SCSI Progress At Last

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flynnjs
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Re: SCSI Progress At Last

Post by flynnjs » Wed Oct 05, 2011 6:47 am

Erm, I've got no idea whether the AIV SCSI board is supported with Discs.
Anyone know?

Hint taken, I've got enough interested parties to do a run of boards now
so I'll get them submitted into the board house this week regardless.

Jason

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Re: SCSI Progress At Last

Post by johnkenyon » Wed Oct 05, 2011 4:43 pm

flynnjs wrote:Erm, I've got no idea whether the AIV SCSI board is supported with Discs.
Anyone know?
From what I can gather (looking at the AIV and "host adaptor" schematics), the following changes would be needed to make ADFS talk to an AIV adaptor:

Software fixable differences:
1) Change all I/O accesses from FC40-FC43 to FE80-FE83
2) Data (D0-D7) sent to the SCSI bus is not inverted by the AIV adaptor
3) Status byte D2: Tied to 0 (old), reflects state of SCSI RST pin (AIV)
4) Status byte D4 (IRQ state): IRQ (old), nIRQ (AIV), (i.e. inverted)
I guess D4 is used to by the IRQ handler to see if it was raised by the SCSI adaptor or elsewhere.

Hardware differences:
1) Data sent to the SCSI bus uses tri-state buffering (AIV) compared to gated open collector outputs (old).
2) The timing of the SEL signal may be different, as the AIV uses an RC network to slow the rise time of the BSY signal.
(fixed by removing R2 and C3)
3) The ACK signal generation is the same basic design, but implemented differently, (two diodes and a pullup resistor to combine the read data and write data select signals, instead of a NAND + inverter)
4) SCSI Pin 34: AIV = terminated by a 330R/220R resistor network, "old" = tied to +5v. Note that from what I've found on t'interweb, where everyone says that this pin is "GND".

So in short, no it won't work with hard discs "out of the box", but it should be able to modify ADFS 1.50 to play ball.

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Re: SCSI Progress At Last

Post by johnkenyon » Fri Oct 07, 2011 11:03 am

johnkenyon wrote:
flynnjs wrote:Erm, I've got no idea whether the AIV SCSI board is supported with Discs.
Anyone know?
Update.
Note that all this is "in theory", and based on JGH's ADFS 1.50 disassembly...

To turn an AIV SCSI adaptor into an almost ADFS compatible adaptor:

Hardware changes:
1) Replace IC1 (74AS373) with a 74AS533 (to invert data out)
2) Cut track to IC3 pin 7, install link IC3 pin 7 to IC3 pin 14. (Ties D2 of the status bit to "0")
You can try leaving (2) out, but the code to check the status needs to read the same value twice before it returns.

Edit the ADFS 1.50 ROM:
1) Change all I/O accesses from FC40-FC43 to FE80-FE83
2) Change the CMP #&F2 to CMP #&E2 at ROM location &AB91 (to allow for inversion of b4 (IRQ) in the status register.

Note that (2) is the only code in the ROM which looks at the whole status byte - bit masks are used everywhere else.

/john

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Re: SCSI Progress At Last

Post by BeebMaster » Mon Oct 10, 2011 7:03 pm

This has reminded me - is there a version of Acorn ADFS which supports a second Winchester controller mapped at &FC44-47 or thereabouts?

Whilst doing a recording session with the Digistore over the weekend, I finally realised why ADFS doesn't detect the Digistore: the host adapter board inside the Digistore is bodged to make it appear as the second Winnie controller. I found this out by accident after adding a hard disc.

The idea was to attach one of the Seagate SCSI discs I'd formatted in an earlier bit of this thread to the Digistore to try out a restore operation. (I'd already done a backup operation with the Acorn Winchester Disc 130 a couple of weeks back when I finally got the Streamer ROM sorted out, but I didn't have anything to restore to).

I didn't want to go to the trouble of rigging up a whole Winchester setup, so I thought that changing the ribbon cable for one with two sockets would allow me to run the Seagate disc and the Digistore's tape drive off a single host adapter board.

Nothing happened - ADFS wouldn't detect my Seagate disc, but when I did *STREAMER UNLOAD, it ignored the tape drive and shut down the hard disc instead!

So then I guessed that the Digistore's host adapter was mapped to the second Winchester controller memory locations and, sure enough, taking the board out and looking at the solder side revealed a cut track and a short length of wire around the area of IC 6, carrying out exactly the same function as the jumper on the modified host adapter board published in the "Hard Drive 1.2" document.

