SCSI Progress At Last

discuss both original and modern hardware for the bbc micro/electron
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BeebMaster
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SCSI Progress At Last

Post by BeebMaster » Fri Jul 30, 2010 3:43 pm

As some of you many know, it's part of my life's mission to find some SCSI discs which will work when connected to a BBC host adapter, apart from the ones which are known to work (Seagate ST157N, Syquest SQ555 cartridge and one or two others).

I've been at it on and off for about 8 years but at last I seem to be getting somewhere. I've successfully persuaded a Seagate 2GB drive to respond to the Enquiry command, which is the first peep I've ever got out of anything "modern". I also got an old Maxtor drive to give me a disc error after *MOUNT and shut itself down with *BYE which is real progress, although sadly the disc is dying and currently won't spin up.

I think I've succeeded this time because I've made sure that the SCSI bus is terminated. In the past I probably haven't paid too much attention to this. I'm also using a ribbon cable with pin 34 cut because this provides 5V in the Acorn host adapter implementation whereas it should be connected to ground in the single-ended SCSI pinouts. That's been the cause of many a BeebMaster fire over the years, including the Great FileStore Fire of 2003!

The question associated with this ramble is, now that I can get some drives to respond to an Enquiry command, why can't I get them to do anything else? If I send any other type of command to them (Mode sense, mode select, read sectors, etc) then the machine locks up till I press BREAK, and if I try to mount one of these discs there is no response.

Tantalisingly, the light on the Seagate one twinkles when I try *MOUNT but nothing ever happens!!

Surely I should get some sort of disc error if I try to mount a disc which ADFS doesn't like? And why is the machine locking up (presumably never returning from the OSWORD call) if I send anything apart from Enquiry?

I'm wondering if there is any way to talk to the host adapter directly without going through the ADFS osword call, but I reckon that's probably going to be messy.
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Re: SCSI Progress At Last

Post by station240 » Fri Jul 30, 2010 4:35 pm

I tried to reconfigure a couple of SCSI drives to use 256 byte sectors, didn't works as its blocked in the drive's firmware. I could make 1024 byte sectors though. I'm wondering if tamper with the hard drive's own ROM could be a solution.

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Re: SCSI Progress At Last

Post by BeebMaster » Fri Jul 30, 2010 8:40 pm

I've always thought (possibly no more than mindless sunny optimism) that the 256-bytes-per-sector lark was a bit of a red herring. I know that if I can't persuade a drive to work with 256-byte sectors then I can't expect Superform to do the business for me and some serious hackery is probably needed. But having said that, surely when you've got a drive attached which is responding sensibly to the enquiry command, an attempt to mount it should result in some disc activity and eventually a disc error. I can't understand why I'm not able to get to this stage.

The disc currently attached to the host adapter is a Seagate ST52160N and it's given name, rank & serial number in response to Enquiry but it won't do anything else. I know it's formatted to 512-bytes-per-sector because this is the drive I use with the SCSI podule on my A5000, so the fact that it isn't 256 bps doesn't of necessity mean that the drive is ignored.

I've got quite a few SCSI discs of varying vintages and some of them do support 256 bps when you read into the spec a bit more, even though they are usually listed as 512, but the trouble is I can't seem to send a mode select command to them to put them in 256 byte mode.
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Re: SCSI Progress At Last

Post by sirmorris » Sat Jul 31, 2010 8:51 am

Just having a Saturday morning muse but:

'I'm also using a ribbon cable with pin 34 cut because this provides 5V in the Acorn host adapter implementation whereas it should be connected to ground in the single-ended SCSI pinouts. '

Is the cut end also grounded? Because if not then more likely than not it's 'floating' and that could cause problems for you.

I might redact this after having another coffee :)

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Re: SCSI Progress At Last

Post by BeebMaster » Thu Aug 05, 2010 6:24 pm

sirmorris wrote:Just having a Saturday morning muse but:

'I'm also using a ribbon cable with pin 34 cut because this provides 5V in the Acorn host adapter implementation whereas it should be connected to ground in the single-ended SCSI pinouts. '

Is the cut end also grounded? Because if not then more likely than not it's 'floating' and that could cause problems for you.

