Re: [cc65] Banking out ROM (was: TGI preview)

From: Daniel Serpell <>
Date: 2009-11-15 01:58:29

On Sat, Nov 14, 2009 at 8:19 AM, Fatih Aygün <> wrote:
> Shawn Jefferson wrote:
>> Does the built-in config still have the start of RAM at $2E00 ?  You can get away with $2000
>> for most DOSes in wide-spread use.  The extra RAM was for any drivers (like the 850) that
>> might be loaded low (from what I recall.)  I always change it to $2000 myself.
> Yes, it's still $2E00. Sometimes I even go with $0600 :) Some emulators have a dos in the rom
> and others have virtual hard disks. On the real hardware, I have an sio2pc program and a virtual
> dos (I call it PseuDos) that just forwards the requests to the PC in the shortest possible time and
> allows me to load as low as $800 :)

Do you have that available somewhere? sounds interesting!

> I know MyDos 4.5 allows as low as $1F00. Do you know what's the lower limit for Dos 2.0s and
> Dos 2.5?

DOS 2.5, 2 drives, 3 max open files: $1C6C
DOS 2.5, 4 drives, 3 max open files: $1D8C (standard configuration)
DOS 2.5, 2 drives, 7 max open files: $1E6C
DOS 2.5, 4 drives, 7 max open files: $1F8C (max configuration)

I tested various DOS2.0 disks, and the numbers are similar to dos2.5
with 3 max open
files, but it's difficult to know as I don't have any "original" dos 2.0 disk.

In MyDOS each file buffer uses 256 bytes, so configuring it with 7
open files gives
a MEMLO of $22E8, really high, but it's $1EE8 with default config.

Also, BW-DOS 1.3, with up to 5 open files and 5 drives gives a MEMLO of $1EE4,
and increases to $1F42 if you load rtime8 real time clock driver.

So, I think that using $2000 as load address is the best option, and
the space from
MEMLO to $2000 could be addded to the heap.

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Received on Sun Nov 15 01:58:36 2009

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