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Forum Index : Microcontroller and PC projects : maximite colour computer
| Author | Message | ||||
| rambo55 Newbie  Joined: 11/12/2012 Location: AustraliaPosts: 15 |
I have the maximite colour computer with the pic32mx795f512L when I turn on the maximite and type memory it say 32kb ram should there be 128kb can any one tell me why there only 32kb |
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TassyJim Guru  Joined: 07/08/2011 Location: AustraliaPosts: 6098 |
The memory is shared with the Video memory which uses a lot in colour mode. If you switch to mode 1 (mono), the amount of available memory will be about 80kB Jim VK7JH MMedit MMBasic Help |
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Nick Guru Joined: 09/06/2011 Location: AustraliaPosts: 512 |
The PIC chip may have 128K but the BASIC interpreter software occupies some of that plus it reserves some for it's use (fonts, sprites, variables, screen buffer etc). Leaving you with round about 32K for your BASIC code. This is the case with all computers right back to the vintage days. It's a matter of TOTAL SPACE versus AVAILABLE SPACE. Nick |
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| rambo55 Newbie Joined: 11/12/2012 Location: AustraliaPosts: 15 |
yes it been so long back in the 80s when I had the Commodore64 Computer I forgot about the 64kb and the 38911 Free Ram and I write programmed for the C64 it bring back memory. |
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Juri74 Senior Member  Joined: 06/02/2012 Location: ItalyPosts: 162 |
commodore 64 display about 39kb free basic ram because the rest of the memory was overlayed by basic rom + kernal rom + io space + video & system reserved memory. in commodore 64 there was the ability to disable these roms to obitain more free ram to use only with ML programs.. the colour maximite doesn't have a "kernal" or "basic" rom that overlay free ram... i tried to turn off video (config video off command) and use it only through the serial usb connection (via tera term) but it still miss 20 kb of memory... (free memory is 107kb) why? memory
0kB ( 0%) Program (0 lines) 0kB ( 0%) 0 Variables 0kB ( 0%) General 107kB (100%) Free |
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CircuitGizmos Guru Joined: 08/09/2011 Location: United StatesPosts: 1425 |
RAM space that the firmware itself needs. Buffers and variables for USB communication, for example. Just the RAM space needed for MMBasic to operate, such as stack space. Micromites and Maximites! - Beginning Maximite |
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| MOBI Guru Joined: 02/12/2012 Location: AustraliaPosts: 819 |
Quibbling over a few K of memory!!! My first computer (Motorala 6800D2) had 128 BYTES of RAM and one could write usable programmes with it (in hex with a hex keypad). The Apple, if I remember correctly had 48K, and we did wonders with it. David M. |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3802 |
Bear in mind it's 32-bit chip with 32-bit integers and addresses (pointers). RAM goes fairly quickly. Some could be "saved" using offsets and extra arithmetic but it would run slower. The one chip does DMA for various things like video, making it simpler and cheaper. Think what the value of money was back then and what a C64 cost! Saving RAM mattered more. Does it matter now... A PIC32 895 or 995 or whatever, with 256K RAM, is to be expected. Geoff would have it working in about a day, maybe an hour, as a few tweaks to the C and it's done. John |
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Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9307 |
As others here have mentioned, RAM is shared. As others here have ALSO mentioned, this was the norm back in the day too. As with the Commodore 64, the Atari that I was so in love with(and so obviously still am!!!  ) had the ability to kill the BASIC in favour of a program in native machine code. From memory(if you'll pardon the pun!), you held down OPTION while you turned the Atari on, to disable BASIC.
The MM actually has almost twice the memory of the Atari 800XL and Commodore 64 which were both 64KB RAM machines. The MM ALMOST has as much RAM as the Atari 130XE which had 128KB of RAM, but still the same 6502 CPU. To get access to the upper 64KB(or lower depending on where you are counting from), the 130XE used a memory bank switching/manager chip called Freddie. Oh and MOBI: Quibbling over a few K of memory, as when you have limited resources you tend to be more concerned about losing a few K of RAM here and there.  Unlike today, where RAM generally is not that much of an issue, as you can buy a few more GB for very little cash. I know you were just making a tongue-in-cheek remark, so I am not trying to take you to task over it!  Smoke makes things work. When the smoke gets out, it stops! |
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