15 Jun
2011
15 Jun
'11
3:17 a.m.
Ok, progress on checking out this Sorcerer BASIC ROM-PAC..
I diescovered there was no way you could exit to the monitor program if you
had a hung ROM-PAC plugged in BUT....I figured out a way to check the
content of the ROM-PAC ROMS.
In the Sorcerer the ROM-PAC occupies space from C000-DFFF using 4 chips.
Reading the docs I saw that the boot up sequence jumps to DFFD or DFFA
depending on if it's a warm or cold start. However, if it finds nothing
there, it assumes there is no ROM PAC attached and boots up the monitor.
YES! This means all I needed to do is remove the number 4 IC (D800-DFFF)
and I should be able to boot to the monitor and then examine the contents of
the three lower ICs. I could then substitute the number 4 IC for one of the
lower ones and examine its contents too.
I removed the number 4 chip, plugged in the ROM-PAC and booted. Success, I
was in the monitor. I then dumped the memory locations corresponding to the
ROMS. The two lower ICs (C000-CFFF) showed all different hex numbers. In
other words it looked like it contained good code. However, the third IC
(D000-D777) contained all zeros!! I then swapped over the D800-DFFF chip
I'd removed into the socket which originally contained the D000-D777 and
checked that number 4 chip. The code looked good and I could even see the
bootstrap code at the end at DFFD and DFFA (of course it was at location
D7FD and D7FA as I had this number 4 chip in socket 3).
Conclusion. It's the number 3 IC which is faulty.
Next task. Unpack the EPROM burner and try to figure out how to use it.
Terry (Tez)
----- Original Message -----
From: "Terry Stewart" <terry at webweavers.co.nz>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
Sent: Wednesday, June 15, 2011 1:41 PM
Subject: Re: New rest-home resident: An Exidy Sorcerer
I don't
know if I can disable the autostart but then I haven't looked
through the manual yet. Hopefully I can by holding some keys down when
switching off (or something).
Or perhaps more useful, when switching ON! (sorry..typo)
Terry (Tez)
----- Original Message -----
From: "Terry Stewart" <terry at webweavers.co.nz>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
Sent: Wednesday, June 15, 2011 1:22 PM
Subject: Re: New rest-home resident: An Exidy Sorcerer
>> I must get mine set up again. From where I am sitting I can see the
>> fornt
>> side of the S100 expansion unit...
>
> Nice. I would love an expension unit for the Sorcerer but is was hard
> enough to actually find the computer itself here in New Zealand. I think
> it will have to remain one of those wistful thoughts.
>
> I've decided to have a crack at fixing this BASIC ROM-PAC over the next
> few months. This is probably a good opportunity to actually LEARN about
> burning EPROMS and I'm sure I'm going to need to do so if I want to keep
> my 70's and 80's computers going for the next 20 years.
>
> It's going to be a big learning curve for me as my knowledge is still
> fragmented in this area. Also it's likely to be a slow project as there
> are lots of competing activities at the moment. However, hopefully you
> guys can assist if I need to ask what (to you) might seem stupid
> newbie-type questions.
>
> Of course I'm only ASSUMING it's the ROMS. There is not much else in the
> case though apart from a few caps and a logic chip or two. Is there any
> quick technique to determine if it IS the ROMS and if so if any
> particular ROM is faulty?
>
> One way that comes to mine with the Sorcerer is to somehow prevent the
> ROM-PAC from autostarting, then peer into the memory locations the
> ROM-PAC occupies (with the inbuilt monitor) to see if any of the memory
> seems messed up (with repeating patterns etc.). If NONE of the memory
> locations appear accessible this would indicate it might be something
> OTHER than the ROMS yes? (as it's unlikely all 4 ROMS would have
> developed a fault). Is this a reasonable approach to start off?
>
I don't know if I can disable the autostart
but then I haven't looked
through the manual yet. Hopefully I can by holding some keys down when
switching off (or something).
>
> Anyway...I'll report any progress.
>
> Terry
>
>
>
-----
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Version: 10.0.1375 / Virus Database: 1513/3693 - Release Date: 06/10/11