I know the EGA Wonder 800+ doesn't get much love around here but so far it's been compatible with every game I've tried -I need to test more when I have access to it. The jumperless feature and the ability to display hi-res EGA or other modes on a plain CGA monitor is a cool little trick.

On another note and to follow with the original topic, I've tried an EGA card (PEGA2A based) with a Pentium MMX (2x50Mhz FSB) with caches off and the system POSTs with no issues. So I guess it's actually possible to use EGA in a much faster system than it was designed for.

Hi MMaximus, sorry to comment on an old thread, but I'm building my own 8088 (V20) based PC and I've got a PEGA2A based EGA card which works great at the normal 4.77MHz, but has post issues at 13.33 MHz Turbo mode I'm trying to implement. On your fast PCs, do you know what the ISA speed is on those motherboards?

I've got 24 and 30 MHz crystals coming to test at 8 and 10MHz Turbo also, I'm crossing my fingers that one of those will work. I'm a little confused by it as I have tried at 4 Wait States for IO requests but it can't keep up - might be the Video Memory reads/writes that are causing me trouble as they are not IO requests at are operating at 0WS at the moment (except for BUS_READY signals from the card which slow it down).

Cheers,
Chris!

Predator99 wrote on 2018-01-31, 18:13:

Yes, EGA should work in all boards with ISA slots, but I also noticed some incompabilities with card/board combinations

IMG_0653r.jpg

Make that all boards that recognise video card in an ISA slot at all, by later PCI/AGP boards, that wasn't a given. Particularly if it had onboard vid too.

Murugan wrote on 2020-05-06, 10:09:

As I found out, for some strange reason, my Olivetti monitor (according to the scarce info on the net) is EGA but only shows image when I hook it to the Olivetti that it came with.
On my IBM EGA and a EGA Wonder, only a scrambled line. My 5153 shows both an image when I confugure them for CGA.
Didn't know monitors could be picky.

Yeah, the monitors that came with the Olivetti M24 (as well as the AT&T 6300, which is exactly the same system sold under another brand) could work with *some* specific EGA cards, including the EGA Wonder 800 (not the 800 Plus, if I remember correctly). The STB Multires card might work as well.

It will not work with the original IBM EGA card, or on most other EGA clone cards.

The reason for this is because this monitor runs at 25kHz, as opposed to CGA (15kHz) and EGA (21.8KHz). This is because it supports 640x400 resolution on the M24, which was a proprietary mode introduced in that system.

EGA cards that support this proprietary signal type have a jumper for 25KHz mode. I believe the sync was also inverted or something. I can dig up some more info on that if you want.

I believe the Olivetti M240 (as opposed to the M24) also has a proprietary monitor with 640x400 support, but one that is downwards compatible with EGA at the software level. In contrast, the M24 only has CGA compatibility in addition to its proprietary 640x400 2-color mode.

You can find more about Olivetti monitors and their weird mode elsewhere in this forum.

mogwaay wrote on 2021-09-14, 15:50:

Hi MMaximus, sorry to comment on an old thread, but I'm building my own 8088 (V20) based PC and I've got a PEGA2A based EGA card […]
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Hi MMaximus, sorry to comment on an old thread, but I'm building my own 8088 (V20) based PC and I've got a PEGA2A based EGA card which works great at the normal 4.77MHz, but has post issues at 13.33 MHz Turbo mode I'm trying to implement. On your fast PCs, do you know what the ISA speed is on those motherboards?

I've got 24 and 30 MHz crystals coming to test at 8 and 10MHz Turbo also, I'm crossing my fingers that one of those will work. I'm a little confused by it as I have tried at 4 Wait States for IO requests but it can't keep up - might be the Video Memory reads/writes that are causing me trouble as they are not IO requests at are operating at 0WS at the moment (except for BUS_READY signals from the card which slow it down).

Cheers,
Chris!

Hey - no worries about bumping an old thread. I don't remember having changed any setting in the BIOS for the ISA bus speed so I assume it's the standard 8Mhz. I haven't tried but I suppose these old EGA cards might have trouble operating in an overclocked bus.

What kind of motherboard are you using? I wasn't aware you could fiddle with wait states on an XT board. I guess this is done via jumper settings?

Hi MMaximus! Thanks for getting back to me. My motherboard is a homemade PCB, based on the Xi8088. I have a simple Wait state generator, but it's only for IO R/W and a minimum IORDY wait states and I've not implemented any memory wait states and I'm pretty sure that's my problem.

Today I got my 24 and 30MHz osc for running the CPU at 8 and 10MHz and the EGA Card seems v stable at 8 which is cool, and is v unstable at 10MHz, loads of funny glitches, random characters being inserted as the screen scolls. So it makes sense that you say prob 8MHz, these cards seem stable there, 10 is a bit too much and 13.3 far too much! I'm hopeful if I introduce mem wait states I can push it further but I'll need to figure out a good way to do that (for PCB V2!).

Thanks again for your info, really helpful to have another experience of these old machines!