Hi, John, I am interested in 1 as well if it's not too late.
Regards, Brian On Monday, February 9, 2015 at 3:22:53 PM UTC-5, monahanz wrote: > > OK I have the following list for people that would like an S100 VGA video > board:- > > Fabio,3 > David ,2 > Todd,1 > Matt,1 > Andrew L., 1 > Neil,1 > Peter,1 > Elsid, 1 > Paul B., 1 > Gary, 1 > Peter Cole, 1 > John M.,4 > > So I will order 20 boards (2 extra). Will take 3-4 weeks. > Do NOT send any PP payments until you receive the boards. > Peter could you send me your shipping address. > > John > > > > > On Wednesday, February 4, 2015 at 11:45:09 PM UTC-8, monahanz wrote: > >> Well here it is after no less than 10 prototypes I'm delighted to >> introduce the first XVGA video board that sits in the S100 bus. See here:- >> http://s100computers.com/My%20System%20Pages/VGA%20Board/VGA%20Board.htm >> Scroll half way down the page. >> There is one major limitation with this S100 bus XVGA board, It will >> only work with our *8088 CPU board*. With that board as best I can tell >> it is rock solid running MSDOS with an S100 bus clock speed (PHI) of 8 MHz >> (i.e. a 24 MHz Oscillator on the board). It will *NOT* work with our >> current 16 bit CPU's ( the *8086*, *80286* or *80386*). The reason for >> this is due to the fact that these VGA chips (at least for the Cirrus & >> Trident chips), require the CPU to be able to send 16 bit data as two back >> to back 8 bit bytes. The chips actually have dedicated lines (MCS16* & >> IOCS16*) to flag the CPU to let it know it is capable of a 16 bit >> transfer. However I found out the hard way, that these chips do not always >> exercise this option -- particular during initialization. On our ISA >> converter board I played around with the circuit to sequentially send two 8 >> bit bytes using *Sergey's ISA Super VGA board* >> <http://www.malinov.com/Home/sergeys-projects/isa-supervga>. I could >> not find a reliable solution. The best effects were sensitive to the bus >> CPU speed and failed altogether at high MHz speeds. >> >> The fundamental problem was that these VGA chips can and do pull wait >> states on the bus at impossible to determine times (particularly during >> screen scrolls). The length of the wait states is highly variable. I >> concluded the only way to solve this is to redo the S100 CPU boards >> themselves so that if the 16 bit CPU board does not get a SIXTN* >> acknowledge from a sXTRQ* it proceeds to send two back to back 8 bit >> bytes. This was actually part of the IEEE-696 specification. However most >> manufactures at the time (an also in our cases), ignored this and simply >> supplied 16 bit capable RAM and/or IO boards. The only documented circuit >> I could find was the (excellent) one described for the *TecMar 8086 >> board* >> <http://s100computers.com/Hardware%20Folder/TecMar/8086%20Board/8086%20Board.htm>. >> >> >> >> The good news is that the 80486 CPU has the ability to *on the fly *send >> 8, 16 or 32 bit data depending on the chips on the receiving end. The >> other good news is that this XVGA board can send and receive 16 bit data. >> The chips themselves have 16 bit data pins so such a board should work at >> full speed with such a CPU. Most of the time transfers will be 16 bits but >> initialization and ROM access will be 8 bits -- just as in the IBM-AT box! >> >> I must point out however that currently this is all theoretical. I am in >> the process of building a knockout 80486 CPU board that should in theory be >> capable of working with any S100 board (old or new). If this does not come >> about then I would fall back to modifying some of our earliest CPU boards. >> - That's the plan. >> Anyway wanted to let the group know of the board. I will be doing a usual >> group order of bare boards in the next week or so. If interested please >> let me know. >> >> -- You received this message because you are subscribed to the Google Groups "N8VEM-S100" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
