Why not use the PCI 486 motherboard as it is? It will have ISA sockets.

I must admit to being utterly confused your thinking process here.

Point 1: Sure, anything can be made.

Point 2: This would be the extremely hard part, knowing HOW to do it...right?

Point 3: Any more crazy questions?

canthearu wrote:

Why not use the PCI 486 motherboard as it is? It will have ISA sockets.
I must admit to being utterly confused your thinking process here.

For the sake of modifying an old favorite ISA only 486 and enjoying it run on PCI! 😎 😁

meljor wrote:

Point 1: Sure, anything can be made.

Great! But, can it be made via DIY at home with home stuff?

meljor wrote:

Point 2: This would be the extremely hard part, knowing HOW to do it...right?

Hence my question...

meljor wrote:

Point 3: Any more crazy questions?

Sure! There you go: (yes it's mine)
https://www.linkedin.com/pulse/more-questions … cola-di-pietro/

Thanks!

I'll make it simple

Its not really possible, you would need to change the chipset, you would need a new BIOS and a new board. It would turn out to be the same as the donor board you took the PCI chipset from, rather than your favorite ISA only 486.

https://www.youtube.com/watch?v=LPW70q4w5pw

canthearu wrote:

I'll make it simple

Its not really possible, you would need to change the chipset, you would need a new BIOS and a new board. It would turn out to be the same as the donor board you took the PCI chipset from, rather than your favorite ISA only 486.

I see, that's sad! It would defy the whole purpose of having THAT particular ISA only 486 run with added working PCI too, too bad!

Unless... can't a motherboard have 2 chipsets and 2 bioses, like an extension? (LOL)

Errius wrote:

https://www.youtube.com/watch?v=LPW70q4w5pw

omgosh!

Its not possible due to signal integrity issues surrounding soldering a spiderweb of wires in the air. On the other hand its totally possible to build VLB card with PCI bridge, or CPU interposer with PCI bridge 😮)

Some basics in reverse order (from difficult down to bed reading material), you should be able to get pdfs or rent:
'High Speed Digital Design: A Handbook of Black Magic' by Howard Johnson. Highly approachable video featuring two absolute legends: https://www.youtube.com/watch?v=e0Uv5Zd9wXM
http://alternatezone.com/electronics/pcbdesign.htm
Digital Design with an Introduction to the Verilog HDL by M. Morris Mano - logic basics
The Art of Electronics by Paul Horowitz and Winfield Hill - absolute bible, expensive so rent
Microprocessor Theory and Applications with 68000/68020 and Pentium by M. RAFIQUZZAMAN - quite readable cpu interfacing basics
Invitation to Computer Science by G.Michael Schneider - another light read
Logic & Computer Design Fundamentals by M. Morris Mano - very easy to read
Upgrading and Repairing PCs (somewhere around 10th Edition) by Scott Mueller https://archive.org/details/URP_8th_edition

Learn this and we can talk some more 😀

canthearu wrote:

I must admit to being utterly confused your thinking process here.

hunger for knowledge? I admire his enthusiasm, reminds me of spending whole summer trying to mod old one channel CB radio instead of working ~7 days to earn for brand new one 😀

What about making a PCB you clip on the chipset (kinda like they do with Amiga 600) and then let the user have working vlb (as far as I know, VLB is just the bus sitting inbetween the CPU and the chipset/ram, right ?)

Just no.

The chipsets have very different pinouts. You can design and order your own DIY PCB and install all components there, but it's complicated and very much time consuming.

It may be possible to add VLB bus off the 486 cpu socket, the same way you can add a passive ISA backplane off the right cpu pins on an 8088.

