randy@nlm-vax.ARPA (Rand Huntzinger) (09/24/85)
This is in response to an article by Rex Ballard which was a reply to a reply on Amiga memory management. Since the topic is the Atari ST I decided to post it here under a more suitable title. While I'm at it, I'll address a few points about the ST where there seems to be some confusion. In article <270@ccivax.UUCP> rb@ccivax.UUCP (rex ballard) writes: > >"Presenting the ATARI ST" has a memory map on page 34 that show address >$FF8000-$FF8200 labled "DATA CONFIGURATION", in the I/O region. If that >ain't an MMU term, what is? (Interesting 512 bytes - 512K hmmm), if they >send you a 68010 with your next OS, watch out!!!. Anybody look at those >addresses? > >If this is the case, does that mean that the 512K in the machine is >really the CACHE for an external RAM disk? > The schematics provided with the developer's kit does include a MMU chip, I haven't looked under the hood but by all reports it's there. Also, the machine was described as a 68010 based machine at one point in the documentation. This means they at least thought 68010 at one time, but doesn't indicate whether that might be a future upgrade. ----- You also mentioned TOS, which is reportedly a version of CP/M-68K. According to the documentation I have, it is not. TOS is a variant of a Digital Research operating system called GEMDOS, which looks very much like a 68K implementation of MS-DOS (or PC-DOS if you prefer). Like MS-DOS, it has a subset of commands which are CP/M compatible. The remaining entry points appear to be MS-DOS compatible. This must have been quite a help in porting GEM to the 68000. I expect we'll see GEMDOS appearing on other machines as well. I don't have documentation on the PC-DOS bios, but I wouldn't be a bit suprised if the Atari BIOS resembles it in some form. In the HitchHikers Guide to the Bios, there are mention of things like "IBM-PC compatible keyscan codes". It appears that it should be comparatively easy to port programs between the Atari ST and the IBM-PC. ----- Despite comments to the contrary, the Atari ST operating system does not have GEM and the operating system squished together. According to the documentation you can boot the system without all of GEM and the desktop. I haven't tried this, but it is documented. A MS-DOS like command processor is available with the developers package which can run on top of the desktop or in its place. Also, you do not have to include GEM commands in your applications to be able to run an application on the desktop. If your program doesn't use GEM, you can flag it as a TOS application and when it is started from the desktop the screen will clear and the program will run as if GEM wasn't there. If you write in C, you can use the standard I/O library to write to the screen. ----- Hopefully this will clear up some misconceptions about the ST and not introduce any misconceptions of my own. Rand Huntzinger
randy@nlm-vax.ARPA (Rand Huntzinger) (09/25/85)
> > The schematics provided with the developer's kit does include a MMU chip, I > haven't looked under the hood but by all reports it's there. Also, the > machine was described as a 68010 based machine at one point in the > documentation. This means they at least thought 68010 at one time, but > doesn't indicate whether that might be a future upgrade. > > --- More miscellaneous comments --- > > Hopefully this will clear up some misconceptions about the ST and not introduce > any misconceptions of my own. > > Rand Huntzinger Oops, I blew it and added at least one misconception. I remembered the mention of the 68010 as being in the machine area of the documentation, but I was wrong. It was under GEMDOS, which is not specific to the ST. There is no mention of the 68010 in the hardware section (Atari specific) in the documentation and any speculations I made concerning that are foolishness. Rand Huntzinger