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Offline Michael_Lee

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Give a summary of RAM?
« on: April 09, 2011, 03:35:20 pm »
Can somebody give me a quick summary on how memory in RAM is organized, or suggest a good guide?

Specifically, which portions of RAM are free RAM, which parts should I generally leave alone,  which parts do the OS use (and for what purpose), which parts does Axe use, where is the VAT located, etc...
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Offline Munchor

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Re: Give a summary of RAM?
« Reply #1 on: April 09, 2011, 03:37:46 pm »
Quote
When the CPU executes a program, that program is stored in the computer's main memory (also called the RAM or random access memory). In addition to the program, memory can also hold data that is being used or processed by the program. Main memory consists of a sequence of locations. These locations are numbered, and the sequence number of a location is called its address. An address provides a way of picking out one particular piece of information from among the millions stored in memory. When the CPU needs to access the program instruction or data in a particular location, it sends the address of that information as a signal to the memory; the memory responds by sending back the data contained in the specified location. The CPU can also store information in memory by specifying the information to be stored and the address of the location where it is to be stored.

A general text on RAM. Concerning calculator RAM, I'm not your guy.

EDIT: The text, I found it here.
« Last Edit: April 09, 2011, 03:38:07 pm by Scout »
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Offline Michael_Lee

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Re: Give a summary of RAM?
« Reply #2 on: April 09, 2011, 03:41:16 pm »
Well, that's a bit too general for me.

I'm looking for specifics about the TI-8x branch of calcs.
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SirCmpwn

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Re: Give a summary of RAM?
« Reply #3 on: April 09, 2011, 03:43:41 pm »
Look here and here.
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Ashbad

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Re: Give a summary of RAM?
« Reply #4 on: April 09, 2011, 03:45:04 pm »
I don't really have time to say a ton, but:

At the very end of RAM is the location of the stack -- usually in the $FFEx - $FFFx region.  Just behind that is the VAT, which is in most of the $Fxxx region.  jumping to the beginning of RAM, are places not to touch -- safer areas start popping up at around $8000.  There's a few big pockets between $8700 and $9200, which is around the area SaveSScreen and Appbackupscreen are located.

I know there are tons of more areas, but I forget their exact addresses.  Most of them appear in the $8500 - $9C00 range, though.

Maybe someone more experienced can give you a more complete layout ;)
« Last Edit: April 09, 2011, 03:46:02 pm by Ashbad »
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Offline Freyaday

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Re: Give a summary of RAM?
« Reply #5 on: April 10, 2011, 02:02:49 am »
TI's 83+ developer's guide is quite thorough and seems to have been made before they became evil. I'm pretty sure you'll find what you need in there, somewhere. It is something of a challenge to comprehend, though, slightly below The Scarlet Letter in difficulty, and the diagrams are confusing at times, but everything should be in there. I don't know for sure, though, as I haven't read the whole thing through. A Google search will turn up the PDF.
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Offline thepenguin77

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Re: Give a summary of RAM?
« Reply #6 on: April 10, 2011, 06:47:02 pm »
Here is where you can find the pdf Freyaday is talking about. This page has some other cool stuff on it too.

SirCmpwn's second link is good, but it's not very thorough. If you really want to know what memory is where check out BrandonW's ti83plus.inc, and scroll down to the ram areas. I honestly open that file almost every day.

As for which ram areas are safe. Going by brandonW's list:
appData, RamCode, any MD5, tempSwapArea, OP's, iMathPtr's, textShadow, saveSScreen, statVars, smallEditRam, cmdShadow, appBackUpScreen, and last but certainly not least, almost the entire extra ram page

Each one of those has specific times it will get killed though, although if you think about what bcall's you are using, you can probably figure out if it's going to get killed or not.

I'm sure I missed a few also ;)
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SirCmpwn

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Re: Give a summary of RAM?
« Reply #7 on: April 10, 2011, 06:47:50 pm »
Don't forget, though, no extra RAM on TI-83+ BE.
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Offline willrandship

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Re: Give a summary of RAM?
« Reply #8 on: April 10, 2011, 06:51:20 pm »
just like the normal 83+ then? Not the SE?
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Offline DrDnar

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Re: Give a summary of RAM?
« Reply #9 on: April 10, 2011, 06:54:19 pm »
The TI-83+SE is much more like the TI-84+SE than the TI-83+. It was like a beta version of the TI-84+SE. It has the full 128 K of RAM, the faster CPU, the crystal timers, and most of the extra ports. The only thing it's missing is the USB hardware and RTC.

Oh, yeah, so read this:
(20:56:21) DrDnar: Ah ha, assuming you don't use the crypto or small edit buffer bcalls, there's over 512 bytes free at 8000h.
(21:03:53) DrDnar: The TIOS programmers were nothing if not generous in reserving memory for OS use.
(21:05:47) DrDnar: BrandonW: Is the area marked smallEditRAM entirely free?
(21:06:15) BrandonW: There's actually 1087 bytes free if you rebuild the app base page table when done.
(21:06:38) DrDnar: Contiguous?
(21:06:59) DrDnar: I assume there's a bcall to rebuild the app base page table.
(21:07:18) BrandonW: Yes, and the BCALL is 5011h.
(21:07:22) BrandonW: I called it _FillBasePageTable.
(21:07:50) BrandonW: And yeah, it's free if there's no small edit buffer going on, such as when TRACEing.
(21:08:48) DrDnar: Well, between appBackupScreen, saveSScreen, graphScreen or whatever, and the 8000h area, there's more than enough free RAM for dynamic four-level grayscale.
(21:10:15) DrDnar: The bottom line is, there's craploads of free RAM available for use if you know where to look.
« Last Edit: April 10, 2011, 06:55:03 pm by DrDnar »
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Offline willrandship

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Re: Give a summary of RAM?
« Reply #10 on: April 10, 2011, 06:59:03 pm »
Well, it was much more of a Special edition than the 84+ SE was to the 84+ :P
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Offline Munchor

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Re: Give a summary of RAM?
« Reply #11 on: April 12, 2011, 07:34:13 am »
83+SE is better than 84+SE?

Or is it just better when compared to 83 and 84 respectively?
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Offline JosJuice

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Re: Give a summary of RAM?
« Reply #12 on: April 12, 2011, 09:06:26 am »
Quote from: Scout on April 12, 2011, 07:34:13 am
83+SE is better than 84+SE?
No (unless you have one of those 84+SEs with bad LDC driver and RAM :P)
Quote from: Scout on April 12, 2011, 07:34:13 am
Or is it just better when compared to 83 and 84 respectively?
Yes.
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Offline Munchor

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Re: Give a summary of RAM?
« Reply #13 on: April 12, 2011, 09:09:37 am »
Quote from: JosJuice on April 12, 2011, 09:06:26 am
Quote from: Scout on April 12, 2011, 07:34:13 am
83+SE is better than 84+SE?
No (unless you have one of those 84+SEs with bad LDC driver and RAM :P)
Quote from: Scout on April 12, 2011, 07:34:13 am
Or is it just better when compared to 83 and 84 respectively?
Yes.

I have a 84+ Keypad, which is *supposed* to be a 84+ SE, but isn't really in fact.

Thanks.
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Offline Michael_Lee

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Re: Give a summary of RAM?
« Reply #14 on: April 12, 2011, 09:28:04 am »
Cool, thanks.

I'll check those links out.
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