Trouble is you would need a cable like the 80pin ide cable that could work around all the noise issues and god knows the shape and ground plane issues that would occur at the socket

rasz_pl wrote:

Its not possible due to signal integrity issues surrounding soldering a spiderweb of wires in the air. On the other hand its tot […]
Show full quote

Its not possible due to signal integrity issues surrounding soldering a spiderweb of wires in the air. On the other hand its totally possible to build VLB card with PCI bridge, or CPU interposer with PCI bridge 😮)

Some basics in reverse order (from difficult down to bed reading material), you should be able to get pdfs or rent:
'High Speed Digital Design: A Handbook of Black Magic' by Howard Johnson. Highly approachable video featuring two absolute legends: https://www.youtube.com/watch?v=e0Uv5Zd9wXM
http://alternatezone.com/electronics/pcbdesign.htm
Digital Design with an Introduction to the Verilog HDL by M. Morris Mano - logic basics
The Art of Electronics by Paul Horowitz and Winfield Hill - absolute bible, expensive so rent
Microprocessor Theory and Applications with 68000/68020 and Pentium by M. RAFIQUZZAMAN - quite readable cpu interfacing basics
Invitation to Computer Science by G.Michael Schneider - another light read
Logic & Computer Design Fundamentals by M. Morris Mano - very easy to read
Upgrading and Repairing PCs (somewhere around 10th Edition) by Scott Mueller https://archive.org/details/URP_8th_edition

Learn this and we can talk some more 😀

canthearu wrote:

I must admit to being utterly confused your thinking process here.

hunger for knowledge? I admire his enthusiasm, reminds me of spending whole summer trying to mod old one channel CB radio instead of working ~7 days to earn for brand new one 😀

Wow man!!! THANK YOU SOOO MUCH!!!!! Who are you?? 🤣

rmay635703 wrote:

It may be possible to add VLB bus off the 486 cpu socket, the same way you can add a passive ISA backplane off the right cpu pins on an 8088.
Trouble is you would need a cable like the 80pin ide cable that could work around all the noise issues and god knows the shape and ground plane issues that would occur at the socket

ph4nt0m wrote:

Just no.
The chipsets have very different pinouts. You can design and order your own DIY PCB and install all components there, but it's complicated and very much time consuming.

Thanks guys, it seems more and more doable...

I recently stumbled onto this IBM riser card http://ps-2.kev009.com/pcpartnerinfo/ctstips/c892.htm
goes into this 486 VESA motherboard http://ps-2.kev009.com/pcpartnerinfo/ctstips/a5a2.htm http://ps-2.kev009.com/eprmhtml/eprm/f347.htm
and converts VESA bus to PCI 😀 Seems IBM was the only vendor to implement optional PCI bridge, they called it SelectaBus.
http://www.members.aon.at/mcabase/mcb/tli/rc_PC137x.htm
fru 88G4255, 88G4265
Sadly it as only used in few models manufactured for a ~year, so its pretty much unobtanium, otherwise it could be a great candidate for modding

Wow, I can't even imagine the compatibility nightmare of a VLB to PCI bridge. Yikes! 🤣

wow, nightmares apart indeed, that's a very interesting and juicy piece of hardware! Thanks rasz_pl !

Ozzuneoj wrote:

Wow, I can't even imagine the compatibility nightmare of a VLB to PCI bridge. Yikes! 🤣

VESA/LocalBus/VLB is just a fancy brand name for providing hardware access to CPUs 32bit data bus, IBM just made PCI bridge an optional add-on while later designs incorporated it on board, electrically makes no difference.

Ozzuneoj wrote:

Wow, I can't even imagine the compatibility nightmare of a VLB to PCI bridge. Yikes! 🤣

VLB is a direct extension of the 32-bit system bus. It may be implemented on 16-bit and 64-bit system buses, too, with a buffering logic. There is no VLB to PCI bridge because it doesn't make sense. A host to PCI bridge is needed. Could be a custom ASIC or FPGA.

Well it have been implemented on 16-bit platforms : I've seen a Ti486SXLC2 motherboard with a VLB connector once here, so that have been made. It also have been made for pentiums, but here I think they've just turned all the memory busses into 32-bit busses as the chipset on these usually work with only one 72 pin RAM stick and have terrible memory performance.

Lets get real ambitious and blend some MCA slots in there as well.