POLL: How much Sideways RAM?

for bbc micro/electron hardware, peripherals & programming issues (NOT emulators!)
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How much Sideways RAM does your BBC Model B have?

None
2
6%
16K (1 bank)
4
11%
32K (2 banks)
8
23%
48K (3 banks)
1
3%
64K (4 banks)
8
23%
80K (5 banks)
0
No votes
96K (6 banks)
2
6%
112K (7 banks)
0
No votes
128K (8 banks)
8
23%
All the RAM in the world
2
6%
 
Total votes: 35

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kieranhj
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POLL: How much Sideways RAM?

Post by kieranhj » Sun Jan 13, 2019 2:04 pm

Folks,

Sydney's poll from a few years ago suggested that ~90% of people have Sideways RAM in their machines but I was wondering exactly how much, specifically for the BBC Model B. If you have multiple machines please either select the highest amount or the one that you use most often as your day-to-day machine, whichever you prefer.

The reason for asking is that it's very tempting to develop software solely for the Master to guarantee that 64K SWRAM is available (LK's 38/39 notwithstanding) but it is also nice to try and make sure as wide a range of people can experience games & demos, etc. on real hardware when possible. 16K extra can go a long way, 32K even more so!

Cheers,
Kieran
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1024MAK
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Re: POLL: How much Sideways RAM?

Post by 1024MAK » Sun Jan 13, 2019 2:45 pm

Err, depends on which BBC B...

I have this Ctorwy31 BBC 128K Sideways RAMfitted in the BBC B that I use most often. When I actually have batteries fitted and some ROMs loaded, it’s configured as having four of the 16k byte banks write protected, with no write protection on the remaining four 16k byte banks. So I have selected “64K (4 banks)”.

The amount varies with my other BBC B’s (from none to some). The intention is to modify one of my others as described by Mark H. in his BBC Model B DIY 32K Sideways RAM, for under a Fiver. As I have some suitable SRAM chips and have some spare 27512 EPROMs.

Mark
Last edited by 1024MAK on Sun Jan 13, 2019 2:47 pm, edited 1 time in total.

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Re: POLL: How much Sideways RAM?

Post by RobC » Sun Jan 13, 2019 2:50 pm

It might also be worth asking how many people have a Pi co-pro as this would be another option for porting games (e.g. by using the 1GHz native core or by using bank switching on the 6502 core). Either way, it's another way of getting lots of memory.

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Re: POLL: How much Sideways RAM?

Post by cmorley » Sun Jan 13, 2019 3:12 pm

Everyone needs some OSRAM :)

Execute code from one bank and use the other bank for data without aby bank switching 8) . Make the C64 jealous. Plus you can rewrite the 6502 vectors at FFFA, C, E

I could probably do a cost reduced (less fiddly to assemble) one or self assembly kit... all it is waiting for is a killer app :lol:
Last edited by cmorley on Sun Jan 13, 2019 3:12 pm, edited 1 time in total.

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Re: POLL: How much Sideways RAM?

Post by geraldholdsworth » Sun Jan 13, 2019 3:23 pm

I've got a Master - but I've put in another 64K of RAM using RAM chips in the cartridges. This means I have sideways RAM from slot 0 up to, and including, slot 7. That's without using either my Turbo internal co-pro or 6502 external co-pro.
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Re: POLL: How much Sideways RAM?

Post by sweh » Sun Jan 13, 2019 4:04 pm

My BITD B has a Solidisk 2M128 board (so 128K RAM, 128K ROM, with some not-quite-compatible shadow/buffer modes) . My second B has an IFEL board (so 128K RAM, 64K flash, 64K ROM). Both machines have a matchbox copro.
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Re: POLL: How much Sideways RAM?

Post by dv8 » Sun Jan 13, 2019 4:23 pm

I've got 128K (8 banks) in all my machines. One has an IFEL (ctorwy31) ROM/RAM board, the others are homebrew mods (64K ROM, 64K flash, 128K RAM).

I prefer to keep the number of permanently installed ROMs to a minimum and load images in as I need them.

BTW, if anyone is thinking of following the RetroClinic DIY mod, be aware that the connections to IC76 are the wrong way round for a 64K EPROM.

Pin 1 of a 27C512 is A15 and should connect to IC76 pin 11.
Pin 27 of a 27C512 is A14 and should connect to IC76 pin 12.

Pin 1 of a 62256 RAM is A14 and can be connected to either pin of IC76, giving two 16K slots that are either 4 banks apart (pin 12) or 8 banks apart (pin 11).

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Re: POLL: How much Sideways RAM?

