Lo-tech Memory Board FAQ
What do they do?
ISA ROM Board
The ISA-ROM-Board provides 32KB or 64KB or in-system re-programmable ROM. It can be used:
- for option ROMs, for example when developing option ROM code or to provide option ROM code to enable booting from a particular peripheral without it's own option ROM socket; or
- to provide the system ROM, for example to enable updated or patched system ROM code without the need to acquire a seperate UV ROM eraser and external programmer.
The board uses a AMIC 29F010A or SST39SF010 flash chip, which can be re-programmed at least 1,000 times.
1MB RAM Board
The 1MB-RAM-Board provides from 64KB to 940KB of system RAM to PC/XT class machines via a standard 8-bit ISA slot, enabling systems with between 16KB and 576KB of RAM to be expanded to 640KB. In system configurations where full 64KB pages are available between 640KB and 940KB ('high memory') the board can be used to populate these areas, which can then be used for certain purposes in DOS such as print spoolers.
2MB EMS Board
EMS is a memory expansion standard developed by Lotus, Intel and Microsoft to work around the 1MB physical address limit of PC/XT hardware (and its derivatives when used with MS-DOS). EMS works by presenting a larger address space (2MB in the case of the 2MB-EMS-Board) through a small window (known as the 'page frame') in the first 1MB of the PC's address space:
The physical memory on the EMS board that is visible through the page frame is controlled by updating registers on the card.
What don't they do?
- The 1MB RAM board can't expand the PC/XT system memory beyond the 1MB high water mark, because the 8088, 8086 and V20 CPUs only have 20 physical address lines.
- The 2MB EMS board can't be used in multiples to create 4MB, 6MB or more EMS
- The 1MB-RAM-Board doesn't need any device drivers, since the system BIOS will automatically detect the RAM (up to 640KB)
- The 2MB-EMS-Board requires:
For the RAM Boards, is a certain amount of memory needed in the system?
No, the use of the boards does not depend on having a certain amount of memory installed.