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My first 800XL - Couple of basic questions


800_Rocks

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I've had my 800 (still works great) since 1982.  I purchased locally an 800XL, a good working 1050, and a 1025 printer of unknown condition (wow it is heavy).  The 800XL and 1050 are nice, I opened and cleaned them real good and turned the 1050 into my new Happy drive (moved the Happy card from another 1050 that needs a belt).  Given I am new to the 800XL I have a couple basic questionsThanks in advance!  Some attached pictures to go along with some my questions.

 

1) RF gives a nice color but the image is somewhat fuzzy as RF tends to be.  I tried both channel 2 and 3.  I have a good working composite to S-Video cable that works great with my 800 and gives great image quality.  However, when I use this composite cable on the 800XL the image is much sharper than with RF however there is no color via composite.  Only shades of grey.  Is this expected or do I have an issue?

 

2) The 800XL sound, memory and keyboard tests all check out however, I only count 48 little squares for the RAM test.  How come only 48 when there should be 64K of RAM?  Also, what do the two long green bars represent for the ROM test (the left bar vs the right)?

 

3) Given my 800 has only 48K I'm curious about the 800XL's extra 16K (64K total).  Do I need to do anything special to utilize the extra 16K?  OR Is it always available or is it only there for a Ramdisk?

 

4) What should the BASIC command 'PRINT FRE(0)' display on an 800XL?   Mine shows '37902' on the 800XL with no cartridge and nothing on SIO.  Incidentally this is the same number that displays on my 48K 800, '37902'.  So where's the extra 16K of the 64K 800XL?

 

5) Looking at the Keyboard Test.  I understand most everything but have some questions:

    -  Nothing displays or beeps when I press the Break key.  Is that normal?  Note: The Break key works as expected in BASIC.

    -  Nothing displays or beeps when I hold Control and press '1'.  Both in the keyboard test and when in BASIC.  Is that normal?

    -  Which keys or key combinations do you hit to test the characters on the top row of the keyboard test? (see picture)  I can get some of them to register (START, SELECT, OPTION and the Inverse key).  However, the following are a mystery (are show in inverse on the top row):  The 'R' in the top left.  The 1, 2, 3, 4, H and B characters (on the top right).

 

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1) Composite on the 800XL should look the same as it does on your 800. B&W indicates on the Luma signal is coming through. If you're using a cable with 4 separate RCA plugs, make sure you're not accidentally using the Luma plug in the Composite jack. TANGENT: for unknown stupid reasons, Atari decided to omit the Chroma (color) signal from the DIN video jack, so S-video or separate chroma/luma displays won't work properly. You have to add a single wire to the XL motherboard to reconnect the chroma line, but it's an easy mod. 

 

2) The memory test results are normal. Atari's stock OS recognizes only the same 48K RAM as on the fully-expanded 800. There are two ROM blocks for the two ROM chips - OS and BASIC. 

 

3) The extra 16K is mostly unusable to users absent special programming tricks. If the OS is turned off and switched out of the memory map, a clever programmer could replace the OS ROM with routines more suited to his or her purpose - some games did this, if I recall correctly. For the average home programmer it might as well not have been there since it was generally not accessible. An expanded machine (with an internal or PBI connected memory expansion) can run a small group of later-era and modern programs that can use the extra memory.

 

4) The BASIC free memory command should give the same result for an 800 as your 800XL.

 

5) It's been awhile since I bothered with the XL Self-Test screen, but R is System Reset, 1 - 4 represent the 1200XL function keys, which are not present in the 600XL or 800XL. Can't recall off-hand what the others indicate. If the keys all work when you type them in BASIC, you're fine. 

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Ugh, first time posting since the forum software update. The "Quote"
button is gone, so I can't reply to you point-by-point...

The 6502 used in the Atari computers can only address 64K of memory,
which includes RAM, ROM, and memory-mapped I/O (e.g. the Atari's POKEY,
ANTIC, etc chips take up address space).

The extra 16K is "hidden", it uses the same address space as the OS
ROM. To access it, software has to temporarily disable the ROM. Most
software written back in the day doesn't use the extra 16K because (a)
it requires extra programming to switch the OS on & off, and (b) there
were lots of 800s out there still, using the extra XL RAM would mean
the software wouldn't run on an 800.

The self-test only tests the first 48K if the built-in BASIC is disabled,
or the first 40K if it's enabled. The two long bars each represent half of
the 16K ROM. It's divided in half because the memory-mapped I/O is mapped
to the middle of the ROM area... fun fact: the 64K XL/XE machines are
really only 62K, because there's no way to disable the 2K I/O window. The
other 2K of RAM is physically present but impossible to access.

The keyboard test shows the keyboard layout of the 1200XL, which has
extra function keys F1 to F4. That's what the mysterious 1 2 3 4 across
the top are supposed to represent.

R is Reset, and can't be tested by the keyboard test because when you
press it, it resets the system. H is the Help key, which exists on the
800XL but is located in a different place.

It's normal for the Break key not to show up in the keyboard test. Also
Ctrl-1 is the "pause the screen" key, it's not surprising that it doesn't
do anything in the keyboard test.

Hope this helps.

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5 minutes ago, Urchlay said:

Ugh, first time posting since the forum software update. The "Quote"
button is gone, so I can't reply to you point-by-point...

 

3 minutes ago, flashjazzcat said:

You can. Highlight the passages you wish to quote, and click the 'Quote' button which pops up.

Might be a browser or forum skin issue. The Quote button is right where it's always been for me, with the Multi-Quote ("+") button right next to it.

 

image.thumb.png.6aa8c48e99de33a86fb9470355e12d7f.png

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I highlight what I want to quote within a post and wait a moment, 'quote selection'      will pop up , I click it. so you can select parts of a post that way to quote and answer.

 

The button at the bottom of the edit window is to + add multiple full posts as quotes, or you can just select Quote button that is next to the + to quote a singular full post.

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Since the 400 and 800 were out for so long 48k was standard.  The extra 16k was a "hack" so it wasn't readily avail.  Special code had to be written to use it, which it was in the later years.  Most games only used 48k due to the fact that they wanted it to run on all Atari computers.  The market at large since the 800 had 48k and the 400 could be upgraded to that as well.

 

You might need to do the Chroma hack on the 800XL and also remove C56 capacitor to sharpen the image.  See here for a great video mod you can do.

 

https://atariage.com/forums/topic/41580-quick-easy-video-upgrade-for-800xl/#comments

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