8086 MS DOS forum?

[Robb Bates]

A little off topic, but can anyone suggest a forum or message board for 8086 MS DOS machines?  Like bare bones, minimal homebrew kind of stuff?

I figured someone here may know of one.

Robb

[Sergey Kiselev]

It depends on what do you want to discuss.

Vintage Computing Federation forums have several IBM PC, PC/XT, PC/AT related subforums: https://forum.vcfed.org/index.php?categories/ibm-computers-pcs-clones-and-descendants.1230008/

Although they do discuss some homebrew stuff, the focus there is mostly on using existing commercial systems, perhaps with some homebrew extensions (e.g., XT-IDE).

There are also generic homebrew groups that among other things discuss 8086/8088 systems:

https://groups.google.com/u/1/g/retro-comp

https://www.retrobrewcomputers.org/forum/index.php

For my own projects I used a combination of all these above.

There are also VOGONS forums: https://www.vogons.org/

I had a thought of creating an x86 specific homebrew group/forum, but I don't know how much activity is happening with x86 specifically (homebrew people really seem to like the simplicity of Z80). Also there is a concern that some of the potential audience might be lost - both experienced people that perhaps not interested in x86 specifically, but still can share their experience, and beginners that haven't built anything with x86, but might be interested in that.

Regardless, what are you working on? Any particular questions you have?

[Andrew Lynch]

Hi

Considering the Z80 has gone out of production and availability is rapidly declining, I think the subject of hobbyist 8088/8086 takes on more urgency.

If Z80 CPUs become unobtainium, which is the next logical hobbyist processor?  6502?  8088/8086?  68K?

I am thinking 8088 is the obvious successor since they were manufactured in the millions to support the PC/XT and clones market.

Another possibility is microcontrollers masquerading as processors.

The real issue is the lack of something like ROMWBW for 8088/8086.  MS-DOS would be great but drives a lot of hardware decisions up front.

Merovingian: Choice is an illusion created between those with power and those without.

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[Sergey Kiselev]

 AM UTC-7 Andrew Lynch wrote:

Considering the Z80 has gone out of production and availability is rapidly declining, I think the subject of hobbyist 8088/8086 takes on more urgency.

I don't think we'll run out of Z80 any time soon. There seems to be ample supply for re-manufactured or NOS parts.

 

If Z80 CPUs become unobtainium, which is the next logical hobbyist processor?  6502?  8088/8086?  68K?

 

Unfortunately most of these are not being manufactured any more either.

Renesas (that bought Intersil, that bought Harris) announced discontinuation of the 80C88 earlier this summer.

65C02 is still being manufactured by WDC.

The supply of older 8088 seems to be running dry as well.

 

The real issue is the lack of something like ROMWBW for 8088/8086.  MS-DOS would be great but drives a lot of hardware decisions up front.

There are a few open source BIOSes for x86 - GLaBIOS, my 8088 BIOS, the BIOS used on SBC-188, etc. All can be modified to run on various hardware. 

The MS-DOS relies on just a few things, other than the x86 instruction set, such as some BIOS entry point addresses. John Coffman and I found these dependencies more than 10 years ago when working on SBC-188.

So hardware compatibility with IBM PC is not strictly required to run MS-DOS. The problems start once you'd try to run applications. Anything that bypasses MS-DOS or BIOS calls, which many MS-DOS applications do, especially to access display directly instead of using slow BIOS routines.

By the way, it would be an interesting experiment to try to find how does MS-DOS's IO.SYS work. While back, when MS-DOS was just released, the compatibility with IBM PC was not required, the idea was that hardware vendors would customize IO.SYS for their hardware, similarly to how hardware vendors would customize CP/M's BIOS.

--Sergey

[Andrew Lynch]

Hi Sergey

You probably have seen this already.  There is presently a lot of drama on the S-100 mailing list regarding availability of Z80 CPUs.  Apparently, the used part market (eBay, etc.) is well saturated with fakes and remarked chips.  This is not news, but it has led to some people buying multiple Z80s in batches and using part testers to sort out the NMOS vs. CMOS units and speed rate them, cull out the duds, etc.  

