pevalcas pevalcas is offline Junior Member Join Date Mar 2011 Posts 7 Default Explanation on the various Olivetti monitors of the eighties Dear All, as I'm supposed to be one of the most knowledgeable on Olivetti computers ... I just explain and try to answer the questions raised in the thread. 1) Monitor 1 was a monitor for the Olivetti M240/AT&T PC6300 WGS)with the OGC (Olivetti Graphics Controller) P/N GO708. This was the implementation in a short ISA 8 bit card (using a large gate array and a chip from Paradise/WD), of the original M24 Video Board. It could also be used with the Olivetti M24 because the video interface was identical. The monitor is a 14" monitor (thus maximum 640 x 400 digital 4 signals TTL color monitor). The connector is DB25 male for the Olivetti/AT&T PC6300 graphic card. The advantage is it's a 14" instead than the original 12". So it's bigger and better readable. There were two versions. One with the icons as a circle (first version). The other was identical as the one in second picture. 2) Monitor 2 can be 3 different kinds. Either usable with Olivetti M240's or AT&T PC6300 WGS, with DB25M connector. In this case the model is CDU 14 1040. But it can be also be EGA to be connected with the OEC (Olivetti EGA Compatible Board) that was equipping M240, M250, M280, M290 and M300. In this case the connector is a DB9M. Model is CDU 1435 and it should be produced by Hantarex if I remember well. Third option, it could also be a monitor for the OVC (Olivetti VGA Compatible, or board code GO481). In this case the model number is CDU1431/HA21 (Hantarex, Italian monitor company located in Florence), or CDU1431/SA31 (Salora) or CDU1431/MA41 (Matsushita/Panasonic). I have all the 3 versions of the monitor. The best was the Salora, due to the construction and organization of the PCBs. The Salora has a retractible PCB that can be easily repaired. 3) The third monitor is monochromatic and was never produced as color monitor. it's too small to contain the electronics of a color monitor and the bigger picture tube. Also this one can be in different versions. Usually digital TTL with EGA resolution (Green, White and probably Amber) with a DB9M connector and Analog VGA (Paper White) with a DB15HDm connector. Olivetti M24 monochrome monitors were produced by Hantarex, Matsushita (but around 1986 this has been replaced by Goldstar). The monitor code was Always DSM2412B (Bianco/White) or DSM2412A (amber) or DSM2412V (verde/green). Amber was rare, and White was even more rare. I have 4 amber monitors and two white monitors. I am lucky. The Color monitor was the DSM2412C, manufactured either by Toshiba or by Mitsubishi. Both made in Japan. I have not less than 14 color monitors and all of them work after 30 years! They don't even suffer from capacitors dryness. IBM was using at that time for their PC Family (5150, 5160, etc), crappy color monitors made in Taiwan from Tatung or other companies. I only saw broken IBM PC color monitors. Internally they were messy with cables going everywhere. The AT&T PC6300 color monitor model CRT318T was identical to the Olivetti DSM2412C made by Toshiba. The CRT318H was probably from either a different producer, or completely different. The other monitor, compatible with the VDC750 (I have 3 of them), was the CRT319 and was an EGA manufactured expressely for AT&T. I never got an AT&T CRT319 so I don't know. I hope I was able to explain it for everybody. Feel free to ask more. Regards, Vincenzo. AT&T PC6300 Quick reply to this message Reply Reply With Quote Reply With Quote Multi-Quote This Message Blog this Post February 8th, 2017, 05:41 PM #29 pevalcas pevalcas is offline Junior Member Join Date Mar 2011 Posts 7 Default Hey Dwight ... I'm Vincenzo from Italy. I have around 40 M24 and 35 M20, including 3 or 4 with an hard disk). I appreciate the work you did to add an hard disk to the Olivetti M20. No, the Olivetti M24 monitor is different from the M20 one. M24 color monitor was produced by Toshiba and Mitsubishi. The M20 one was produced by NEC. The frequencies are different, too. M20 resolution was 512 x 256 and the dot clock frequency is 19Mhz. The Olivetti M24 was 640x400 and has a dot clock frequency of 24Mhz (taken from the oscillator on the motherboard, depending on the jumpers on the video board). Or from the external video expansion board. If in the Olivetti M24 you have installed a Z8000 board, this will supply a 19Mhz oscillator. In such case the software can switch to the frequency coming from the external video card (EGC2413) and emulate the resolution of the M20. The Mode1 Output Port located at 3DEh has a bit to switch to the external dot clock. In fact ... the monitors for Olivetti M24 are "bi-frequency" and can work with both a dot clock of 24Mhz (for 640 x 400 resolutions) or 19Mhz, when emulating the M20. The only doubt I have are the impedences, the interface of the 4 video signals, the HSYNC and VSYNC etc. The risk is the match of impedences between an M24 monitor connected to an M20 would burn the input stages. I should be needed to have both the electric scheme of both monitors and output stages of the graphics boards. Hope it's clear now! Regards, Vincenzo. ath: utzoo!attcan!uunet!husc6!bloom-beacon!gatech!bbn!rochester!ur-tut!aptr From: aptr@ur-tut (The Wumpus) Newsgroups: comp.sys.att Subject: VDC750 for 63xx - I finally tried one Keywords: EGA, CGA, Video Cards Message-ID: <2114@ur-tut.UUCP> Date: 24 May 88 22:49:25 GMT Organization: Univ. of Rochester, Computing Center Lines: 31 Well, I finally got a chance to try the new AT&T VDC750 card. So far I have tried it with in a 6300 WGS and used both an AT&T 319 monitor and a Xerox color monitor from a Xerox 6064 (yet another relabeled Olivetti M24) that appears to be internally identical to the 318 monitor. The 319 handled EGA modes better then the Xerox monitor. EGA came out slightly squished (about 85% normal height) on the Xerox monitor, but worked perfectly on the AT&T 319 monitor. The VDC 750 supports all EGA modes along with all of the graphic modes that came on AT&T's Indigenous Display Card (CGA, 640x400 monochrome). It does not support AT&T's Diplay Enhancment Board's 640x400 16 color mode, but does offer this as an extended EGA mode (using different drivers). I have yet to try the car in an old 6300, but I will probably post my results when I ge a chance. Summary: The VDC750 display card appears to be one of the easiest ways to add EGA capability to a 6300 without having to replace the monitor that came with the 6300. The board lists for $500. It does suffer from the same problems that all EGA cards used in the 6300. The problem stems from poor programming practises on the part of many programs. The board does come with a set of patches for Microsoft Windows and AutoCad to allow them access to its 640x400 16 color mode. -- The Wumpus UUCP: {cmcl2!decvax}!rochester!ur-tut!aptr BITNET: aptrccss@uorvm Internet: aptr@tut.cc.rochester.edu Disclaimer: "Who? When? Me? It was the Booze!" - M. Binkley