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| | Previous Messages | Posted By
Crown
on 2025-04-19
15:57:54
|  Re: Cartridge for Burst mode
Looks very neat. Let's make this real ! |
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Posted By
MMS
on 2025-04-19
14:03:11
 | Re: Cartridge for Burst mode
Nice! The fast serial protocol may give a new life to some of our beloved floppy drives.
And yes, without thae high speed the 1581 does not have too much sense at that price tag. Do not take me wrong, i like the 1581 but even the new version costs a lot after printingbthe house order the PCB from China not to mention getting a 3.5" floppy drive in good condition. Almost the same price as a factory 1571.
With the high speed AND big 880KB size it is a great device even at that high price.
Comment:Still TCBM2SD is a winner is speed and size :-) |
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Posted By
ytm
on 2025-04-19
05:42:45
| Re: Cartridge for Burst mode
I played with this idea last night (I have 1581 replica too).
This looks viable. Maybe IEC sockets should point to the back instead of the sides, I'm not sure.
Clock generation and address decoding sections were stolen from ReSeed, 64K ROM taken from tcbm2sd.
ROM would have to intercept at least the LOAD vector and use Pasi Ojala's code for fast load. Ideally it would contain big chunks taken from C128 Kernal that detect slow/fast devices on IEC bus.
There is a ribbon cable socket for 1541 parallel burst cable (matching DolphinDOS cable pinout) and another one for the the second CIA port, with power - just in case. CIA has /IRQ line connected, although that's not used for burst.
TOD clock is not connected to anything. Maybe an ATTiny would fit somewhere to generate 50Hz clock from its internal oscillator.
Need to check CIA datasheet to be sure it behaves in the same way as SID regarding the CPU bus.
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Posted By
MMS
on 2025-04-18
15:07:17
| Re: Cartridge for Burst mode
Actually the C64 owners worked out an their solution years ago for the fast serial protocol (burst mode too?). (Pasi Ojala is a well known HW guy)
Sure it uses CIA, I am curious how well it could be implemented on the 264 HW.
1581 maybe a too expensive beast (my 20pcs of assembled 1581 PCBAs lost at the Hungarian Post, ridiculous), but 1571 is rather affordable, costs only 2x more than an 1541/II, and it is MFM / CP/M capable, double sided 360KB drive, and with burst mode almost as fast as Jiffy.
Not to mention I have one, and one of the coolest looking floppy drive Commodore ever released :-D
As Jiffy realization on Plus/4 is not optimal, realizing the Fast Serial/Burst mode on 264 series would be really optimal solution for IEC bus. For the parallel bus we already have TCBM2SD :-D
I dunno if the IEC2SD is able to work in Burst mode, it would be great... 
https://csbruce.com/cbm/hacking/hacking19.html |
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Posted By
SukkoPera
on 2025-04-18
12:01:27
| Re: Cartridge for Burst mode
Even if not many people have a 1581, it is easy to build one. It mostly uses common components save for a CIA and a WDC 1770/2 floppy controller and a couple of years ago many people cloned the mainboard.
... Including me! I have a working design, I never released it since I was sure it would end up on eBay in a pinch at crazy prices but if this project becomes a reality I would be happy to release it openly. |
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Posted By
BSZ
on 2025-04-18
09:43:11
| Re: Cartridge for Burst mode
Several thoughts came to mind on the subject...
The CIA clock can probably be solved, as @ytm says. (So that everyone understands why this is interesting: the timers in the CIA run from this clock. But the clock in our machine is not constant, so the speed of the counters would also vary. Even if we don't want to use it as a timer, the operating speed of the shift register also depends on this.) However... I haven't wanted to buy of this chip yet, but I'm sure it's getting rarer/more expensive. For this reason, I would certainly not think of implementing such a CIA.
And then... Do enough people have such a floppy drive to make it worth designing hardware for it? It can be done just for fun, of course, but its usefulness is questionable. A conventional fastloader is faster than this, this would typically be useful for tasks that are no longer done with such retro machines. That was quite an improvement 40 years ago, but today, in 2025, we would typically expect more.
I write this as, I recently made an add-on for SD2IEC drives that would make it just fine to use.  (@ytm: I haven't forgotten about the burst block commands, I've just been doing other things lately.) Regardless, it would be an interesting project, with few advantages in my opinion. |
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Posted By
ytm
on 2025-04-18
07:55:27
| Re: Cartridge for Burst mode
CIA would have to be clocked in a similar way how it's done for SID cartridges by about 1MHz signal.
There is already a difference between C128 (0.98... MHz PAL) and 1571/81 (1MHz exatcly) clocks, buffers are not required.
It's synchronous and timed by CIA timer. On C128 one bit is shifted in/out every 4 ticks of CIA phi2 clock. It doesn't speed up when CPU is switched to 2MHz mode.
Regarding IEC I think that having something like UltimateII+ solution would be the easiest one: two pass-through sockets on the cartridge - one for drives and one for connection with a short cable to mainboard IEC port. This way Kernal can be used to talk with all the devices.
Parallel port from CIA for 1541 burst would be a cherry on top .
It may seem wasteful to use CIA only for its hardware shift register, but that's exactly what C= did with plastic C128D. |
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Posted By
Crown
on 2025-04-18
07:20:06
| Re: Cartridge for Burst mode
Yes it is for 1570/71/81.
Yes one possible approach is a CIA based one, there the issue could be the different clock, would the timings of the protocol work if the CIA is driven with the Plus4 clock? If not than it would need some read/write buffering mechanism to pass the data between the two differently clocked domain, but that might be way to complex.
The other solution is adapting an XUM1541 and family based solution, to interface to the Cartridge port instead of USB. This probably requires an additional power supply as well.
As for the physical connection, I see two solutions: the cartridge has an IEC port, and the drives are connected directly to this port, and the regular IEC remains for other drives.
Alternatively an IEC splitter device can be constructed which connects the drive to both the IEC port on the motherboard, and the IEC port on the cartridge.
The parallel port is an optional bonus, parallel port mods exist for each drive, and could be used here as well. And it could be used for 1541 drives without burst, in a C16 where there is no userport. |
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Posted By
ytm
on 2025-04-18
06:57:06
| Re: Cartridge for Burst mode
@Crown mentioned 1570/71/81, so yes it's about fast serial with hardware shift register. This can be done, but the cartridge needs CIA just for that and CNT/SP lines need to be routed back to IEC connector.
It's not difficult to program for: devices agree on the protocol using standard IEC communication and then switch to fast serial. It can be done on C64 (with h/w mod) or C128 in C64 mode too: https://a1bert.kapsi.fi/Dev/burst/
Another meaning for 'burst' would be parallel connection to 1541, but again CIA/VIA is needed because (unlike 1551) it relies on hardware handshake. |
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Posted By
gerliczer
on 2025-04-18
06:39:24
| Re: Cartridge for Burst mode
Burst Mode in Commodore IEC Bus parlance is a form of serial transmission driven by the hardware shift register of the *IA, AFAIK. As VIA had a shaky implementation of this feature, 1540/1541 couldn't do Burst Mode transfers reliably. Or did I misunderstand something again? |
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Posted By
Crown
on 2025-04-18
06:17:48
| Cartridge for Burst mode
Has anyone attempted yet, to design a cartridge to enable burst mode for 1570/71/81 drives?
Basic design constraints: requires IEC connector on the cart, custom ROM either in the cart, or replaced in the machine, optional parallel cable connector on the cart so that it can work with C16 as well.
Device ids would be in 12-15 the range. |
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