This is not a good sign in my opinion.  We've seen this sort of thing with other components (V9958s) where there is high demand and then a lot of fakes and remarked chips flood the marketplace.  I hope this is just a temporary phase, but it may signal the hobbyist Z80 CPU market is drying up.  The parts may still be available but prepare to pay big bucks for genuine articles.

All I am saying is the signs I see are disturbing, and it may be prudent to look at some alternatives.  I've experimented with microcontrollers with the idea they may be more durable considering they are so commonly used in appliances and consumer goods.  They may be more available for longer.

Regardless, have a great day!

Merovingian: Choice is an illusion created between those with power and those without.

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[Sergey Kiselev]

On Thursday, August 28, 2025 at 3:43:53 AM UTC-7 Andrew Lynch wrote:

You probably have seen this already.  There is presently a lot of drama on the S-100 mailing list regarding availability of Z80 CPUs.  Apparently, the used part market (eBay, etc.) is well saturated with fakes and remarked chips.  This is not news, but it has led to some people buying multiple Z80s in batches and using part testers to sort out the NMOS vs. CMOS units and speed rate them, cull out the duds, etc.  

I was not paying attention to that drama ;). Although it is not surprising. Even going back 15 years or so - ECB SBC and Zeta SBC times, there already were "refurbished" and relabeled Z80's and other chips. I recall 10% or so of FDC9266 controllers I got for Zeta kits were defective... And of course all were relabeled.

 

This is not a good sign in my opinion.  We've seen this sort of thing with other components (V9958s) where there is high demand and then a lot of fakes and remarked chips flood the marketplace.  I hope this is just a temporary phase, but it may signal the hobbyist Z80 CPU market is drying up.  The parts may still be available but prepare to pay big bucks for genuine articles.

Even a year ago, when new genuine Z84C00's were still available, many people preferred buying cheaper Chinese parts. I did see the V9938/V9958 complains... I guess Omega Home Computer and similar homebrew MSX systems are to blame for the high demand.

 

All I am saying is the signs I see are disturbing, and it may be prudent to look at some alternatives.  I've experimented with microcontrollers with the idea they may be more durable considering they are so commonly used in appliances and consumer goods.  They may be more available for longer.

There are multiple ways. And probably different people will feel differently about them.

- Z80 can be emulated by fairly cheap microcontrollers. Of course there is a question about availability of these microcontrollers now and in the future.

- eZ80 can be used, although it requires SMD soldering. But perhaps a breakout board would help.

- Full software emulation on RPi or similar... Using RunCPM for example.

Going back to the topic of 8088, DigiKey shows a large stock from Rochester Electronics.

They also show Z80 NMOS 6 MHz in PLCC package for quite a reasonable price: https://www.digikey.com/en/products/detail/zilog/Z0840006VSC/11520766

The only problem there is that they require bulk purchase. 

As far as I know, Rochester Electronics specializes on production of older parts. They would either buy unpackaged wafers and package them, or even masks, and make their own chips. 

 

[free...@gmail.com]

FWIW I've had very good luck buying chips from Aliexpress. seems the payment processor holds them to a higher standard, so the junk gets offloaded on eBay. 

Justin 

[free...@gmail.com]

the WDC65C02 is still in production. Personally I would like to see more people taking an interest in the 65C265. it's an integrated version of the 16 bit 65C816 that includes serial ports and address demuxing so it can directly address 16 megs of address space. 

Justin 

[Gary S]

Not sure if I asked this previously....
but what about the v20/30/40/etc series of chips ?
yeah i know they are only 8080 compatible, but they are also 8086 compatible as well.
not sure of their availability thou.

then eventully for z80 I forsee an fpga solution or something similar with plug in conversion boards...

[Greg Holdren]

Try http://forum.6502.org/ Just a quick search looks like there many hits.

Greg

[Greg Holdren]

You can check out forum<dot>6502<dot>org

It looks like there are some 65C265 discussions there.

Greg

[Greg Holdren]

There is a Discord sever called EMM Computers that Elijah M Miller has setup to discuss 8088/V20 and other NEC Vxx based boards concerning HW design/SW/BIOS etc. You can get the Discord link from his YT comments in his videos.

https://www.youtube.com/@elijahmmiller 

www.homebrew8088.com

Greg

On Friday, August 29, 2025 at 12:32:40 AM UTC-7 Gary S wrote: