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Decibels
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Joined: 16 Aug 2002
Posts: 1623
Location: U.S.A.
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 Posted: Sat Jan 17, 2004 10:38 pm Post subject: |
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deLockloire, since you fixed the error in the tutorial I found and changed it to 64KB, have you tried a higher setting? You don't mention it, so asking. Maybe the 64B wasn't an error, it might have been written when video cards had less memory?! Just an idea.
| Quote: | | Recent kernels that have the VGA Console driver can use dramatically more memory for scrollback, provided that the video card can actually handle 64 kb of video memory. Add the line: |
I wrote him a email, asking if that should be corrected in his FAQ.
I would assume that if you have a modern video card you could set it higher, like 640KB or more. That might be worth some investigation! 
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Support bacteria – they’re the only culture some people have.”
– Steven Wright |
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deLockloire
n00b
Joined: 10 Dec 2003
Posts: 62
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| Posted: Sun Jan 18, 2004 2:46 am Post subject: |
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| Decibels wrote: | | I would assume that if you have a modern video card you could set it higher, like 640KB or more. That might be worth some investigation! |
i may be so. i doubt that any other settings would do, since there is a part in the the vgacon.c which deals with what exactly should happen if this option is set ("#Ifdef VGA_CAN_DO_64KB", etc. etc.). it determines the begining and end of the memory addresses, which i don't know how to set and there're 2 other lines i have no idea what to do with. however, it's worth looking into, so i'll do that |
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Decibels
Veteran
Joined: 16 Aug 2002
Posts: 1623
Location: U.S.A.
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| Posted: Sun Jan 18, 2004 3:03 am Post subject: |
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Just glancing at it. Not real great at C, but believe 64K = 65536 so if double it to 128K = 131072 .
b0000 - a0000 = 1000 which is 65536 in decimal
so
c0000 - a0000 = 2000 which is 131072 in decimal
So might get away by just changing the one line:
| Code: |
#ifdef VGA_CAN_DO_64KB
/*
* get 64K rather than 32K of video RAM.
* This doesn't actually work on all "VGA"
* controllers (it seems like setting MM=01
* and COE=1 isn't necessarily a good idea)
*/
vga_vram_base = 0xa0000;
vga_vram_end = 0xb0000; |
TO
| Code: | #ifdef VGA_CAN_DO_64KB
/*
* get 64K rather than 32K of video RAM.
* This doesn't actually work on all "VGA"
* controllers (it seems like setting MM=01
* and COE=1 isn't necessarily a good idea)
*/
vga_vram_base = 0xa0000;
vga_vram_end = 0xc0000; |
As long as it doesn't conflict with anything else, should get away with it. Bamb, more scrollback.
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Support bacteria – they’re the only culture some people have.”
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deLockloire
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Joined: 10 Dec 2003
Posts: 62
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| Posted: Sun Jan 18, 2004 8:28 pm Post subject: |
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| Decibels wrote: | | As long as it doesn't conflict with anything else, should get away with it. Bamb, more scrollback. |
eh, encouraged by this idea, i said to myself, "why not 256k then?" so i've changed the original 2 lines to | Code: | vga_vram_base = 0xa0000;
vga_vram_end = 0xe0000; |
since e0000 - a0000 is 262,144 (256k) in decimal. greedy, eh? it just didn't work. so i gave up my greed and defined c0000 (as u originally suggested), but it didn't work either. then i realized that there're some other lines that define memory blocks, so, without having the slightest idea what i was doing--for me it's like dabbling in the occults, i adjusted these addresses to match with the c0000 mem setting (so there'll be no conflicts), and lo and behold, as it can well be expected (and sorry about the anticlimax) it didn't work either.  in case u're interested, i describe my results (in order of appearance ), also, i used the script i quoted from linuxquestion.org (see my post above):
1. some good scrback lines (317)
2. a few pages of blank greyness
3. greyness with black blocks and an increasing number of nice colorful flashing characters
4. a c64-like casino effect (colorful, flashing, etc.) this seems to be ordered in a mountainlike pattern, which is reoccurring
5. blackness with a few dispersed colorful chrs
6. then the line count continues (from 1,546-1,614), but they are indented to the 1/3rd of my screen
7. it starts all over again (from 1-5), but indented
8. the end is a normal appearance of lines 1,546-1,614 (not indented this time)
after this pretty nice and "professional" description, i'm just curious whether it's only my vga (asus v3800 tnt2) that doesn't support this. so if u (or anyone else following this thread) have tried it, would u plz post if it was a success, or the same as me. thx. |
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mingus
n00b
Joined: 10 Mar 2004
Posts: 11
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| Posted: Wed Mar 10, 2004 8:23 pm Post subject: |
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I've compiled fb in my kernel 2.4.25 and its works fine with the vga=791 option for grub. 
 To my question: how do I change the console to display 124x40 character instead of 128x48? The latter end up in to a very small text and the text tanger the edge of the screen. I've a LCD-monitor and the imagesize is fixed. On the 1.4 LiveCD all looks really fine (124x40);
'Console: switching to colour frame buffer device 124x40'
I'll hope that someone can salvage my little problem.. |
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Gentree
Watchman
Joined: 01 Jul 2003
Posts: 5350
Location: France, Old Europe
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| Posted: Fri May 07, 2004 11:42 pm Post subject: |
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Firstly thanks to all constructive contributions to the scrollback issue. This is a great help.
For those who still cant see why it would be useful , say you want to debug the boot process. You cant start anything because even root is not logged in , and dmesg is fine but is NOT a true copy of what is sent to the screen on boot up.
That was my primary need for bigger scroll-back.
As for firing up X and KDE to run a terminal emulator... I must be dreaming.... after that I will reboot to windowsXP Pro and start microsoft office to print my mate's new phone number on a sheet of A4 paper !
Thanks again to those of emence tolerance and wisdom who have found a solution in the source. This is impressive, open source and peer support: power to the people!!
Nice work .
[edit] PS The other point I wanted to make was poking around with the ammount of memory allocated other than by this compiler variable is DUMB! You have NO idea of the repercussions of that unless you have studied the rest of the code and are familiar with the kernel. Nuf sed?! 
Linux is stable , lets keep it that way. |
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