sergey
Veteran Member
Hi,
I have all PCBs mentioned above. See http://n8vem-sbc.pbworks.com/w/page/35044530/PCB%20Inventory (Xi 8088 project near the bottom of the page) for current inventory.
Please PM me if you like to purchase them...
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Sergey's XT Project - Home-made IBM PC compatible system
- Thread starter sergey
- Start date
Hi,
I have all PCBs mentioned above. See http://n8vem-sbc.pbworks.com/w/page/35044530/PCB%20Inventory (Xi 8088 project near the bottom of the page) for current inventory.
Please PM me if you like to purchase them...
chjmartin2
Experienced Member
- Joined
- Dec 26, 2012
- Messages
- 435
Hi,
Can I buy everything I need from you to build one of these? I have a Vendex Headstart Plus case that could use a system inside it. I want an NEV V20HL in the worst way. (Why does it max out at 13MHz by the way? I thought that the best possible was 16 MHz?)
Chris
Scali
Veteran Member
One question I have is: how compatible is this system with a real IBM PC?
I have been exploring democoding on 8088-4.77 with CGA, and found the following with CGADEMO: http://scalibq.wordpress.com/2014/11/22/cgademo-by-codeblasters/
Apparently my Philips is slightly slower at 4.77 MHz than a real IBM. The working theory is that the chipset has some extra buffers in order to make it run at 8 MHz (which would be async with some parts of the system, that have to remain at 4.77 MHz). This introduces some extra waitstates here and there.
We are looking at doing certain 'cycle-exact' effects, by reprogramming CGA registers on-the-fly, much like how special tricks on the VIC-II on C64 work for example.
I have found that some of these effects work on real IBM 5150, 5155 and 5160, but not on the Philips, because it is not EXACTLY the right speed. This will probably hold true for 99% of all clones out there.
I have been exploring democoding on 8088-4.77 with CGA, and found the following with CGADEMO: http://scalibq.wordpress.com/2014/11/22/cgademo-by-codeblasters/
Apparently my Philips is slightly slower at 4.77 MHz than a real IBM. The working theory is that the chipset has some extra buffers in order to make it run at 8 MHz (which would be async with some parts of the system, that have to remain at 4.77 MHz). This introduces some extra waitstates here and there.
We are looking at doing certain 'cycle-exact' effects, by reprogramming CGA registers on-the-fly, much like how special tricks on the VIC-II on C64 work for example.
I have found that some of these effects work on real IBM 5150, 5155 and 5160, but not on the Philips, because it is not EXACTLY the right speed. This will probably hold true for 99% of all clones out there.
bonedaddy
Member
I have Sergey's cards available now. Please see http://n8vem-sbc.pbworks.com/w/page/35044530/PCB Inventory (as Sergey said) for how to contact me or PM me here.
These are the bare boards, you'd need to source parts and build them yourself. Most are through hole parts though (big exceptions being the SVGA and XT-CF-Lite)
I also have the ISA-FDC and ISA-IDE boards.
Todd
These are the bare boards, you'd need to source parts and build them yourself. Most are through hole parts though (big exceptions being the SVGA and XT-CF-Lite)
I also have the ISA-FDC and ISA-IDE boards.
Todd
sergey
Veteran Member
It is related to the way V20 and V20HL are clocked. 8088 uses 33% duty cycle clock, while V20HL needs 50% duty cycle to achieve the maximal frequency. Xi 8088 uses 33% duty cycle clock (as produced by 8284 clock generator), which limits the CPU frequency to about 12 MHz (13.33 MHz was the fastest I could get it running).
Also other things will limit the frequency: board does have wait state generator for I/O, but not for memory. So the controllers that have some memory (e.g. video RAM, BIOS extension ROM) need to be fast enough or have a wait state logic, and insert wait states themselves.