As you may know I’m busy with pimping a Commodore SX64 and trying to bring it into the 21th century. Since it is fairly old technology loading a program is painstakingly slow. Traditionally modded kernals or cartridges are used to install fastloaders. Modern alternatives like SD2IEC and pi1541 are compatible with them but still are slow. A MagicDesk Cartridge has improved loading times because its memory is directly connected to the CPU instead of a slow serial bus. The MagicDesk Cartridge can store upto 512KB (approximately 2000 blocks) versus a regular disk that holds 170KB (664 blocks).
The MagicDesk Cartridge is a cartridge that can bankswitch upto 1024KB (my version is just 512K) into the memoryspace at $8000 of the Commodore. Swapping is done by writing a byte to IO1 area ($DE00-$DEFF). The first 7 bits selects which bank is switched in. Setting the 8th bit disables the cart. In the first bank a autostarting menu is stored which takes care of the bankswitching, moving the selected program into memory and run it. With some magic also regular 8KB cartridges can be stored and used. Select the right bank with ‘POKE 56832,<bank>‘ and reset the Commodore with ‘SYS 64738‘. With patching other cartridge switchers would be possible.
The original expansion board was removed from the SX64 and replaced with a slighty larger expansion board with the MagicDesk Cartridge added to it. To enable the use of regular carts, it automagicly disables MagicDesk cart when a regular cart is inserted. A switch also can disable the internal cart and a button can reset the SX64 since it is lacking a reset button.
Only one of the 2 5V supply (pin X an Y on the expansion port) is connected to the cart, the other pin is the signal CRTSENSE which is pulled down with a resistor to ground. When no cart is inserted this signal is thus low and the cartridge signals are routed to the internal MagicDesk cartridge. When a cartridge is inserted both pins are tied together and the signal will be high and thus disabling the internal cartridge.
I’ll have a couple of populated leftovers on Tindie for sale.
On Tindie I didn’t found this device. Do you still sell them?
Whats the price Incl. shipping to Germany?
Thanks for your interest. I’m in the process of adding it to tindie.
Will be approx 10-15 eur/pc and 17 eur shipping with t&t on tindie.
I’ve just had a look on Tiniest and can’t find them. Have you any of them left?
Sorry for the long wait.. I finally got a couple for sale on TIndie.
DIrect link to it: https://www.tindie.com/products/Sjaak/sx64-magicdesk-internal-cart/
Will you be selling these any more? If not, is it possible to upload the PCB files to something like PCBWAY? Would love to add this to my SX64!
Thank you for doing it!!
The best add-on that I have been able to put to my SX64.
I have had some problem with the connection, apparently the yellow pin strip does not fit very well in the IDC connectors, I have replaced them, it is just a warning if someone happens to him.
I have taken the opportunity to mount the new strip of pins at the bottom of the PCB although it requires a laborious job of adapting the IDC cable but it remains clear to be able to change the ROM easily. A redesign of the PCB would be nice.
Can an AT29C010A be used?
Thanks, though I had every board tested with the supplied cable in my SX64. A 29C010 can be used but it cannot be written, use an EPROM programmer for that. I happen to have a lot of scrape 27c040’s here 🙂
You mean mount the pinheaders to the back of the board? assuming you can fold the cable in a certain way to accomodate this.
I just came across it, but after checking the tindie website found you were out of stock. Would you consider uploading the pcb files to pcbway, or will you be offering more for sale?
This week (or next week) I gonna order a batch of PCBs, along with a couple of these 🙂
There will be a restock soon.
PCBs will be in this weekend. Expect them to be available on Tindie soon!
I received my pcb today, thank you!
As I don’t have a suitable eprom yet, after installing the pcb and connecting the ribbon cable up to the SX I left the enable jumper open, thinking this would mean it was completely disabled and just acting like a plain cartridge port.
However when I power up the SX it reports 30719 basic bytes free instead of the usual 38911.
I replied directly with mail.
It seems there is a problem with the EXROM line.