I might redact this after having another coffee :)
Naah, I just cut the wire on the ribbon cable, didn't attach either end to anything new. What should I have done?
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Re: SCSI Progress At Last

Post by sirmorris » Fri Aug 06, 2010 12:18 pm

The SCSI end should be grounded. At the moment it's 'floating' and may provide spurious signals to the controller which would at best lead to intermittent problems.

You'll need to attach the wire to another ground wire. Is it a 50 way ribbon? In which case pin1 & pin 50 are both gnd.

C

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Re: SCSI Progress At Last

Post by BeebMaster » Tue Aug 16, 2011 12:48 am

Well, it's been a year since I posted anything here but I am now able to announce...

I'VE DONE IT AT LAST AFTER 9 YEARS!


So here's how to make a modernish SCSI disc work with a very oldish BBC, in 20 easy steps!

All you need is a BBC Micro, dual disc drive, a few SCSI discs, host adapter board, BBC PSU to power the host adapter, some jumpers, terminating resistors, bit off an Atari, screwdriver, pens, paper, SCSI manuals, TV, DVD recorder, SVHS VCR, and some tea & cakes:
SCSISuccess1.jpg
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A 512MB drive, working under ADFS:
SCSISuccess3.jpg
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Responding quite happily to the Enquiry command:
SCSISuccess5.jpg
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Here's the Operating Definition Enquiry page, this is critical as the drive must be set to Operating Definition 1 (SCSI-1) to work with a BBC:
SCSISuccess7.jpg
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Verified OK!
SCSISuccess10.jpg
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Next add an A5000 with SCSI podule:
SCSISuccess11.jpg
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The Beeb won't talk to anything more modern than a SCSI-1 drive, so we have to use the Archimedes to issue a Change Definition command:
SCSISuccess17.jpg
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Termination and Parity settings are crucial to get the drive working with a Beeb:
SCSISuccess35.jpg
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Parity checking disabled (link open) and terminator enabled and powered (links closed):
SCSISuccess37.jpg
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The same drive back with the Beeb, and now reporting itself as a SCSI-1 device:
SCSISuccess45.jpg
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Re: SCSI Progress At Last

Post by BeebMaster » Tue Aug 16, 2011 1:03 am

The drive responds to a mode sense command, but it's still set to 512 bytes per sector. ADFS requires 256-byte sectors:
SCSISuccess49.jpg
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Read capacity shows we're dealing with a 1GB drive:
SCSISuccess51.jpg
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The next step is to format the drive to 256-byte sectors:
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Takes about 35 minutes but it goes through OK:
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Mode Sense 3 tells us the format parameters, and now it's 256 bytes per sector:
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Mode Sense 4 tells us about the disc geometry, Read Capacity appears to have come up with a slightly random number of blocks but it's still more than we need:
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Verification completion:
SCSISuccess65.jpg
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Now we need to write a free space map and root directory:
SCSISuccess66.jpg
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ADFS uses 21-bit disc addresses, so the maximum number of sectors we can use is 2 million, giving 512MB of space:
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I like to title my discs with information about the model & size:
SCSISuccess85.jpg
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I've got to thank RobC for the information about the Change Definition command, that really is the nub of the whole thing I think, and I couldn't have worked that out for myself!

I'm off now for an enormous celebratory cup of tea; I feel kind of relieved that they can now put on my grave stone "He formatted a 1GB SCSI Disc Using a BBC Micro".
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Re: SCSI Progress At Last

Post by AndyF » Tue Aug 16, 2011 11:26 am

Congrats :)
Andy

* NEW * The Jetset Willy and Manic Miner community :)

Adventure games ported across to the BBC (in progress) as soon as I can find some time!

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Re: SCSI Progress At Last

Post by BeebMaster » Tue Aug 16, 2011 6:32 pm

Thanks, it's been a labour of love for a long time, and could have all come together at just about the right moment - the old Rodime in my Acorn Winchester Disc 130 is taking about 10 mins to spin up to speed, so I might need an alternative soon!