I was also expecting the ribbon cable to melt with the modern SCSI drive connected up, due to the famous "pin 34" problem, so I was a bit surprised when it didn't. I looked a bit more closely at the Acorn host adapter board in the Digistore to see that the track which connects to SCSI pin 34 had been drilled through and filled in! So the Acorn 5V pin 34 issue was known about as long ago as 1984!
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Re: SCSI Progress At Last

Post by george.h » Wed Jan 11, 2012 7:56 pm

Oh boy oh boy oh boy!

While having a bit of a clear out (aka a rummage through the bottom-less pit that is my storage cupboard I came across my 1st DDS-1 2GB DAT drive in it's external 3.5" case. Twas then I had one of those "Aha!" moments.

So I've finally stripped out the DAT drive and replaced it with my SCSI drive which I'd been experimenting with many many moons ago. Some double sided foam pads secured my Akhter host adaptor to the top of it, then case back on. I obviously got further than I remember as, joy of joys, ADFS mounted it and it had the usual ADFS Library and Utils directories, plus a DR-DOS 20MB drive set up on it.

Obviously last time I must have frigged the Viglen 56MB winchester formatter to format it (after changing the sector size to 256 bytes) as it reports as 56MB. Time I got round to doing that properly and using the max that ADFS will allow (it is a 1GB drive). Anyway, now just to do some pics to post on here and find my work floppy with the programs I knocked up during my initial investigations to change the sector size so I can see if I did the mode change as well...

Me one happy bunny with a Master 512 with working hard drive!
Hehehehe :D :D :D
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Re: SCSI Progress At Last

Post by BeebMaster » Sun Jan 15, 2012 1:37 pm

Great news! It will be interesting to know if you had to go through all the Change Definition business or whether the drive you have is one of the few that the Beeb will support without any faffing!
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Re: SCSI Progress At Last

Post by george.h » Tue Jan 17, 2012 11:35 am

No luck finding the floppy with my original progs on it, so I'll have to write another set of SCSI utils again (good practise!). When I get them written I'll post the results plus the paramter pages from the drive.

I know that everything I did to get it working was done on my Master, not having an Archie LOL.

Should be more fun this time round now that the host adaptor and drive are in a case......

[edit]
I've came across some of my drunken spider notes from back then and the two main changes I made to get it working were :

1. Use Mode Select to change the block length from 000200h to 000100h, i.e. change the sector size from 512 to 256 bytes. I then had to initiate a low level format.

2. This is the one that really had me flumoxed for a while. At first after a reset (power on or hard BREAK) the drive would stubbornly sit there with a Check Condition status and ignore everything until I issued a Request Sense command. Since ADFS doesn't do this, I had to do this manually every time. After that it would work and ADFS could talk to it, even through at that point I hadn't figured out formatting it under ADFS. To fix this I had to change a bit on page 0 (Unit Attention Parameters) of the Mode Sense Pages. Basically I had to change bit 4 in byte 2 from 0 to 1. This controlled the drives Unit Attention behaviour so that the drive no longer sits there in Check Condition state waiting for a Request Sense command after reset.

More as I re-learn it.... :wink:

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Re: SCSI Progress At Last

Post by BeebMaster » Tue Jan 17, 2012 9:22 pm

Very interesting, I know about the mode select business for 256 byte sectors but I had always had the difficulty that ADFS wouldn't even talk to the drive to be able to send it a mode select command till I was told about the need to alter the drive's operating definition.

Most of the time nothing happens when you type *ADFS or press BREAK with ADFS selected: I will have to look into whether ADFS will talk to the drive if a Request Sense command is sent. I wonder if this, and the Unit Attention params, might be a different issue to the Operating Definition issue, though - what is the make and model of the drive you are using?

I have quite a few older SCSI drives which are either SCSI-1 or can be jumpered to operate as SCSI-1, which don't respond to ADFS, so I will have to try a Request Sense on those to see if it brings them to life.
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Re: SCSI Progress At Last

Post by george.h » Tue Jan 17, 2012 9:48 pm

It is a Seagate ST31230N - though I think I'll have to do some fault finding on my Akhter host adaptor. I just powered it on to do some playing after taking some pics when smoke started comming from the 7438to the left of the SCSI termination resistor packs! I've replaced it but something else must have died to kill it. The drive spins up etc but ADFS hangs when I try to mount the drive.
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Re: SCSI Progress At Last

Post by george.h » Tue Jan 17, 2012 9:59 pm

Some pics as promised (before it started smoking!) :cry: :?
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Re: SCSI Progress At Last

Post by BeebMaster » Tue Jan 17, 2012 10:14 pm

george.h wrote:It is a Seagate ST31230N - though I think I'll have to do some fault finding on my Akhter host adaptor. I just powered it on to do some playing after taking some pics when smoke started comming from the 7438to the left of the SCSI termination resistor packs! I've replaced it but something else must have died to kill it. The drive spins up etc but ADFS hangs when I try to mount the drive.
Oh my word! Don't blame me...

