Electron games that require more than 32k

[rvounik]

I am having a hard time figuring out the reason for upgrading my Electron's memory to 64kb, like the ElkSD64 offers, for example. I cannot find any information on games that require 64k of memory.

Is there a list of games that require it? Or just a few examples would already be helpful.

And are there games that use multi-load, like on the c64?

[davidb]

There are quite a few games that use multi-load. Basically, all the multi-event sports games (e.g. Winter Olympics), many multi-stage arcade adventures (e.g. The Last Ninja), and games with loadable levels (e.g. Repton 3).

It's mostly application software that uses sideways RAM. I'm not sure if there were any games that could take advantage of it. I think that Repton: The Lost Realms can use it but can't check at the moment. No doubt someone can correct me on that.

[SteveF]

It's probably true that most games won't need more than 32K, but some games will like PAGE at &E00 - particularly anything which is a multi-load or where you can save/load your position during the game. If I remember correctly, 16K of the ElkSD64 memory is used to give you MMFS (for SD card access) without raising PAGE above &E00. There's a Chinnyvision video which discusses this, if you're interested.

If you happen to like text adventures, Ozmoo (there's a link back to stardot from that page if you want to read more) will let you play Z-code games on your Electron, but you need at least 48K of RAM in practice and the more memory the better.

[Kecske Bak]

Yes, there's an enhanced version of Repton The Lost Realms (ADFS disc version) that can use the extra memory so you get the BBC Micro graphics. It's quite incredible and I really don't know how Sarah managed it.

[ChrisB]

I think that in he limited market at the time targetting non-standard configurations probably just reduced available market too much so there wasn't much that required it. And when you're tape based multi-load isn't the best experience. I did convert my Untitled Dungeon Game to the Electron here : viewtopic.php?p=329674#p329674 which requires a DFS style filing system and Sideways RAM.

[rvounik]

Alright thanks a lot guys. So the reason the ElkSD64 offers extra memory is because the way the device works and its addressing gets in the way of how certain games load. So.. if I would stick with a good old tape recorder or even something like PlayUEF I will not be missing out on anything, it will just be a very slow experience?

The reason I'm asking all this is because my Electron did not come with a tape recorder but I do like to experience a few of the games. I'm just considering my options.

[paulb]

Alright thanks a lot guys. So the reason the ElkSD64 offers extra memory is because the way the device works and its addressing gets in the way of how certain games load. So.. if I would stick with a good old tape recorder or even something like PlayUEF I will not be missing out on anything, it will just be a very slow experience?

Having seen the ElkSD128 presented in a YouTube video recently, the way that it announces 128K on start-up (or 64K for the ElkSD64, I imagine) could be confusing to those not familiar with what kind of memory this is. On the Electron and Beeb, this extra memory is sideways memory that can be paged in at a certain location, but it isn't generally available for things like BASIC, largely because such memory sits in the same area as BASIC in the memory map.

Back in the day, when people bought ROM and RAM boards, they typically populated them with ROMs for things like languages, applications and utilities, and the RAM appears to have largely been used to install ROM images. If you have a certain number of ROM/RAM slots and a greater number of images, having sideways RAM gives you some flexibility about which "ROMs" you could have to hand. People may also have used such RAM for extra temporary workspace, for RAM disks, and so on.

Given that games were also supplied on ROM cartridge, people could have put images of those in sideways RAM instead, but I would imagine that such users would have been loading their images from disk and would probably have had disk versions of those games already. Such games wouldn't actually use the sideways RAM themselves, though: the way that they are delivered means that the RAM (or ROM in the original cartridges) is just a storage medium, they get loaded from that medium into the main RAM, and then they run from there. The benefits of putting such game images in sideways RAM are minimal.

At some point, people started to use sideways RAM a bit more creatively. Solidisk suggested "mega games" for the Electron in their advertising for their disk system which had 16K of sideways RAM, hinting that games could use that extra space and also potentially take advantage of some performance enhancements associated with running code in that part of memory, although none of these games were produced, apparently. I remember it being claimed somewhere that the RAM on those boards wasn't reliable.

A more practical but more exotic use of sideways memory occurred with disk systems like the Slogger Pegasus 400 where the DFS ROM could trade some of its memory space for a window into some extra RAM, with a limited amount of that RAM provided on the cartridge. This permitted the disk system to set PAGE to &E00 and therefore reduce incompatibility with tape-based software that relied on having as much memory available as possible.

