[Coco] Patching NitrOS9 for 8 meg

[Bill Pierce]

Doug, I wondered the same thing until it was explained to me, then I got involved with the NitrOS9 development and saw for myself, the whole problem with more than 2 meg of memory is the size of the memory map table kept in system memory. Even just at 4 meg, the table grows to be twice what it is. At 8 meg it's 4 times as large!!
If I remember correctly (correct me if I'm wrong), the memory allocation table is 256 bytes, which is 1 byte per 8k block (8*256=2meg). A memory map for 8 meg would take up 1k of system space and right now, system space is valuable.
There are probably ways around this, but would most likely involve a major rewrite of how the map is accessed. As for actual access to the memory, only minor patching would be needed.

In the Coco3FPGA project (mem at 5.5 meg), Dave Philipsen and I have written code that "illegally" accesses memory above 2meg (therefore not interrupting NitrOS9's mapping) to create a BMP viewer that loads 20+ 640x450 bmp files into memory, creates and displays a 640x450 256 color graphics screen (exclusive to the Coco3FPGA), then runs a "slideshow" routine scrolling through the pictures. This is done using standard CC NitrOS9 L2 and since NitrOS9 knows nothing of this graphics mode or the memory used, <CLEAR>ing to another window while it is running is disastrous... but it works!!
I would love to see NitrOS9 using more than 2 megs of memory, but until someone is adventurous enough to rewrite the way memory is mapped, I don't see it happening.
As for "Do we need more than 2 meg", I'll put it this way... until you have it, you'll never know how much you needed it until it's gone. I have a 1 meg Coco3, a 512k Coco3, and 5.5 meg Coco3FPGA, not to mention I run VCC at 8 meg (using only 2 meg with NOS9)... When I run my 512k Coco3, using my "normal" software development tools, I quickly run out of memory because I am used to being able to open more windows and run more apps on my VCC 2 meg system. What the hell am I running that uses so much memory you ask? Well, I usually have 3-4 graphics oriented text editors at 32k per screen plus program size and buffer allocation (basically 64k each), a window to run my C compiler (80 col HW text), and I'm constantly opening another 32k window to test my software (usually my MShell project) which can easily use up 512k without trying hard.
Yes, I'll take 8 meg any way I can get it!!

 

 

Bill Pierce
"Charlie stole the handle, and the train it won't stop going, no way to slow down!" - Ian Anderson - Jethro Tull

My Music from the Tandy/Radio Shack Color Computer 2 & 3
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-----Original Message-----
From: Doug Fraser <frase072 at telus.net>
To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
Sent: Thu, May 3, 2018 3:03 am
Subject: Re: [Coco] Patching NitrOS9 for 8 meg

Dave,Several years ago I had a Disto 1meg that was modified to do 2meg. When that upgrade eventually failed and was left with only 512k that was disappointing, to say the least. I was never able to get my hands on Disto 2 meg board. With the anticipation of the CoCoMEM board, I will have access to more ram. If what I've read is true, then it is cheaper to have a board with 8 meg as opposed to 2 meg. Hence my question. Sent from my Samsung Galaxy smartphone.-------- Original message --------From: Dave Philipsen <dave at davebiz.com> Date: 2018-05-02  22:35  (GMT-08:00) To: coco at maltedmedia.com Subject: Re: [Coco] Patching NitrOS9 for 8 meg Ok, I'm not trying to be mean-spirited but my question is this: Have you come to a point with the current 2MB limit where you are actually in need of more memory?  If so, what is the application?DaveOn 5/2/2018 9:57 PM, Doug Fraser wrote:> When the CoCoMem project becomes available, how difficult would it be > to patch NitrOS9 to access, say 8 meg of memory?>> Doug>>-- Coco mailing listCoco at maltedmedia.comhttps://pairlist5.pair.net/mailman/listinfo/coco-- Coco mailing listCoco at maltedmedia.comhttps://pairlist5.pair.net/mailman/listinfo/coco