...although I've never had that happen to an Akhter board, I did accidentally put 12V through mine which necessitated all the ICs being replaced...
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Re: SCSI Progress At Last

Post by BeebMaster » Tue Jan 17, 2012 10:18 pm

george.h wrote:Some pics as promised (before it started smoking!) :cry: :?
Very nice pictures, I hope the board isn't damaged too much!

These Seagate drives are the best type to use with Beebs I think, they support 256 byte sectors and the change definition command. You might have been lucky with it being set to SCSI-1 operating definition already, or you might have found an alternative way of getting the Beeb to recognise it with the Request Sense/Unit attention business.

I think I have the same model, or very similar, so a bit more experimentation is on the cards I think.
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Re: SCSI Progress At Last

Post by george.h » Tue Jan 17, 2012 10:22 pm

Oh my word! Don't blame me...

...although I've never had that happen to an Akhter board, I did accidentally put 12V through mine which necessitated all the ICs being replaced...
Don't fret, I'll only be blaming myself, thought I'd appreciated if you could sent that fire engine round for a bit! :lol: :lol:

I think I'll have to check I've not got any wiskers of anything (maybe from the screw holes) that have dropped onto the PSU and sent 12v through the 5v line.... It is going to be nervous few days while I get it fixed...
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Re: SCSI Progress At Last

Post by BeebMaster » Tue Jan 17, 2012 10:54 pm

There wasn't much of an effect when I killed my Akhter board, the power cable started to melt and there was that zzizzing noise but nothing much else.

For all the alleged disasters which have been attributed to me over the years, I've never had a smoking IC - I've had the odd EPROM window flash when I've put one in the wrong way up but that's about it!

I wonder if the drive casing had come into contact with the board, that's always a danger in these Winnie setups. If I have to have things like that stacked up (which I do quite often because they only give you a 2-inch cable!) I usually separate things with place mats or sheets of card. Mind you, that's mainly because I never box things up properly as nothing ever seems to get finished!
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Re: SCSI Progress At Last

Post by george.h » Wed Jan 18, 2012 9:53 am

I've had the odd EPROM window flash
:lol: I've done that too! You first think "WOW! That's cool" - then it sinks in and you think "Oh b*ll*cks!". At least we know where the term FLASH ROM came from :?

The good news is that I've fixed it! :D

I gave the casing a good clean out and came across the odd wiska of metal, so that is still the favourite to point the finger at. The problem this time was my eye sight! Note to myself : next eye test ask about bifocals. After extracting the remains of the "cooked" DM7438, I reached into my box of TTL spares (where I'd previsously checked I had a couple of DM7438 in stock), pulled out the DM74xx chip from the end of the row where the spare '38s were and soldered it in.

Of course if I'd been a bit cleverer (or is that less senile :? ) I'd have given it a less cursory glance to check it was a DM74xx from my box of mostly other makers TTL and used a magnifying glass (boy how the eye sight goes with age :shock: ). Then I'd have spotted that I'd picked the end chip from the row NEXT to where the '38s where and not soldered in a DM7413 :oops: #-o :roll:

Top Tip : Don't replace a 7438 with a 7413 and expect it to work.... [-X

:lol: :lol: :lol: :lol:
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Re: SCSI Progress At Last

Post by IBM portable PC » Wed Nov 14, 2018 1:02 am

Here's a new option. Use a Raspberry Pi as a SCSI drive!

http://www.geocities.jp/kugimoto0715/rascsi/index.html

It now supports 256 byte sectors and so it may work with the Beeb as is, or else the developer may be willing to assist.
Last edited by IBM portable PC on Mon Mar 04, 2019 4:32 am, edited 1 time in total.
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Re: SCSI Progress At Last

Post by IBM portable PC » Mon Mar 04, 2019 4:39 am

Necroposting I know, however, for those of us who wish to continue to use our Acorn or Akter Adapter board and Adaptec controller, what are most now using as an actual drive?

Still a hard drive, or a Pi or some other SCSI drive emulator...
Last edited by IBM portable PC on Mon Mar 04, 2019 4:41 am, edited 1 time in total.
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