[sci.electronics] SASI chips

p_e@obelix.liu.se (P{r Emanuelsson) (01/12/88)

I have a couple of CDC BR3B5 disks I want to talk SASI to. I'm going
to whip up something simple, but I want your advice on which controller
chip I should go for. The discs complicate the matter by having
19 heads and a bit rate of 6.5 MHz. They want MFM coded data.

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Dept of Comp and Info Science	(uunet!mcvax!enea!liuida!obelix!p_e)
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p_e@obelix.liu.se (P{r Emanuelsson) (01/19/88)

I wrote:
>I have a couple of CDC BR3B5 disks I want to talk SASI to. 
>[...]
>which controller chip I should go for?
>The discs complicate the matter by having
>19 heads and a bit rate of 6.5 MHz. They want MFM coded data.

Maybe I was a bit unspecific since I only got one reply (hi Doug! --
uunet doesn't like ames@uucp so no reply from me).

Well, the disks don't have a controller but I have full documentation.
They're not SMD, but maybe some predecessor. Anyway, I only have
Western Digital's Databook and cannot find a suitable controller.
WD1010 or 2010 are out, it would be too much problem interfacing them.
(The disks don't want no "stepping pulse" for one. They want the
cylinder address on a control bus. And the bit rate is too high.)

Maybe the WD1050 SMD-controller would work. Of course, it wants a
bit rate of 9.677 Mbits/sec and uses NRZ coded data, not MFM.
There may be more differences. I don't know how serious they are.
I can't seem to find any reference on the feasibility of converting
NRZ <=> MFM right now, would it be easy?
At least it's got a control bus for communication with the disk.

Then I've got to have a host interface. I have no possibility of
writing a new device driver, alas, so I must use what's available.
What's available is SASI. :-(

I would much rather like SCSI, maybe I can build a dedicated
processor to take SASI packets, converting and feeding them to
an SCSI bus controller? Seems a bit overkill though...

Anyway, please answer the following:

1. Do you know of any disk controller chip meeting the following specs:
   - MFM coded data.
   - Able to talk to the disk on a "control bus" or whatever (cyl #, etc).
   - Handles at least 19 heads.
   - The usual stuff (formatting, error checking, etc...)
   Even "I think AMD has one..." may be useful, but please elaborate.

2. Where can I get an SASI bus controller chip?
   Does it exist?

3. Which SCSI bus controller chip would you recommend?

-- 
"Don't think; let the machine do it for you!"
                                   -- E. C. Berkeley
Dept of Comp and Info Science	(uunet!mcvax!enea!liuida!obelix!p_e)
Univ of Linkoping, Sweden	(p_e@obelix.liu.se, p_e@obelix.UUCP)

dbraun@cadev4.intel.com (Doug Braun ~) (01/20/88)

In article <1405@obelix.liu.se> p_e@obelix.liu.se (P{r Emanuelsson) writes:
>I wrote:

>2. Where can I get an SASI bus controller chip?
>   Does it exist?
>
>3. Which SCSI bus controller chip would you recommend?
>

I think SASI and SCSI are virtually identical for most purposes.
SCSI basically adds fancy things like syncronous transfer, arbitration,
more commands, etc., that you probably will not need.

I built a SCSI host interface for a custom Z80 system out of
latches and gates; it only took about 10 chips or so.

If your stuff is supposed to be connected to a PC,
a local surplus place has lots of host adapters for $15.
These were made by Ampex for a hard disk add-on system.
They have no documentation, but I have disassembled
the ROM code on them and written a device driver to
control a hard disk on my PC.

Halted Specialties in Sunnyvale (Call 408 555-1212 for the phone)
has the host adapters.  If anyone out there has bought one
or could use such a thing, let me know and I will post the code
for my device driver.

Doug Braun				Intel Corp CAD
					408 496-5939

 / decwrl \
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phil@amdcad.AMD.COM (Phil Ngai) (01/21/88)

In article <1578@mipos3.intel.com> dbraun@cadev4.UUCP (Doug Braun ~) writes:
>In article <1405@obelix.liu.se> p_e@obelix.liu.se (P{r Emanuelsson) writes:
>>I wrote:
>
>>2. Where can I get an SASI bus controller chip?
>>   Does it exist?
>>
>>3. Which SCSI bus controller chip would you recommend?

I am told that a simplistic SCSI controller is basically a parallel
port with 48 mA drive. This would include the NCR 5380. Western
Digital has a chip which implements much more of the protocol. I think
it's the 33C93.  (but don't take my word on these numbers. call a
salesman.)

I am of course biased because we second source both these chips.
But better to get some biased info than none at all, right?

-- 
The VT220 keyboard sucks, but the VT320 is usable. 
DEC finally got it right!

Phil Ngai, {ucbvax,decwrl,allegra}!amdcad!phil or phil@amd.com