-II ribbon cables aren't active"

I didn't say they weren't connected. They're all ground except for one, and are used for shielding and isolation purposes on long ribbon cables, similar to ATA-66 cables.

No change at all from SCSI-1 to SCSI-2 cables.

That's right. The bus speed changed but the connector stayed the same except for the 16-bit SCSI-II *Wide*, which uses a totally different connector to accommodate the extra bits.

Not that SCSI ever formally defined connections.

True, but there are several common standards, otherwise you'd never get anything to talk to anything. 50-pin IDC ribbons are one of them that applies to SCSI-I and SCSI-II drives.

the moment somebody plugged in an external drive, the whole lot ran at the slower bus rate.

Only for people connecting 8-bit SCSI-I or SCSI-II devices to 16-bit SCSI-II *Wide* or SCSI-III buses, which have totally different connectors. Such setups are rare as standard since external connectors exist for these buses and so they are used instead. Adaptors are needed to convert the bus to 8-bit, so if you're buying such adaptors, you surely know what you're doing.

I have a SCSI-II setup here now. It runs at 10MB/s. If I connect and external drive, it runs at 10MB/s. Absolutely no effect on performance.

People making devices that could talk at higher speeds always had the devil's own time demonstrating that it actually did so unless plugged into a suitable controller.

Obviously, but they're pretty foolish if they're trying to demonstrate speed on an incapable controller. Just like how hard a time you'd have trying to demonstrate the speed of a USB 3 hard drive by plugging it into a USB 1 host. People understand that. SCSI isn't voodoo; it might be more complicated and confusing than IDE, but shouldn't be beyond anyone even remotely technical once the bus requirements of the device are specified.

[idrougge]

Originally Posted by Pat the Cat

Are people in the habit of burying them? Funilly enough, some people did indeed think connecting a SCSI device to an Amiga parallel port was a good plan.

http://amiga.resource.cx/exp/paradox

Is that your legendary Centronics 36-pin SCSI?

Originally Posted by Pat the Cat

Fascinating link Iggy. Author clearly didn't know how you can attach 16 bit and 8 bit devices to the same cable and controller (3 terminators in the chain, but number 3 just masks off the extra 8 bits of data on the 50 pin ribbon cable from the 8 bit devices beyond it. Not a hack.

https://en.wikipedia.org/wiki/SCSI_h...te_termination

As usual, you're speculating. Whether the author knew or did not know is not something you can discern, and what you describe is common knowledge — common knowledge which makes some of your earlier statements even more pointless.

Originally Posted by Pat the Cat

But hey, never can happen on an Amiga, right? You are saying there are no 16 bit SCSI controllers on the Amiga. Potentially, more than you might think.

I never said that there aren't 16-bit SCSI controllers on the Amiga. I'm just not lucky enough to own one, like the vast majority of Amiga owners who would consider using this solution.

Originally Posted by Pat the Cat

Try plugging in an FAS216U to an Amiga controller with a standard FAS216 based controller...
http://ps-2.kev009.com/ohlandl/SCSI/..._datasheet.pdf

If you've plugged a FAS216U into a Fastlane Z3 or Blizzard SCSI kit, do report your findings. I suppose your data bus magically widened at the same time.

Or rather, I suppose you're doing your usual thing: speculating, spreading misinformation and derailing.

Originally Posted by Pat the Cat

You might also get some joy with the expansions based on the NCRC94, such as the Flyer. 16 bit internally, but AFAIK Amiga implementations do not use 16 bit 50 pin SCSI cables, except as 8 bit 50 pin SCSI cables.

Exactly. Again, I suppose this has been a big problem for you in your Amiga using life?

Originally Posted by Pat the Cat

I would strongly urge SCSI card owners to look up their card, controller chip, and upgrade potential and make their own minds up, rather than relying on flame warriors who have used less than a dozen different Amiga SCSI controllers, and who simply "believe" that Amiga SCSI can only ever be 8 bit except with a Phase 5 product or a Warp Engine. Even a humble WD33C3 controller can sometimes do up to 10MB second synchronous transfer, but sadly most A1200 Blizzard SCSI kits are limited to SCSI one speeds. Tough.

I would strongly urge SCSI card owners to pay no respect to your speculations and go on with their lives, asking someone knowledgeable like Daedalus in case they have questions about how wide their SCSI bus is or how to set it up.

Originally Posted by Pat the Cat

http://amiga.resource.cx/search.pl?product=SCSI

There you go, please list all the 16-bit SCSI controllers you find there.

[Mr.Flibble]

I have a ZiLOG Z53C8003...

[idrougge]

It has now been confirmed working on Raspberry Pi 1B as well.

[Locutus]

Using what system on the other end? x68k still?

[idrougge]

Naturally.