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View Full Version : Xebec S100 SASI Host interface... Who has one? Any documentation? Any pictures?



Roland Huisman
June 22nd, 2017, 11:40 AM
It seems Xebec made an S100 sasi controller by themselves...
We were figuring out the software for the byte article and also there are errors...
Freek Heite mentioned the existence of original Xebec software for their S100 SASI interfase.

39222

According the documents the Xebec S100 controller was not able to boot.
The example schematics in the S1410 documentation just show a simple
host interface. I guess this should come very close to the Xebec S100 SASI board.
39221
I really would love to see a picture or documentation of that particular board.


At this moment I have the PCB's for the Byte HCA S100 SASI host controller in production.
http://www.vcfed.org/forum/showthread.php?57716-S100-hard-disk-controller&p=464059#post464059

This PCB from the Byte article is able to boot because there is an EPROM on it.
I Think I've recovered all errors from the Byte article. The unit from that article is
based on the Xebec example circuit. That was very useful to find errors...
The original Xebec software will probably help a lot too. Because the Byte article
contains many errors and isn't quite complete...

But I think it is very interesting to see the Xebec S100 host interface! Does anyone have it?
Is there any documentation? Any pictures?

Regards, Roland

Chuck(G)
June 22nd, 2017, 12:21 PM
SASI tends to be a very simple SCSI-1 interface, no?

Al Kossow
June 22nd, 2017, 12:52 PM
there is a seriously mangled ocr of the manual here

https://amaus.net/static/S100/software/rlee/S/SASI-SCSI/S100SCSI/


also, this is the same board that DTC sold as the DTC-10 (or DTC-10-1 with DMA)
DTC-10-1_S-100_SASI_DMA_Adapter_Preliminary_Specification_Apr 81.pdf on bitsavers has a schematic

I've got a board around somewhere I'll see if I can take a picture of it.
The same was true between DTC and Xebec for the Multibus host adapters.

Roland Huisman
June 23rd, 2017, 02:19 PM
Thanks! The D10-1 schematic is completely different from the Xebec example schematic.

Which one do you have? The DTS-10 or DTS-10-1? Very curious!

Regards, Roland

new_castle_j
October 15th, 2017, 08:46 AM
Roland,
I think I found an Xebec SASI controller for the S-100 in my collection. Up until now I did not know what it was, but reading this thread caused me to dig it out again and do some research. Here is a photo from the Xebec brochure on bitsavers (http://www.bitsavers.org/pdf/xebec/brochures/Xebec_Brochure_1984.pdf)

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and here is a photo of my board, which has no brand name on it at all, it's simply labeled S100 Host adapter:

41344

new_castle_j
October 15th, 2017, 01:21 PM
I found a copy of the manual for this board in Rlee Peters archive!! It was riddled with odd characters and goofy spacing (I think it was an OCR capture), but I have cleaned it up and it's now readable with MS Wordpad (other txt editors skew the text alignment, don't know why). Anyways, here it is.

41345

Roland Huisman
October 21st, 2017, 01:10 AM
Great! Thanks for the picture! That is more like what I expected. The PCB seems to
have some extra possibilities. Probably they used the same PCB for differed versions?

I really have to go further with my HCA project...
It has been waiting since other project came across...

http://www.vcfed.org/forum/showthread.php?57716-S100-hard-disk-controller&p=472344#post472344

new_castle_j
December 19th, 2017, 07:05 AM
Just making a follow up post here, yesterday I finally found success in making my Xebec s100 SASI card work! It was quite an adventure, but very satisfying to see it in action. This was a board that I previously did not know what it was for until Roland posted an inquiry here and the gears in my head started moving. This card was sold by Xebec and was meant to be paired with their s1410 SASI to MFM bridge board. In my case I did not have a s1410 to play with, so I acquired a SCSI2SD device shown here: https://store.inertialcomputing.com/SCSI2SD-p/scsi2sd-v5b.htm
A firmware update from the developer causes it to emulate the s1410 and data storage happens on a mini SD card. I had problems running the SASI card with an 8Mhz z80, but after switching to 6Mhz, everything is working! I'm curious if other SASI boards would require different code to run or if SASI implementations are mostly vanilla. Anyways, this forum helped make another success story!

