Microbee Core boards
Static RAM Core boards
Overview
- Early versions of the Static RAM Core board use banks of 2KB Static RAM (SRAM) chips to provide a total of 8KB, 16KB, 32KB or 56KB program memory for the machine. Later versions added support for 8KB SRAM chips.
- SRAM Core boards can be fitted with a battery (4-5 volts) that allows the RAM contents to be preserved while the machine is powered off. Early versions used a non-rechargable battery for this, but later versions changed to a rechargable NiCd battery.
- Starting with support for 4KB EPROMs, later versions added support for 8KB and 16KB EPROMs as well as 8KB Mask ROMs.
- All SRAM Core boards have provision for a 50 way Expansion Interface at the rear, though most do not have the associated connector fitted as standard.
Board Number | Component Side Image | Solder Side Image |
|
1632 REV D |
| ||
MB1732 |
| ||
MB1732-33 |
| ||
MB1656 |
| ||
MB8328-2 |
| ||
MB8328-4 |
| ||
MB8328-6 |
| ||
MB8328-4 Premium MB8328-6 Premium |
|
Configuration Details
Core board MB8328-x
These are the final Static RAM Core boards to be produced. They were designed as a universal memory board to suit a range of Microbee models with differing capabilities and configurations. A variety of RAM and ROM IC types and configurations are supported and some non-intuitive programming techniques are required to control the various features of this board. The table below provides more specific detail on these boards and how to operate them.
IC |
Function |
Memory Map |
MB8328-2 |
MB8328-4 |
MB8328-6 |
|
IC1, IC2 and IC6, IC11, IC16, IC7, IC12, IC17 | RAM | 0000h - 3FFFh |
2KB 6116 SRAM or 8KB 6264 SRAM | as per MB8328-2 | as per MB8328-2 |
|
IC3, IC4 and IC8, IC13, IC18, IC9, IC14, IC19 | RAM | 4000h - 7FFFh |
2KB 6116 SRAM or 8KB 6264 SRAM | as per MB8328-2 | as per MB8328-2 |
|
IC5 | Basic A ROM | 8000h - 9FFFh | 8KB Mask ROM or 8KB 2764 EPROM | as per MB8328-2 when used with Standard models. Also supports a 16KB 27128 EPROM (as 2x 8KB banks) when modified for the Premium PC85 | as per MB8328-4 |
|
IC10 | Basic B ROM | A000h - BFFFh | 8KB Mask ROM or 8KB 2764 EPROM or 8KB 6264 SRAM | as per MB8328-2 | as per MB8328-2 |
|
IC15 | PAK0/8 ROM | C000h - DFFFh | 8KB Mask ROM or 8KB 2764 EPROM | as per MB8328-2 | as per MB8328-2 |
|
IC20 | NET ROM | E000h - EFFFh | 4KB 2732 EPROM or 8KB 2764 EPROM (as 2x 4KB banks) | as per MB8328-2 or 16KB 27128 EPROM (as 4x 4KB banks) | as per MB8328-4 |
|
IC25 | PAK1/9 ROM | C000h - DFFFh | 8KB 2764 EPROM | as per MB8328-2 or 16KB 27128 EPROM (as 2x 8KB banks) | as per MB8328-4 |
|
IC24 | PAK2/10 ROM | as per IC25 | as per IC25 | as per IC25 | as per IC25 |
as per IC25, except different PAK numbers are used to select this IC. |
IC23 | PAK3/11 ROM | as per IC25 | as per IC25 | as per IC25 | as per IC25 |
as per IC25, except different PAK numbers are used to select this IC. |
IC22 | PAK4/12 ROM | as per IC25 | as per IC25 | as per IC25 | as per IC25 |
as per IC25, except different PAK numbers are used to select this IC. |
IC27 | PAK5/13 ROM | as per IC25 | as per IC25 | as per IC25 | as per IC25 |
as per IC25, except different PAK numbers are used to select this IC. |
Dynamic RAM Core boards
Overview
- Microbee RAM was changed from SRAM to DRAM in later models.
- Banks of 8x 64Kb Dynamic RAM (DRAM) chips were used to provide either 64KB (1 bank) or 128KB (2 banks) total RAM capacity.
- DRAM Core boards also included an integrated floppy disk controller (FDC).
- The DRAM core boards use port 50H to manipulate the memory map. This determines whether the ROM is mapped into memory and also controls the video location.
Board Number | Component Side Image | Solder Side Image |
|
MB-168 8312-13 |
| ||
MB-168 8312-2 |
| ||
MB8342-2 |
| ||
MB8342-3 |
| ||
MB8342-4 |
|
Premium Plus+ Core boards
Overview
- Developed in 2012 by Microbee Technology especially for the limited edition Premium Plus+ release.
- Uses modern surface mount components to provide RAM, ROM and FDC capability for the Premium Plus+.
Board Number | Component Side Image | Solder Side Image |
|
21-01000-01 |
|