Post by CMcDougall » Sun Jan 13, 2019 4:28 pm

my BITD watford electronics Rom/Ram board had the full 144k , 16k was battery backed up :D
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Re: POLL: How much Sideways RAM?

Post by kieranhj » Sun Jan 13, 2019 5:08 pm

cmorley wrote:
Sun Jan 13, 2019 3:12 pm
Everyone needs some OSRAM :)

Execute code from one bank and use the other bank for data without aby bank switching 8) . Make the C64 jealous. Plus you can rewrite the 6502 vectors at FFFA, C, E

I could probably do a cost reduced (less fiddly to assemble) one or self assembly kit... all it is waiting for is a killer app :lol:
OSRAM would make the Stunt Car Racer port almost trivial! Apart from sorting out ZP, splatting the vector table at $200 and overloaded RAM/IO between $D000-$DFFF it should 'just work' in MODE 4 at least (keyboard input notwithstanding.) :)
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Re: POLL: How much Sideways RAM?

Post by jgharston » Sun Jan 13, 2019 5:40 pm

My Beeb as an Aries B32 and one bank of sideways RAM, so depending on setup it has 16K, 28K, 32K, 42K or 48K of sideways RAM. :)

Code: Select all

$ bbcbasic
PDP11 BBC BASIC IV Version 0.25
(C) Copyright J.G.Harston 1989,2005-2015
>_

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Lardo Boffin
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Re: POLL: How much Sideways RAM?

Post by Lardo Boffin » Sun Jan 13, 2019 6:12 pm

cmorley wrote:
Sun Jan 13, 2019 3:12 pm
Everyone needs some OSRAM :)
So many types of RAM...

Is this the RAM that keeps Page at &E00 regardless of DFS etc.?

I currently only have single 16K banks of sideways RAM in each of my Model Bs (on original Watford boards etc.) but will be getting a modern version shortly with 64K of RAM.

It did use to have an IFEL RAM/ROM board but pretty much gave it away. This was before I could solder and the flying leads kept coming lose.

I have a pi co proc that gets plugged into whichever beeb I am using at the time.
BBC model B 32k issue 4, 16k sideways RAM, Watford 12 ROM board, Acorn 6502 coproc
BBC model B 32k issue 7, turboMMC, Opus Challenger 3 512k, Pi 3 coproc
USA Model B
BBC Master, Datacentre + HDD, pi co-proc, econet

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Re: POLL: How much Sideways RAM?

Post by Kazzie » Mon Jan 14, 2019 11:16 am

Lardo Boffin wrote:
Sun Jan 13, 2019 6:12 pm
cmorley wrote:
Sun Jan 13, 2019 3:12 pm
Everyone needs some OSRAM :)
So many types of RAM...

Is this the RAM that keeps Page at &E00 regardless of DFS etc.?
I had to look it up myself. It's shadow RAM hiding in the OS ROM's address space. See http://www.boobip.com/hardware/osram
BBC Model B 32k issue 7, Sidewise ROM board with 16K RAM
Archimedes 420/1 upgraded to 4MB RAM (mid- restoration)
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Re: POLL: How much Sideways RAM?

Post by cmorley » Mon Jan 14, 2019 11:25 am

Kazzie wrote:
Mon Jan 14, 2019 11:16 am
I had to look it up myself. It's shadow RAM hiding in the OS ROM's address space. See http://www.boobip.com/hardware/osram
Original forum thead here: viewtopic.php?f=3&t=13147&hilit=osram

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Re: POLL: How much Sideways RAM?

Post by tricky » Mon Jan 14, 2019 12:19 pm

Its great for basic and demos, but a bit chicken and egg for games.

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Re: POLL: How much Sideways RAM?

Post by kieranhj » Mon Jan 14, 2019 4:48 pm

So great to see everyone showing off about the size of their, err, RAM..! A much broader spread of values than I was expecting (I almost capped the poll at 64K - I'm glad I didn't.)

So a conclusion might be that if requiring 16K (1x bank) of SWRAM is going to cover ~90% of the (active) Beeb population (from Sydney's previous poll) then requiring 32K (2x banks) is going to cover ~90% of that, so very roughly ~80% of the total.

I think these are helpful numbers for us to work with, particularly when thinking about converting content or code from other 8-bit platforms that have 48K, 64K or 128K RAM as standard.

For Stunt Car Racer specifically I think the technical difficulty of moving the data that currently exists from HAZEL into a 3rd SWRAM bank will be the determining factor. It would be nice to enable lucky Model B users with 48K extra RAM to play the game, even if Master is the 'lead' platform, but not if it's going to be weeks of extra work.
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Re: POLL: How much Sideways RAM?

