Est. 1984

This compact upgrade provides your BBC Model B with eight banks of 'sideways ROM'. Each bank is, of course, 16kB in length and is in the form of flash memory. This can be quickly and easily reprogrammed with ROM images using the supplied software. Sideways RAM is easily added in the spare sockets.

Free UK postage

Q & A

Which machines will it fit? It is suitable for the BBC Micro Model A and B only. The B+, Master 128 and Master Compact are not suitable. The memory board occupies the two sockets in the front right hand corner of the motherboard.

There are no links to configure as such. 99.9% of the time the links on the board will never need to be altered but they are there in the rare cases they are needed.

How many ROM images can be loaded into it? A maximum of eight in the upgrade board, although you still have the two sockets to the left available for normal use. The Beeb sees the memory board socket numbers as 2, 3, 6, 7, 10, 11, 14 and 15. You can also implement sideways RAM very easily in either or both of the spare sockets - see below.

Is any soldering required? No. The upgrade plugs into the two rightmost sockets on the main board and the supplied wiring loom clips onto three IC pins near the System 6522 VIA.

ROM expansion boards for the Model B tend to be a trade-off. An upgrade such as this, occupying only the standard ROM sockets, invariably has to use a few leads to pick up signals from other parts of the board. If you prefer, my other listings include a solderless ROM/RAM board which provides not only eight banks of flash memory but also eight banks of battery backed sideways RAM. Battery life is around five years from an inexpensive CR1225 lithium coin cell. Contact me for availability if it's out of stock.

What is a 'ROM Image (or ROM Dump)'? It's just an exact byte for byte copy of a normal EPROM and is often stored as a file on floppy disk or a modern solid state storage device. The original EPROM is usually 16kB long (16,384 or hex 4000 bytes). Multiple ROM images can be stored on disks or an SD card and programmed into the flash memory as needed. Clearly, there is no need to physically remove or insert EPROMs. ROM images are loaded into the flash ROM (or deleted) as and when required with easy keyboard commands.

How long does reprogramming take? A single 16kB ROM image is programmed into the flash memory and then verified in a couple of seconds. Clearly, the speed of the filing system plays a part, floppies being inherently slower than modern alternatives.

How is the programming software supplied? It's supplied on the flash memory chip. After installation, typing *ROM followed by *CAT brings up a list of files, one of which can be used to copy those files to your normal storage device (floppy, MicroSD, MMC etc). It's a very straightforward process.

What is sideways RAM? The flash memory on this board (SST39SF010) retains its data when power is turned off. Obviously this is normally a very useful property. However, unlike ordinary RAM, the 6502 processor cannot use flash ROM as a fast, temporary store. This is because the bytes that are written to the flash ROM take several microseconds to be stored. A RAM chip, on the other hand, accepts data immediately. Sideways RAM is particularly useful for loading 'E00' versions of filing system software. These are special versions of filing systems which are specifically written to operate in sideways RAM. In this way they do not need to claim any of the machine's normal memory for workspace and they use part of the sideways RAM instead. This in turn frees up extra memory in the computer and can help with compatibility with certain games.

Does it work with User Port MMC systems, ordinary floppy drives, Datacentre, Goteks and BeebSCSI? Yes. The upgrade is basically a means of installing 'sideways ROMs' without physically having to open the machine and fiddle about inside. The filing system is almost completely irrelevant. However, a machine which only has slow cassette tape storage is not suitable.

The ease of programming the flash memory means that is simple to try out different filing systems for the same piece of hardware. For example with a Gotek connected, you could easily experiment with various filing systems from Acorn (eg DFS and ADFS) and other third parties.

Can I add Sideways RAM later? Yes. This board has been designed so that you can add 32kB of sideways RAM (that is, two banks of 16kB) for minimal cost. All you need is a 32kB static RAM chip. Photo A shows a typical 32kB RAM chip (yellow dot) and this needs to be connected to the flash ROM board with two pieces of wire. Suitable wire and a connector are included but you will need to make a couple of soldered connections to the RAM chip. With the arrangement shown, you will have 16kB of RAM in socket numbers 8 and 12.

You could also add a further 32kB RAM chip in a similar way in place of the ROM with the red dot. That would give your machine eight banks of non-volatile flash memory and four banks of sideways RAM.

A suitable 32kB RAM chip is not included. They are readily available or I can supply one if needed. Please ask for details.

I've modified the motherboard on the underside to accept larger EPROMs (eg 27256 and 27512). Can this upgrade still be used? Yes. Modifying the motherboard in this way makes no difference. However, any existing ROM expansion board would need to be removed.

Can it be used on a machine with only a cassette tape for storage? No. The memory board itself will work, but in order to reprogram it you must have a reasonably fast filing system installed. The cassette filing system is too slow and restrictive. Ordinary floppies are fine (DFS and ADFS) as are any of the modern solid state storage systems (MMC, Micro SD, DataCentre, BeebSCSI, GoSDC etc).

Money-back guarantee

The product is covered by a 1 year guarantee. Additionally, most eBay Buy It Now sales are covered by what used to be called the Distance Selling Regulations (DSR). In essence this gives you a time period in which to return the goods for any reason whatsoever. If you wish to return this item within a 30-day period then you will receive a full refund (cost of the item itself and the postage too). The cost of returning the item to us is to be borne by the purchaser unless, of course, the item is actually faulty in which case we will refund any reasonable postage costs as well.