We are about to do another run of our popular S-100 Bus Z80 CPU V2 board. This board can run in systems (with bus termination etc.) at up to 10MHz. Apart from all the then common features found on many older S100 Z80 boards (and being completely S-100 IEEE-696 compliant), it had an extremely clever and powerful ability to allow the Z80 to address up to 1 MG of RAM in 16K "windows" within the Z80's address space. This is described here:-
Its primary importance is that it can be used to address greater than 64K of RAM for CPM3 and that it can be used to load/examine 8086 code at the top of the 1MG address space.
The new “V2” version of the board now has the ability to (under software control) dynamically switch between two 4K blocks of code in its onboard 28C64 EEPROM (or EPROM) yet still only occupy 4K in the Z80’s 64K memory space. This in effect almost doubles the size of a possible Z80 monitor. The extra code (currently being written) will include things like directly downloading binary files from a PC into the Z80’s 64K (or 8086’s 1M) address space.
In addition, the S-100 Z80 CPU V2 has the ability to use an external CPU clock from an external source (S-100 bus pin 66 aka NDEF3). This is essential for CPU to video synchronization for MSX compatibility particularly in games. There will be a corresponding ability to export a CPU clock signal on the next version of the S-100 VDP board although this could come from any S-100 board.
Current owners of the V1 board can just switch the IC’s to this new bare board.
The S-100 Z80 CPU V2 PCBs will be $20 each as per the usual arrangement. Shipping in the US is $3 for a single PCB and $2 for each additional PCB. Shipping internationally is $12.75 for a single PCB and $3 for each additional PCB. This is for the bare basics USPS first class postage with no tracking or insurance. The builder assumes all risk of delivery as per usual arrangement.
My preference is to sell these PCBs to vintage computer/home brew computer/classic computer hobbyists first but if there are any remaining boards I will put them on eBay.
Please send a PayPal to LYN...@YAHOO.COM with the subject “S-100 Z80 CPU V2 board” and I will reserve your board(s). I need about 20 pre-orders to warrant a manufacturing run. I will post more information as it becomes available.
Thanks and have a nice day!
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