[Coco] Color BASIC 1.1 / memory detection

Fri Feb 20 13:55:53 EST 2015

In article 
<CA+LuDcfMz7AEv99aXXeDi_2c=_hQbcJ_z2CqQv08j=wNAFWqGA at mail.gmail.com>, 
Arthur Flexser <flexser at fiu.edu> writes
>You mean $FF22, not $FF20, right?  (I suppose a bad bit in your Color 
>Basic
>ROM is considerably less likely than a typo, though it would explain 
>the
>problem.)

>Art

Yes, it's $FF22. Operator incompetence there and on more than one level 
because that bit of info made me look a lot closer around the PIA in 
question and spotted a jumper (well lack of actually) labelled 64K. 
Connect that up and it's coming back with the expected 32K.

Many thanks for your assistance.

Jon.

>On Thu, Feb 19, 2015 at 5:23 PM, jon bird <news at onastick.clara.co.uk> 
>wrote:

>> I've also just had a look through the Color Basic Unravelled document 
>to
> try and figure out how the ram size logic works. It seems there are 2 
bits
> coming into play from the PIAs:
>
> $FF02, bit #6 "RAM Strobe" (shared with a keyboard column line)
> $FF20, bit #2 "RAM Input"
>
> What seems to happen is that RAM Strobe is driven high, then RAM Input 
is
> checked and if zero, the 4K RAM map is selected. Assuming not, RAM 
Strobe
> is then driven low and RAM Input checked again. If zero, the 64K map 
is
> selected and if one, the 16K map is selected. So my guess is that it's 
this
> that is causing the problem.
>
> However I can't find any schematics online to show what this Ram 
Strobe
> line actually does. The only ones I can find are from the CoCo 
Technical
> Reference Manual which don't show this strobe line (presumably a 
latter
> feature). Does anyone have anything on this?
>
> Rgs,
>
> Jon.
>
> In article <CA+LuDccV4+Unb8TO-frQ5sfv01QSxWpsCLOyduobczhQr96
> stQ at mail.gmail.com>, Arthur Flexser <flexser at fiu.edu> writes
>
>> All I can think of is double checking that the jumpers are correctly 
set.
>>
>> Maybe also swap the positions of the RAM chips with one another to 
see if
>> that makes any difference (grasping at straws).  In the process, 
check to
>> make sure none of the RAMs have any bent-under pins.  I would think a 
bad
>> or inoperative RAM would keep the CoCo from booting at all, but who 
knows?
>>
>
>  Art
>>
>
> On Wed, Feb 18, 2015 at 12:41 PM, jon bird <news at onastick.clara.co.uk>
> wrote:
>
>
>>
>>
>>
>> It's definately a 1.1 ROM, the number is stamped on the chip and to 
be
>> sure I pulled the Extended ROM and confirmed it comes up with 1.1.
>>
>> I also did a quick sense check - POKEing some values above the 16K
>> threshold and they all appeared "stuck" at 255. Which suggests that
>>
> the
>
>> SAM has been programmed up for a 16K memory fit.
>>
>> Rgs,
>>
>> Jon.
>>
>> >
>> > Art, I have an F-board (chicklet keys) that has both CB & ECB 1.0.
>>
> It was
>
>> > one of the 32k boards that was actually 64k. Oddly, it recognizes 
as
>>
> 32k
>
>> > of ram and not as 16k.
>> >
>> >
>> > Bill Pierce
>> > "Today is a good day... I woke up" - Ritchie Havens
>> >
>> >
>> > My Music from the Tandy/Radio Shack Color Computer 2 & 3
>> > https://sites.google.com/site/dabarnstudio/
>> > Co-Contributor, Co-Editor for CocoPedia
>> > http://www.cocopedia.com/wiki/index.php/Main_Page
>> > E-Mail: ooogalapasooo at aol.com
>> >
>> >
>> >
>> >
>> > -----Original Message-----
>> > From: Arthur Flexser <flexser at fiu.edu>
>> > To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
>> > Sent: Tue, Feb 17, 2015 6:49 pm
>> > Subject: Re: [Coco] Color BASIC 1.1 / memory detection
>> >
>> >
>> > Are you sure that your COLOR BASIC (not Extended Basic) is version
>>
> 1.1?
>
>> > You cannot readily detect the Color Basic version with Extended
>>
> Basic
>
>> > installed.  If in doubt, pull the Extended Basic chip and see what
>>
> the
>
>> > startup message reports.  (Though I would think an F-board CoCo
>>
> would
>
>> > indeed have Color Basic 1.1, not 1.0.)
>> >
>> > Art
>> >
>> > On Tue, Feb 17, 2015 at 5:14 PM, jon bird
>>
> <news at onastick.clara.co.uk>
>
>> > wrote:
>> >
>> >> Hi,
>> >>
>> >> I have just recently resurrected my old Coco 1 (it's a 26-3004A
>>
> variant)
>
>> >> and have been putting it back to an original (working) state (I 
had
>>
> been
>
>> >> plugging various additional cards & even a Dragon ROM into it at
>>
> some
>
>> >> point).
>> >>
>> >> The info I can find on this version of the CoCo was that it was
>>
> shipped
>
>> >> with 16K RAM, Color BASIC. It had an Extended BASIC 1.1 ROM fitted
>>
> many
>
>> >> years ago and as part of my various "upgrades", replaced the 16K
>>
> RAM
>
>> >> chips
>> >> with 4164 DRAMs & also switched over the jumpers.
>> >>
>> >> What I am finding though is that having restored the original 
Color
>> >> BASIC
>> >> 1.1 ROM, it is only reporting a 16K memory fit. I'm pretty sure
>>
> that
>
>> >> when I
>> >> had the Dragon ROM fitted, it could access the full 32K (and I'm
>>
> also
>
>> >> fairly sure I had OS9 running on it as well which suggests the 
full
>>
> 64K
>
>> >> is
>> >> accessible). So this seems to be a feature of the BASIC ROM.
>> >>
>> >> I did come across this article from the archive:
>> >>
>> >>
>>
>>  http://coco.maltedmedia.narkive.com/2DM5LvJ2/color-
> basic-1-0-1-2-differen
>
>> >> ces
>> >>
>> >> which backs up some other information I found that the original 
1.0
>>
> ROM
>
>> >> did not support >16K memory fit but that the 1.1 ROMs do.
>> >>
>> >> Can anyone shed some light on this behaviour?
>> >>
>> >> Cheers,
>> >>
>> >>
>> >> Jon.
>> >>
>> >> --
>> >> == jon bird - software engineer
>> >> == <reply to address _may_ be invalid, real mail below>
>> >> == <reduce rsi, stop using the shift key>
>> >> == posted as: news 'at' onastick 'dot' clara.co.uk
>> >>
>> >>
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>> >>
>> >
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>>
>>
>> == mailto:jon at onasticksoftware.co.uk - in real life jon bird
>> ==  http://www.onasticksoftware.co.uk - stuff, on-a-stick
>> ==   "men love women, women love children, children love hamsters"
>> ==    <technology out of control>
>>
>>
>>
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> == jon bird - software engineer
> == <reply to address _may_ be invalid, real mail below>
> == <reduce rsi, stop using the shift key>
> == posted as: news 'at' onastick 'dot' clara.co.uk
>
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-- 
== jon bird - software engineer
== <reply to address _may_ be invalid, real mail below>
== <reduce rsi, stop using the shift key>
== posted as: news 'at' onastick 'dot' clara.co.uk