Path: vanilla!asbach!noris.net!blackbush.xlink.net!tank.news.pipex.net!pipex!btnet!zippy.dct.ac.uk!zippy.dct.ac.uk!nntp Newsgroups: comp.sys.sinclair Subject: A Question About T-States. Message-ID: <314801F7.41C67EA6@paisley.ac.uk> From: James McKay Date: Thu, 14 Mar 1996 11:24:39 +0000 Nntp-Posting-Host: diana16.paisley.ac.uk X-Mailer: Mozilla 2.0 (X11; I; SunOS 4.1.3 sun4c) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 17 Anyone who has used Z80 on the PC or x128 under Linux will know about the overscan screen, which seems to work reasonably for most things, but if you've ever tried part 2 of the Shock demo, the Overscan demo or some of the parts of the NMI 2 demo will have seen that the overscan is just too high up the screen, by quite a long way. Does anyone know why this is? Also the +2A manual says the Spectrum is 311 lines @ 228 t-states each. Z80 document says 312 lines @224 t-states each. XZX document (I think) says it times 69888 t-states (224*312). Which is true? -- James McKay, com40014@paisley.ac.uk ---- Path: vanilla!asbach!noris.net!blackbush.xlink.net!tank.news.pipex.net!pipex!warwick!bignews.shef.ac.uk!not-for-mail From: thdb86%teach@dcs.shef.ac.uk (Damion Yates) Newsgroups: comp.sys.sinclair Subject: Re: A Question About T-States. Date: 14 Mar 1996 17:23:17 GMT Organization: Department of Computer Science, University of Sheffield Lines: 32 Message-ID: <4i9km5$n5g@bignews.shef.ac.uk> References: <314801F7.41C67EA6@paisley.ac.uk> NNTP-Posting-Host: suna23.dcs.shef.ac.uk X-Newsreader: TIN [version 1.2 PL2] James McKay (com40014@paisley.ac.uk) wrote: : Anyone who has used Z80 on the PC or x128 under Linux will know about : the overscan screen, which seems to work reasonably for most things, but : if you've ever tried part 2 of the Shock demo, the Overscan demo or some : of the parts of the NMI 2 demo will have seen that the overscan is just : too high up the screen, by quite a long way. I commented on this ages ago. The second part of the shock megademo is one of the first tests I give to an speccy emulator. Others are ThrustII and PaperBoy these all have overscanning on common. On my 386dx40 and on the 486dx33's here at college, Z80 3.03 is about one line out. Thats pretty close if you ask me. On my +3 the demo was perfect and I was shocked when I saw it as I simply couldn't see the lines between border and screen! part 2 used a test to see whether it was on a +3 48k or any 128k (+2a=+3) all three were slightly different. Is this emulated ? : Does anyone know why this is? : Also the +2A manual says the Spectrum is 311 lines @ 228 t-states each. : Z80 document says 312 lines @224 t-states each. : XZX document (I think) says it times 69888 t-states (224*312). : Which is true? : -- : James McKay, : com40014@paisley.ac.uk -- Damion Yates - Sheffield Uni, UK. http://www.bath.ac.uk/~exxdmy ---- Path: vanilla!asbach!noris.net!blackbush.xlink.net!tank.news.pipex.net!pipex!warwick!bham!bhamcs!news.ox.ac.uk!news From: imc@ecs.ox.ac.uk (Ian Collier) Newsgroups: comp.sys.sinclair Subject: Re: A Question About T-States. Date: 14 Mar 1996 18:51:03 GMT Organization: Oxford University Computing Laboratory Lines: 25 Message-ID: <8084.imc@comlab.ox.ac.uk> References: <314801F7.41C67EA6@paisley.ac.uk> NNTP-Posting-Host: boothp2.ecs.ox.ac.uk X-Local-Date: Thursday, 14th March 1996 at 6:51pm GMT In article <314801F7.41C67EA6@paisley.ac.uk>, James McKay wrote: >Also the +2A manual says the Spectrum is 311 lines @ 228 t-states each. >Z80 document says 312 lines @224 t-states each. The 48K spectrum has 312 lines of 224 T-states each, while the +3 has 311 lines of 228 T-states each. As far as I know, the other 128K machines are like the +3 except that some of them are offset by one clock cycle. By my calculations, the +3 displays the first pixel of the screen 14368 T-states after the interrupt line is activated (that is, if you do an OUT to the border port which finishes 14368 cycles after the interrupt happens then the border change will be just `under' the first pixel of the screen). The equivalent number for the 48K is 14337 according to my calculations, which is 8 less than the value quoted in the Sinclair FAQ. I don't know which one is right! (If anyone wants to check, btw, note that an interrupt-mode-2 routine is entered 19 T-states after the interrupt occurs). Ian Collier - imc@comlab.ox.ac.uk - WWW Home Page (including Spectrum section): http://www.comlab.ox.ac.uk/oucl/users/ian.collier/index.html New to this group? Answers to frequently-asked questions can be had from http://www.nvg.unit.no/spectrum/ . Sam Coupé FAQ: http://www.soton.ac.uk/~tsp93/Coupe/FAQ.txt ---- Path: vanilla!asbach!noris.net!blackbush.xlink.net!howland.reston.ans.net!newsfeed.internetmci.com!xmission!inquo!nntp.uio.no!nntp.uib.no!nntp-bergen.UNINETT.no!nntp-trd.UNINETT.no!due.unit.no!pentagram.troll.no!nobody From: Arnt Gulbrandsen Newsgroups: comp.sys.sinclair Subject: Re: A Question About T-States. Date: 14 Mar 1996 21:15:35 +0100 Organization: Troll Tech AS, fax +47 22646949 Lines: 17 Sender: agulbra@pentagram.troll.no Message-ID: References: <314801F7.41C67EA6@paisley.ac.uk> NNTP-Posting-Host: pentagram.troll.no X-Newsreader: Gnus v5.0.13 James McKay > Anyone who has used Z80 on the PC or x128 under Linux will know about > the overscan screen, which seems to work reasonably for most things, but > if you've ever tried part 2 of the Shock demo, the Overscan demo or some > of the parts of the NMI 2 demo will have seen that the overscan is just > too high up the screen, by quite a long way. > > Does anyone know why this is? > > Also the +2A manual says the Spectrum is 311 lines @ 228 t-states each. > Z80 document says 312 lines @224 t-states each. Frode Tennebø told me it varies with the model, some are 224 and some 228, but I don't remember what model it changed with. Spectrum 128k maybe. --Arnt