Virtualc64: Ram Expansion Unit (REU) and geoRAM

[Alessandro1970]

Hi,
Is there a way to add the REU to the VirtualC64?

Demo:
BluREU_Crest_demo.prg.zip

[Ottavius]

Great. Does this memory expansion also work with Geos?

[Alessandro1970]

I do not know, the Geos had a dedicated memory called GeoRAM.

https://en.wikipedia.org/wiki/GeoRAM

[dirkwhoffmann]

REU is not supported yet, but it shouldn't be too difficult to emulate it.

[Alessandro1970]

Hi Ottavius,
I found this on wiki:
The REUs came in three models, initially the 1700 (128 KB) and 1750 (512 kB), and later the 1764 (256 kB, for the C64).
The GEOS operating system had built in support for the REU as a RAM disk, as did the C128's version of CP/M, and some disk copy programs used the REU to facilitate high-speed copying with a single disk drive. GEOS as well as other programs even used the REU for quick memory transfers within the host machine's main memory by storing a memory block into the REU and then fetching it back to another location. Using this method, only the actual data to be transferred needed to travel on the machine's data bus—unlike the ordinary method, which had the computer's CPU do the transfer, thus spending at least three quarters of the bus capacity on instruction fetches and only one quarter or less on payload data.
I really like Geos and as far as I've tried on VirtualC64 it works very well, try it with mouse emulation.

Note: Using a mapped-in page scheme, the geoRAM was much slower in operation than the DMA-driven REU cartridges; hence, not much software other than GEOS actually supported it, so REU was the best.

[Alessandro1970]

_1764_ RAM EXPANSION UTILITY DISK
Side A:
1764-utility.d64.gz
Side B:
1764-utility-geos.d64.gz

[Ottavius]

Would not it be better to add the emulation of the GeoRAM instead of the REU?

[Alessandro1970]

Ottavius, ask to Dirk about it, open an issue if you need it.

[dirkwhoffmann]

I didn't look into the details yet, but it shouldn't be too difficult to implement both. I'll look into it when I'm done with the VC1541 improvements.

[Alessandro1970]

Thank you Dirk

[puleyo]

Georam would be an another great add-on for me too.

[dada08ms]

Hello,
I am very happy when I will can use the REU in this great emulator; so we will can use the software RAMDrives with the VirtualC64.
Do you think that it will be possible to choose the amount of memory to associate with the REU ?
[256kb, 512kb and at least 1mb]

[Alessandro1970]

Originally the REU for commodore 64, I think, it was only 256 kb, but I can be wrong.

[dirkwhoffmann]

I did some research and found out the following: The REU's internal architecture is much more complicated than I thought originally, so I'm not sure if it is worth implementing. In contrast, the geoRAM seems to be quite easy to implement, because it simply has to blend in a certain page of the external RAM (no complicated memory transfer is required).

[Alessandro1970]

GEORAM is a 512K memory expansion unit made by Berkeley Softworks for use with GEOS. It can also be used for other programs. There are several programs that support GEORAM though, for example Maniac Mansion GOLD.
Neoram drive also works with georam (to use georam instead neu as ramdrive).
A ramdrive for NEO-ram and compatibles (i.e. GEOram).
NEOram being a modern batterie buffered version of georam with up to 2mb.
Fully compatible to GEOram so you can use this with georam just as well.
The BLOCKS FREE is hardcoded to 2mb though, but can be used with 512KB.
check label "ramsize" and change i.e. to #$07 for 512 KB
Device-No is set to 2.
Use POKE 2,X to set device to X (8 also works btw)
also nice: use 1 and you can press SHIFT+RUN/STOP in directory listing!

Commands:
LOAD"$",2 for directory
LOAD"file",2(,1)
SAVE"file",2(,1)
VERIFY"file",2(,1)

further commands:
to INIT the drive use "arrow-left" as first char of filename! I.e.
LOAD"<=",2,1 or LOAD"<=FILE",2
will format the ram expansion.
f that happens accidentally, repair with NEOram Monitor since
only 4 bytes were overwritten

to SCRATCH a file use POUND-sign (%) as first char in filename:
LOAD"%file",2,1
will scratch the file named "file".

Code currently at $ca00 so the LOAD-limit is about 193 blocks.
for basic loaders: about 153 blocks.

This version initialises the kicker that remains in NEOram.
You can launch it with SYS57000 or SYS57E3 anytime!
Due to the batterie buffer it is resistant and
can be launched even after several days/weeks/months.
Source: https://csdb.dk/release/?id=61122&show=summary

[Alessandro1970]

Maniac Mansion GOLD [neoram]
https://csdb.dk/release/?id=84165

[Alessandro1970]

...NEOram emulation could be a solution for geos, ramdrives and some software.

[dirkwhoffmann]

GeoRAM will be available in V2.3 (code is already checked in, branch V2.3). The NeoRAM seems to use the exact same hardware, so I guess it will work, too (at least, the NeoRAM drive application is working fine).

[Alessandro1970]

Georam works fine.
Thanks