I've formatted 4 Seagate drives now, but I'd run out of jumpers by the fourth one. These drives take tiny little ones much smaller and flatter than used in a Beeb. Luckily I had a bit of tinfoil handy:
SCSISuccess86.jpg
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Re: SCSI Progress At Last

Post by george.h » Tue Aug 16, 2011 9:57 pm

Superb bit of work! =D>

I think I'll have to get my 1GB Seagate SCSI drive out again. Last time I played with it (using an old Ahkter host adaptor) I got as far as finding and using the low-level SCSI format command to reformat the drive using 256 byte sectors from the original 512 byte sectors. The drive came out of an old Netware 3.12 server years ago. If memory serves my major stumbling point after that was trying to modify one of several WForm utilities to work - without success at the time :lol:

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Re: SCSI Progress At Last

Post by BeebMaster » Wed Aug 17, 2011 12:37 am

I think you'll be fine with a Seagate one, they tend to support the Change Definition command and sector sizes as low as 180 bytes. Seagate also publish the manuals online, if you put "Seagate" followed by the exact model number into Google then a link to a PDF of the manual will almost certainly come up, which will give all the supported commands and the jumper settings.

If you managed to do a format of the disc previously then you're probably very nearly there. The only step after that should be to write the ADFS map & root, and you can adapt "Superform" to do that.

The Winchester formatters floating around probably aren't quite the ticket because many of them are based on ST506 controllers so they probably do the mode select part incorrectly. There's also usually a lot of code in them for dealing with defects, which shouldn't be necessary nowadays as drives are shipped defect-free, unlike in the 1980s when they were sold already part knackered for some reason!

Also, there's no need to get bogged down in trying to understand all the cylinders, heads and sectors per track business. That used to be important with ST506 drives because the controller was separate, so it didn't know what disc geometry it was dealing with, and you had to tell it what to expect. As long as you set the disc to 256 byte sectors and start it formatting, the drive will do the rest.

For reference for anyone starting from scratch, there are essentially 6 steps to getting going:

1. Make sure the jumper settings are correct. Set the SCSI ID to 0 (it should be possible for ID 1 to be supported as well, and possibly also 2 & 3 under ADFS, but I haven't looked into that much as yet.) Parity checking must be disabled and any on-board terminators need to be enabled and powered.

2. Cut pin 34 of the 50-way ribbon cable otherwise it will melt, and add an active SCSI terminator to the end of the cable.

3. Send an Enquiry command to the drive from the BBC. If it's set up and jumpered and terminated correctly (even if it's not set as a SCSI-1 device) you should get a response of the model & serial number etc.

4. Send a change definition to the drive to change it to definition 1. Unfortunately this can't be done on a BBC, as anything apart from an Enquiry command won't get through to a SCSI-2 or SCSI-3 device. This has to be done on an Archimedes (or PC) with SCSI interface. If the definition is forgotten by the drive after being powered down, then also do a Format Unit command immediately after the Change Definition.

5. Connect the drive back to the Beeb and issue a Mode Select command with a block size of 256 bytes per sector, then a Format Unit command without a defect list or any other format parameters. This will take about half an hour or so for a 1GB drive, longer for anything bigger. The BBC will appear to lock up whilst this is happening but this is normal and it will come back when the format is finished.

6. Write the first 7 sectors to the disc, being the free space map and root directory. The maximum number of sectors you can get under ADFS is &200000, any more than this gives a Bad FS map error as the top 3 bits of the disc address are reserved for the drive number.

Eventually I'll put together a disc of utilities to do everything that's required, I'd like to see more SCSI discs being used with Beebs! Perhaps then we can show that real, spinning, whirring, clunking mechanical drives are the thing to use and that all this new-fangled gubbins is just a flash card in the pan!
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Re: SCSI Progress At Last

Post by paulv » Wed Aug 17, 2011 1:21 am

Hmmm... I have a small stack of 1 and 2GB Seagate Barracudas from an old Compaq ProSignia server that may just come in handy after all :D

Paul

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Re: SCSI Progress At Last

Post by station240 » Wed Aug 17, 2011 2:24 am

The only SCSI drives I have are from old Apple Macs, and those definitely do not support 256 byte sectors, I tried it.

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Re: SCSI Progress At Last

Post by paulv » Wed Aug 17, 2011 7:48 am

I've just checked the manual and as Ian said, my Barracudas have selectable sector sizes from 180 to 4096 bytes per sector...

Now all I need is the terminators, cables and a SCSI card for the Master :D... I've not tried the Cumana SCSI card in my Arc yet but I should be set hardware wise to be able to follow in Ian's wake :D

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Re: SCSI Progress At Last

Post by george.h » Wed Aug 17, 2011 10:14 am

Thanks for the tips BeebMaster. My drive is a ST31230N and have the full SCSI manual for it. Must admit I'd missed the Change Definition command. I do remember that I did find that the drive would not respond to anything until I'd sent and Init command (or was it an Enquiry, can't remember it was quite a while ago).