When the Master series came out with some of the extra memory also supplied in the form of sideways RAM, there was more of an inclination for games authors to make use of it, so games like Exile and Stryker's Run were able to introduce some enhancements because of the extra memory. As previously noted, such assumptions about the customer base couldn't really be made for Electron users.

As for whether games could have been made that used extra RAM, Acorn's own cartridge-based games certainly did not take full advantage of that medium. There is nothing to stop a game being provided as an application (or "language" in Acorn's terminology), being instantly available, and running directly out of ROM: davidb's Jungle Journey and Castle Raider are both available in that form, I think. Games cartridges could have provided 32K of memory - some ROM and maybe some RAM - in the simplest scheme. More complicated cartridges can employ more ROM and RAM by having their own paging mechanisms, which leads us in the direction of things like the Mega Games Cartridge.

[Ramtop]

Alright thanks a lot guys. So the reason the ElkSD64 offers extra memory is because the way the device works and its addressing gets in the way of how certain games load.

The reason for the sideways memory banks on the ElkSD64 is basically cost; it was actually cheaper to put them in than do a design that didn't have them!

MMFS needs about 2.5K of memory as workspace, locating that in main memory raises PAGE and caused issues with games that were originally released on tape. You really need to put it in sideways space for best compatibility, so there has to be additional RAM of some kind fitted. The original plan for the ElkSD64 design was to implement a split sideways bank, with the lower 13.5K being ROM to hold MMFS and the upper 2.5K mapped as RAM. This bank could only be used for MMFS and nothing else. I used this approach on the ElkSD-Plus1 and it works very well.

But the logic required to do the split bank is more complex than the simple little CPLD chip on the ElkSD64 could handle, it could just barely cope with providing straightforward ROM and RAM banks. Plus, it turns out the cheapest SRAM chip that's widely available is 32K in capacity, so if the RAM is there why not make it available for use?

Having seen the ElkSD128 presented in a YouTube video recently, the way that it announces 128K on start-up (or 64K for the ElkSD64, I imagine) could be confusing to those not familiar with what kind of memory this is.

I regard this is a bit of a no-win situation. If the extra memory isn't announced people will assume their ElkSD is broken and complain. As it is I've had to explain many times why the ElkSD128 announces 144K at startup, not 128K or 160K. There's no way to make everyone happy, alas

[1024MAK]

Just to expand a little on what Paul has written…

As you may (or may not) know, the BBC B and Electron machines, as supplied have the entire address space (64K bytes) available for a 6502 microprocessor already full.

Half is the 32K bytes of RAM. The remaining areas are 16K used for BASIC, almost 16K bytes of OS (operating system) ROM and the small amount of space used or reserved for I/O (input/output) devices (not including screen memory).

Hence, there is nowhere to add any extra RAM unless some other area is “switched out”. With the BBC microcomputer range and the Electron, the system that is used is called sideways ROMs. The design allows BASIC to be “switched out” and another 16K ROM (or indeed 16K of RAM, or any mix of ROM and RAM) to be “switched in”.

While on the BBC B, sockets for sideways ROMs are standard, on the Electron it has to be done with an expansion.

While the sideways paging / banking memory system was originally only designed for use with ROM chips (BBC B) / ROM cartridges (Electron), it was soon found that RAM could be used as well.

Hence nearly all RAM extensions or expansions for the BBC microcomputer range and the Electron use the sideways system to add some additional RAM. As it’s possible to have multiple banks of 16K bytes blocks of memory, a higher capacity RAM chip can offer multiple lots of 16K bytes. Hence if a 32K RAM chip is used, you have a machine with a total if 64K bytes of RAM (32K built in as manufactured plus 2 lots of 16K of sideways RAM).

Just to confuse matters, there also exists other (more complex) ways to add more RAM. For example, “shadow” RAM. This allows the built in RAM to be used for the screen display, while the extra RAM is used for programs or data.

With any additional RAM, for commercial software to make use of it, the software had to be written to use it. As Paul says, as the vast majority of owners only had a standard machine, most games ignore any extra memory.

For the same reasons, this problem exists on other rival home computer systems.

Mark

[ElectronTubs]

I find it interesting the ways different 8bit computers manage the "more than 64k" of address space.