Post by sweh » Mon Jan 14, 2019 4:57 pm

One "gotcha" is that some SWR banks don't necessarily become writeable the same way as on the Master. eg the original Solidisk SWR boards used the 6522 userport to determine write location.

Most modern variations toggle write enable along with chip select (so writing the FE30 will enable that bank for writing as well), but it's not universal.
Last edited by sweh on Mon Jan 14, 2019 4:58 pm, edited 1 time in total.
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Re: POLL: How much Sideways RAM?

Post by hoglet » Mon Jan 14, 2019 5:02 pm

Another gotcha (on Steve Picton's latest RAMROM board) is that 4 of the 8 RAM slots have self-write protection.

i.e. A write from code in normal RAM will succeed, but a write from code in the sideways RAM slot itself will be blocked.

Dave

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Re: POLL: How much Sideways RAM?

Post by dominicbeesley » Tue Jan 15, 2019 11:21 am

This is interesting, I will follow the poll with interest

I've put "all the ram in the world" as my blitter board has 1024K of RAM and 512K of Flash that can be configured to be used partially as SWRAM, Battery Backed SWRAM or Flash in the ROM banks as well as a shadow OS.

I like the idea of your OSRAM Cmorley - if you have some for sale I'd like one - also do you mind if I copy your API? Is there any software that uses/relies on this?

I've been wondering about the various RAM/SWRAM APIs recently and how popular they were. And how much software relies on the different types. I really need to do a survey of the various RAM/ROM expansions and their hardware/software/API differences:
- JIM/DataCentre/Musicx000? (i.e. take over the whole of JIM)
- "properly" paged JIM i.e. only respond on one major page (as I read the original spec!)
- Other JIM RAMs
- Simple SWRAM i.e. ram in a rom socket with a simple R/W clip
- Less Simple SWRAM i.e. ram in a rom socket with R/W and bank switching clip(s)
- Aries B32, other Aries
- Ctorwhy - I think this allows writes to the Flash direct? I seem to recall it causing problem for me?
- My blitter which allows access to Flash/SRAM via JIM and paging and OS banking - non-orthogonal, unfinalized API!
- Integra B
- Anyothers I should consider?


How much software is specific to each API, I guess most stuff just probes for RAM by writing to banks and seeing what happens?

D

Edit: added integraB
Last edited by dominicbeesley on Tue Jan 15, 2019 2:02 pm, edited 1 time in total.

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Re: POLL: How much Sideways RAM?

Post by sweh » Tue Jan 15, 2019 5:57 pm

dominicbeesley wrote:
Tue Jan 15, 2019 11:21 am
- Ctorwhy - I think this allows writes to the Flash direct? I seem to recall it causing problem for me?
With the RAM/ROM board, the Winbond W29C020 flash chip has write protection built in, so a command sequence needs to be sent (anyone who followed MartinB's work will be familiar with this). But the Flash chip may return recently written data even if it's not persisted. So I put a delay in my detection code to handle that case. (Read byte; EOR #&FF; write byte; delay a while; compare byte. Without the delay it'll think it's RAM; with the delay the compare fails so it thinks it's ROM), which may impact a number of games/loaders that try to autodetect SWR and get it wrong as a result.
- Anyothers I should consider?
Solidisk 2M128. 8 banks of RAM, 4 additional ROM slots; RAM can be used as SWR or Shadow or buffer. Uses ROMSEL to select the write bank, but also has a variation of ACCCON to select the shadow/buffer mode; basically it can page in 2 of the RAM banks - either C/D or E/F - over &2000->&8000.

Original Solidisk boards (uses Userport output to select the write bank), standard ROMSEL for read. Which made it easy to load ROMs (?&FE62=15; ?&FE60=slot ; *LOAD IMAGE 8000) 'cos one ROM could write to another slot :-)
Last edited by sweh on Tue Jan 15, 2019 5:59 pm, edited 1 time in total.
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Re: POLL: How much Sideways RAM?

Post by GadgetUK164 » Tue Jan 15, 2019 6:00 pm

96K

32K using a DS1230
64K RAM using one of the boobip chips.
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Re: POLL: How much Sideways RAM?

Post by KenLowe » Tue Jan 15, 2019 11:14 pm

I've got 4 x 16k RAM banks in my IntegraB. It's possible to add another 8 RAM banks (via 4 x 32k RAM ICs) to the board, but I generally use EPROMs/ EEPROMs in those slots. I've got other beebs, with other ROM / RAM expansion boards (2 x IFEL + 1 x kjell / Sundby), but I find the IntegraB to be the most robust / flexible (and it also has shadow RAM / RTC).

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