Heheheh - I know what your mean about pin 34 (bus termination power IIRC). I cut the track on my Akhter host adaptor very early on when I found it shorted the power out on my Beeb!

I think I did manage to get it formatted in ADFS but had issues with the free space map, and particularly the limit on the max number of sectors under ADFS. Just need to modify my external SCSI drive cased to take the Akhter board as well as the drive and replace the SCSI-1 connectors on the back with 1MHz bus connectors.

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Re: SCSI Progress At Last

Post by BeebMaster » Wed Aug 17, 2011 3:37 pm

station240 wrote:The only SCSI drives I have are from old Apple Macs, and those definitely do not support 256 byte sectors, I tried it.
If they'll do a Change Definition command, you might get away with it - as long as somebody can do a patch for ADFS similar to the IDE version to throw away the first 256 bytes of every 512-byte sector which ADFS receives!
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Re: SCSI Progress At Last

Post by BeebMaster » Wed Aug 17, 2011 3:46 pm

paulv wrote:I've just checked the manual and as Ian said, my Barracudas have selectable sector sizes from 180 to 4096 bytes per sector...

Now all I need is the terminators, cables and a SCSI card for the Master :D... I've not tried the Cumana SCSI card in my Arc yet but I should be set hardware wise to be able to follow in Ian's wake :D
Sounds promising! This Change Definition thing is the key - I've just been trying a Seagate ST52160N with no luck, but that's because it's a SCSI-3 device and doesn't support Change Definition. Also it doesn't support anything other than 512 byte sectors, so it's not going work.

Probably it's a good job, I mounted it in the A5000 and it turned out to be the disc I'd put all my Domesday rescue data on in 2006!

There are instructions on how to build a host adapter in the Hard Drives documentation at BBC Docs here:

http://www.bbcdocs.com/filebase/library ... e-v1.2.zip

That's the only bit of hardware required apart from the disc drive, all the references to Winchester controllers aren't necessary with SCSI discs.
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Re: SCSI Progress At Last

Post by BeebMaster » Wed Aug 17, 2011 4:06 pm

george.h wrote: Heheheh - I know what your mean about pin 34 (bus termination power IIRC). I cut the track on my Akhter host adaptor very early on when I found it shorted the power out on my Beeb!
Thank God for that, I thought it was just me that had this problem!
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Re: SCSI Progress At Last

Post by BeebMaster » Mon Aug 22, 2011 3:17 pm

Well, from the empirical evidence I've gathered, it looks like it could well be that the Seagate manufactured drives are unique in being able to work with the BBC host adapter arrangement.

So far they are the only drives which support the Change Definition command, and the only SCSI-2 drives which support a sector size as small as 256 bytes.

I've drawn a blank with IBM, Compaq, Quantum and various other makes.

Even more curious is that none of my SCSI-1 drives work either, even when I've been able to change the sector size to 256 on the A5000. All these drives just cause the Beeb to lock up, apparently never returning from the OSWORD call.

I've got a couple of Fujitsu drives which have a switch or jumpers to select between SCSI-1 or SCSI-2 but they still don't work. Even my Mad Miniscribe 8425S (exactly the same as the MFM 8425 which was used in some early Arcs except that it's SCSI) doesn't work!

Maybe I've missed a step here in my ANSI Standards definition history - is SCSI-1 the same as SCSI? Or did it go SCSI, SCSI-1, SCSI-2, SCSI-3 etc?
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Re: SCSI Progress At Last

Post by TopBanana » Mon Aug 22, 2011 3:33 pm

Totally OT - I've just read BeebMasters location.

Location: As close as possible to a fire engine.

ROFL :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: =D> =D> =D>

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Re: SCSI Progress At Last

Post by george.h » Mon Aug 22, 2011 6:31 pm

You could try sending a Unit Attn (IIRC)......
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Re: SCSI Progress At Last

Post by station240 » Mon Aug 22, 2011 6:42 pm

BeebMaster wrote:Well, from the empirical evidence I've gathered, it looks like it could well be that the Seagate manufactured drives are unique in being able to work with the BBC host adapter arrangement.

