Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!swrinde!cs.utexas.edu!sun-barr!newstop!sun!imagen!atari!apratt From: apratt@atari.UUCP (Allan Pratt) Newsgroups: comp.sys.atari.st Subject: Re: Atari TT Message-ID: <2954@atari.UUCP> Date: 3 Jun 91 20:20:26 GMT References: <91148.132622ONM07@DMSWWU1A.BITNET> <1884@richsun.cpg.trs.reuter.com> <17555@chaph.usc.edu> Organization: Atari Corp., Sunnyvale CA Lines: 46 baffoni@aludra.usc.edu (Juxtaposer) writes: > From the discussion on c.s.a.st a while back with Alan Pratt, I believe he >said that you can only have 4MB _ST_ ram. You can have 16 MB TTram like you >said, but that the other 6MB of ram comes from using the VME bus for ram >expansion. In fact, the VME ram is supposed to be faster than STram (no >sharing it with video, etc.), even though it is slower than TT ram. No, no, no... Your picture of memory in a TT and its limits is a little off. On the motherboard there are two megabytes of ST RAM. Period. No options, no extra SIMM or DIP sockets, no nothing. You can buy a 2MB ST RAM add-on card, for a total of 4MB of ST RAM. There may one day be an 8MB ST RAM add-on card, resulting in a total of 10MB of ST RAM. You can buy a 4MB TT RAM add-on card. It may be that, with some work, you can make this address 16MB of TT RAM. In future (now?) you can buy 16MB of TT RAM from Atari -- I'm just not sure. All of these boards are more than just RAM -- they also have memory controllers which you can't just get off the shelf. In the TT030, there is one VME slot, but it is not appropriate to put system expansion RAM there. The slot is for peripherals, not RAM. If you DO put RAM there, you have to tell the OS about it yourself, and it will be slow: it's not cacheable, it's only 16 bits wide, it's on the VME bus, and it's not SCSI-accessible (meaning transfers have to be use SCSI-accessible RAM; this is taken care of in the drivers, but it slows you down). I've put memory there to test things, and it is not fun. Things run DRAMATICALLY slower from that kind of RAM. It is not unreasonable to suppose that Atari may, in future, come out with a machine in the TT family which has full-featured VME, including the ability to put 32-bit, cacheable, OS-detectable, SCSI-accessible RAM on the VME bus. The TT is designed with this in mind, but the actual VME bus in the TT030 isn't capable of it. Such RAM would be slower than TT RAM (mainly because you can't do burst fills on the VME bus) and about the same speed as ST RAM: faster because it's not shared with video, but slower because it's on the VME bus. ============================================ Opinions expressed above do not necessarily -- Allan Pratt, Atari Corp. reflect those of Atari Corp. or anyone else. ...ames!atari!apratt