So the spectrum 48k, is non expandable (and I don't think there is any software way to do anything with the ROM) - it has 16k ROM, 48k RAM (with a 16k bank shared/contended with the screen/ula). The 128K has 16k ROM that can be switched out, so that it can run the 48k ROM or the 128k ROM. The last 16k can be "bank switched" with any of the other RAM, including the screen (allowing double buffering). The +2A/+3 adds in 4 different 16k ROMS - 48k, 128k, Disk OS and CP/M, but also introduces some modes where all 64k is available as RAM, but no ROM/other RAM.

The c64 does "shadow" RAM - the RAM is "behind" the ROM addresses (and can be poked, but not peeked, as the ROM is returned). Some trickery is done to get it to access more than 64k, with RAM paging and in-between screen refreshes, but haven't really looked into that.

I understand that the Commander X16 ( a new 8 bit computer) basically has one 16k bank that is paged for all of the other RAM. You might have 512MB, but you'll only every be able to see one 16k bank at a time ... .

[DutchAcorn]

... So the spectrum 48k, is non expandable (and I don't think there is any software way to do anything with the ROM) - it has 16k ROM, 48k RAM (with a 16k bank shared/contended with the screen/ula)....

Bit off-topic for this forum but there was at least one way of expanding the ZX Spectrum 48K to 64K using an extension supplied as a part of the "Shadow of the Unicorn" game.

Edit: I now understand the expansion actually supplied a custom 16K ROM, not RAM.

[1024MAK]

ZX Spectrum memory. Off topic indeed.

The normal way used by external interfaces/expansions was to use the built-in control line(s) to deselect the ROM(s) and then either page in extra ROM or extra RAM.

Or to modify the board so that the upper (expansion) RAM chips could be 64K DRAM chips and some extra control circuitry, and hence the top 32K bytes of the Z80 memory map could be paged between two different 32K banks.

And lastly, a 16K ZX Spectrum could have an external interface/expansion that could page whatever you liked from whatever memory you wanted in the upper half of the Z80 memory map. But these are user designed expansions, not commercial units.

The reality is that not many home computers were designed to take more than 64K bytes of memory. Most had no architecture designed for paged or banked RAM. Not until later in the 1980s anyway. The BBC B and the Commodore 64 are the only two from the beginning of the 1980s that were designed with paged or banked memory in mind.

Later, the Memotech MTX range and the Amstrad CPC range added to machines that had paged or bank switching. Then bank switching was added with the development of the ZX Spectrum 128 (Spanish model came first).

Mark

[ElectronTubs]

Yes, sorry didn't mean to take it so widely off topic ... well it is about memory.

Ooops, yes I'd forgotten about the Spectrum Cartridges, that were 16k, but I'm not sure if on the 48k you could then

So, In theory with an Electron for example, you could create a ROM, with 16k of game data. Then load from disk/tape another 32k (minus screen storage)? Eg giving you maybe 48k of memory to play with?

Would probably have been too expensive at the time ...

[jms2]

Yes, you could do that. One game on the BBC (Dr Who and the Mines of Terror) takes this approach.

As you thought, this was a prohibitively expensive option in practice, even on the BBC. For the Electron, things would have been worse as the machine doesn't have any rom slots as such, so the user would have had to buy a Plus 1 interface and a cartridge to put the rom in. That said, I guess it's no worse than the Acorn cartridge-based games. I wonder how profitable those were (or otherwise).

[1024MAK]

Cartridge-based games were only worthwhile if they could be sold in the thousands, no matter which machine or system was the target.

But to get the price down, you are talking a whole lot more having to be shifted.

Mark

[davidb]

That said, I guess it's no worse than the Acorn cartridge-based games. I wonder how profitable those were (or otherwise).

I wonder about that. Many of them only needed 16K ROMs but Starship Command needed 32K. In theory, serial ROMs could have been used, though maybe it would have required extra logic that offset any savings made by using them instead of regular ROMs.

[rvounik]

Thanks again guys, some great explanations. it is quite like the c64 then in terms of how much memory is available standard. And any extra memory is used in the same way memory expanders for the c64 worked. But most importantly, there is no direct need for me to upgrade my Electron memory.

I will probably have more questions later, both my A3010 and Electron are in need of attention