Al Kossow
December 19th, 2017, 07:18 AM
if SASI implementations are mostly vanilla.

SASI (Xebec, DTC, SMS) and early SCSI (like the Adaptec 4000) bridge boards have differing command sets.

Some of the earliest ones required you to specify the drive's Head,Track when they were powered up, for example,
some stored the information on the front of the disk. SCSI eventually came up with a "Common Command Set"
that most of the embedded SCSI drives use, but those can return unique mode sense pages, the most common
difference is the drive type and geometry returned.

Chuck(G)
December 19th, 2017, 08:30 AM
One of the SMS controllers that I used (the RLL-to-SCSI one) didn't support much of the SCSI command set other than read, write and format. ISTR that the way you got the drive geometry was to read the sector buffer after boot.

Early SCSI was ? fun...

Terry Kennedy
December 21st, 2017, 02:38 PM
SASI (Xebec, DTC, SMS) and early SCSI (like the Adaptec 4000) bridge boards have differing command sets.

Some of the earliest ones required you to specify the drive's Head,Track when they were powered up, for example,
some stored the information on the front of the disk. SCSI eventually came up with a "Common Command Set"
that most of the embedded SCSI drives use, but those can return unique mode sense pages, the most common
difference is the drive type and geometry returned.
The non-DMA Xebec S-100 adapter was not exactly fast, even back in the day. I managed to get equivalent performance just doing bit-fiddling on some glorified parallel ports for some systems that didn't have S-100 slots. SASI was pretty simple - SCSI added synchronous mode, disconnect, and lots of other stuff that was harder to implement in code + ports only - some sort of state machine was always a better solution. When we sold systems that needed higher performance, we used Priam drives and the ADSI (ADES, back then, before the negative connotation of that pronunciation) S-100 host adapter.

BTW, the 1410 had a different EPROM on it for various drives. As I recall, the Syquest SQ306 used a piece of each track on the cartridge near the index for servo information (AKA servo wedge) and you would wipe that if you used the vanilla 1410 ROM and tried to format the cartridge.

cbscpe
January 7th, 2018, 12:01 PM
Just making a follow up post here, yesterday I finally found success in making my Xebec s100 SASI card work! It was quite an adventure, but very satisfying to see it in action. This was a board that I previously did not know what it was for until Roland posted an inquiry here and the gears in my head started moving. This card was sold by Xebec and was meant to be paired with their s1410 SASI to MFM bridge board. In my case I did not have a s1410 to play with, so I acquired a SCSI2SD device shown here: https://store.inertialcomputing.com/SCSI2SD-p/scsi2sd-v5b.htm
A firmware update from the developer causes it to emulate the s1410 and data storage happens on a mini SD card. I had problems running the SASI card with an 8Mhz z80, but after switching to 6Mhz, everything is working! I'm curious if other SASI boards would require different code to run or if SASI implementations are mostly vanilla. Anyways, this forum helped make another success story!
I also happen to have a controller on my PDP-11 that interfaced with a Xebec s1410. What firmware and what settings did you use on the SCSI2SD to emulate the S1410?

new_castle_j
January 9th, 2018, 09:09 AM
I also happen to have a controller on my PDP-11 that interfaced with a Xebec s1410. What firmware and what settings did you use on the SCSI2SD to emulate the S1410?

I worked directly with the developer and received the firmware update from him, it's not been posted for download yet. PM me if you want it, it is for the v5 scsi2sd device.

cbscpe
January 11th, 2018, 05:35 AM
Sent him a mail as well and got the Firmware. He plans to bring that to the official release, as soon he finds time :p. I'll give it a try this Weekend. The tricky thing will be probably that the SCSI2SD will report back something useful for the Plessey RL02 Controller when he does power-on selftest.

Roland Huisman
January 14th, 2018, 10:32 PM
Very nice, but I thought the US is full of the original Xebec 1410 controllers?

I really would like to experiment with those SASI 2 SD controllers as well...