So far they are the only drives which support the Change Definition command, and the only SCSI-2 drives which support a sector size as small as 256 bytes.

I've drawn a blank with IBM, Compaq, Quantum and various other makes.
Figures, Apple used Quantum SCSI drives, so while there are tons of them around, they are useless for this task. :(

I got given a ISA slot SCSI card from an old IBM machine, but its minus the drive as its ex government and they trash the drives. :x

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Re: SCSI Progress At Last

Post by BeebMaster » Wed Aug 24, 2011 3:26 pm

I've ended this SCSI session for now, and I think I can be pretty pleased with the way things turned out. I did have a final go with the Syquest EZ135 drive which started it all off, but despite accepting a Mode Select command to set it to 256 byte sectors, it was in fact fibbing and didn't do anything of the kind. That's a bit of a shame, as its predecessor the SQ555 does support 256 byte sectors. So far, although I've formatted a cartridge and written an ADFS map and root, it doesn't work reliably under ADFS, sometimes giving Broken directory or Bad FS map errors, and sometimes mounting and appearing to work but giving Bad sum.

The one thing I haven't been able to do yet, which will be a job for the next SCSI session, is to get drives recognised when they are set to drive 1 (and possibly 2 or 3). Setting the ID of a SCSI drive to anything other than 0 doesn't appear to work. I think that may be something to do with the difference between the SCSI controller ID and the Logical Unit Number, but it will need a bit more investigation next time round.
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Re: SCSI Progress At Last

Post by IanB » Sun Sep 04, 2011 10:58 pm

Somewhere I've got a small program which patches ADFS to use different SCSI IDs for different drive numbers. Let me know if you want a copy and I'll try and find it.
I think I also have a version of ADFS that's been patched to handle 512 byte sectors.

IanB

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Re: SCSI Progress At Last

Post by BeebMaster » Mon Sep 05, 2011 7:44 pm

All that would be good, I did have a look at JGH's IDEPatch a week or two ago to see if I could extricate the bits which do the 512-byte sector processing from the bits which do the IDE talking instead of SCSI. Needless to say, I couldn't!
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Re: SCSI Progress At Last

Post by IanB » Mon Sep 05, 2011 9:57 pm

Here's the SCSI drive number patcher for the Master128 ADFS. It also changes a few other things and reduces some error messages to free up space.
There are two patch options:
1 - maps drives 0-3 to SCSI IDs 0-3
2 - maps drives 0&1 to SCSI ID 0 and 2&3 to SCSI ID 1 (This was so you could attach two ADAPTEC ST506 controller cards)

Although I wrote the patch, I can't remember much about it as it was 23 years ago!, so use with care and don't connect up drives with any valuable data until you are sure it works properly.

I'm still looking for the 512 byte sector patcher but one thing I should add is that it used the full 512 bytes from each sector and required a support ROM with the extra code so maybe that would be of use with some of the IDE interfaces.

IanB
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Re: SCSI Progress At Last

Post by retroclinic » Tue Sep 06, 2011 3:11 pm

IanB wrote:I'm still looking for the 512 byte sector patcher but one thing I should add is that it used the full 512 bytes from each sector and required a support ROM with the extra code so maybe that would be of use with some of the IDE interfaces.
That would be really useful. Most of the separate IDE interfaces are 8 bit only, so wouldn't be suitable. There's an IDE only card by Sprow which does 16 bit, but all my DataCentre boards have a 16 bit interface as standard, of which we currently only use 8, so it would be good to get it working with those.

Mark.
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Re: SCSI Progress At Last

Post by BeebMaster » Tue Sep 06, 2011 7:41 pm

I've put the full result of my recent SCSI session here if anybody wants more detail, there are nearly 200 pictures in 6 sets:

http://www.beebmaster.co.uk/UsingSCSI.html
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Re: SCSI Progress At Last

Post by julians » Sat Oct 01, 2011 5:38 pm

I'm impresssed. And jealous. And now I want to do the same with something similar from my junk pile of SCSI stuff.

I can't imagine they'd be that common, but does anyone have a stash of SCSI cards available for sale or can they be built relatively easily? Doesn't look like much is on the card itself.
There were a few messages a while back about a 'Possible run of SCSI boards for Master AIV wannabe' would this work with ADFS or does it just support controling the laserdisc player?

Julian.

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