20 Dec
2013
20 Dec
'13
8:58 a.m.
Does anyone know exactly what was in the Lobo branded "SASI" external
hard
drive? I've managed to convince my Max-80 to talk
with a 10MB MFM drive
behind an Adaptec ACB-4000 bridge controller. It
formats and verifies
without a complaint, accepts bad sector information and creates a working
CP/M volume. But, for some reason I cannot get it to
boot from the hard
disk.
It won't be the end of the world if I have to cold-start from a floppy,
but my curiousity is getting the better of me. The utility that writes
the boot sectors works fine - there's a brief flicker of drive activity
and no error messages. When I set the DIP switches to cold-boot the hard
disk, I can see the busy LED on the bridge board light
up solid and the
machine freezes. Under normal I/O, the drive activity LED illuminates at
the same time as the one on the ACB-4000, but at boot
I never see the
drive itself respond.
I'm assuming that there's some incompatibility between the ACB-4000 and
the boot PROM. It would help to know what it's expecting to see. I've
been digging through the boot ROM sources, but nothing jumps out so far.
FWIW, I've tried an Adaptec ACB-5500 controller (same results), a Xebec
1410 (won't format or verify, but can be written/read) and a Xebec 1410A
(I/O errors).
Steve
Steve,
What OS are you using? I understand that the original OS had an OS bug
related to direct hard drive booting. I can check around if you have not
yet resolved the problem
Bill
20 Dec
20 Dec
4:12 p.m.
On Fri, 20 Dec 2013, B. Degnan wrote:
> I'm assuming that there's some
incompatibility between the ACB-4000 and
> the boot PROM. It would help to know what it's expecting to see. I've
> been digging through the boot ROM sources, but nothing jumps out so far.
Steve,
What OS are you using? I understand that the original
OS had an OS bug
related to direct hard drive booting. I can check around if you have not
yet resolved the problem
Hi, Bill.
I think you are close. Yesterday I discovered their 'boot.com' utility.
It is intended to cold-boot the machine from any arbitrary attached device
regardless of DIP switch setting. In looking at the source code, I
discovered that it can also read an arbitrary file from disk and use that
instead of the boot PROM on the system board. When I told it to use the
'maxrom13.com' image on the CP/M distribution diskette, lo and behold it
booted the hard drive!
I popped open the unit and sure enough the PROM was labeled "Lobo 1.2".
So it looks like the fix went in with version 1.3 and I'll need to blow a
new PROM.
Unfortunately, when reassembling the unit I managed to get the ribbon
cable between upper and lower PCBs off by one pin and smoked several chips
on the keyboard portion :-(. It took out the LS240 that reads the
keyboard matrix and both LS05s that provide the matrix scan from the
address bus. I'm about half way to having it up again. Good to keep
one's bench skills sharp...
In order to blow an LS472 PROM, I need to build the appropriate jumper
headers for my programmer - a job in itself. But I'm reasonably sure that
will get it starting from the hard drive.
FYI: The Adaptec ACB-5500 seems to be the most compatible SASI controller.
Steve
--
22 Dec
22 Dec
2:52 p.m.
On Fri, 20 Dec 2013, Steven Hirsch wrote:
On Fri, 20 Dec 2013, B. Degnan wrote:
What OS are
you using? I understand that the original OS had an OS bug
related to direct hard drive booting. I can check around if you have not
yet resolved the problem
I think you are close. Yesterday I discovered their
'boot.com' utility. It
is intended to cold-boot the machine from any arbitrary attached device
regardless of DIP switch setting. In looking at the source code, I
discovered that it can also read an arbitrary file from disk and use that
instead of the boot PROM on the system board. When I told it to use the
'maxrom13.com' image on the CP/M distribution diskette, lo and behold it
booted the hard drive!
I popped open the unit and sure enough the PROM was labeled "Lobo 1.2". So it
looks like the fix went in with version 1.3 and I'll need to blow a new PROM.
After correcting my self-induced hardware problem in the keyboard decoder,
I programmed the 1.3 firmware image into a 74LS472 PROM and gave that a
try. Now it boots from the hard drive with no issues. Life is good!
If any MAX-80 owners need the 1.3 PROM, get in touch with me via e-mail.
Now that I have the personality module built for 512x8 20-pin PROMs it's
simple to program more.
Steve
--
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billdeg＠degnanco.com -
snhirsch＠gmail.com