Psion and ROM cartridges

[RalfR]

OK, I only tried it for a quarter of an hour, that's probably not enough. But I know for a fact that the "N" version crashed immediately in SMSQmulator the first time I tried it.

I probably need to use it a little longer.

[Wicksy]

Had Sinclair produced the Xchange ROM, it would have been for their unreleased QL successor, described in some places under the name "Enigma".

[/quote]

Dilwyn, I would argue you are partly right. Of the 3 mentions in QL User the upgraded QL is mentioned twice, but all 3 say Sinclair were considering a plug-in ROM card option for the existing QL.

[Wicksy]

1. Am still missing understanding on the 16 devices total in regard to is it just what gets plugged in to the expansion bus or on all ports (eg. a printer on SER2), if anyone will indulge?

2. And how, say the super gold card with a printer and the full 4x floppy drives connected is seen in the 16 device total. Is it 5 or 6, with the card itself included, or even just the card itself as 1?

3. With most expansion modules having at most 4 card slots (just a German model having 5), was it a case of 2 daisy chained modules to gain the full 8 card slots and then each card being counted as one device unless if offered more than one function, such as a gold card?

[Pr0f]

you are still using "slot" which is a virtual concept from Sinclair during the design of the QL - with device - which is any type of element that can do I/O in the Operating System - it may even be a virtual device that doesn't need to talk to any physical I/O addresses (PIPE, RAM disk, DEV and SUB devices). The Devices can be enumerated from 1 to 8 - so you can technically have upto 8 devices of one type - the limitation would be the physical capability to host these devices, or the memory required to support them.

Sinclair only offered the expansion port on the original QL - 3rd party manufacturers have designed back planes that can support more plug in cards - the technical guide explains that upto 16 of these (16 x 16K = 256K), which would then occupy the last 256K of memory in the unexpanded QL's memory map, could theoritcally be used. In practical terms - signal degredation, signal path length and all sorts of other physical constraints - such as power, physical size will mean that a more likely number is about 4.

Gold and Super Gold cards, emulators and Q68 all provide more memory than the 1MB memory map of the QL allowed for, but they also effectively remove the slots for expansion I/O cards.

So to come back to devices - the QL has 2 built in serial ports - SER1 and SER2, but remember you can have upto 8 devices enumerated - so you could potentially add SER3 to SER8 to a QL system - but you'd need to provide the hardware to do that. Likewise there are 2 Microdrives - MDV1 and MDV2 - but again the rule of 8 allows for 6 more. If you have a Vdrive (external emulated Microdrive), this can emulate all the remaining Microdrives in just one device - this device plugs into the Microdrive expansion on the right hand end of the QL - you could also plug in a Sinclair ZX Microdrive into that connector - and get an MDV3 - Sinclair never produced any external Microdrives for the QL.

Finally - coming back to plug in expansion cards - there is nothing stopping you adding multiple device types - and indeed many of the expansion cards offer combinations of devices and often memory, along with the necessary drivers and commands to make use of that in the OS.

The Golden rules:

• No two devices can occupy the same physical address space - there will be contention if one of them is not disabled.
  
  Any device enumated to the system could be overwritten or expanded by an expansion card
  
  To be able to use the device - a driver and some commands will need to be registered to the system.

[dilwyn]

Would be interesting if someone with the necessary knowledge was able to work out how much addressing space was needed to make an Xchange on ROM to see if it could fit on a QL system. Then actually try making one if thought feasible. Presumably it'd be roughly the same space as required on the original Thor systems. While it would be convenient having it on ROM/EPROM, that would be balanced by the need to be able to update it. I use Xchange quite often. I'm just so used to running it from disk on all systems I suppose.

[Wicksy]

I'll look on in interest if someone does.

[Derek_Stewart]

Hi

I thought that to put Change or Psion apps in ROM, was easy to do.

But Quill, Abacus, Easel, Abacus executable files are over 50Kb in size each.

Xchange v3.90m executable is 188Kb in size.

Clearly all larger than 16Kb for inclusion to the QL ROM slot area.

I think the conversion from executable to ROM file is easy. But how to get the QL system to register the new files that exceed 16Kb ROM size will need an change or extension to the operating system.

[Wicksy]

This would be to put it in the final rom area of the memory map Derek which has 256k.

I appreciate that running just Quill with only 128k was problematic, but with it now loaded in the rom area, it frees up the usable 96k of ram left.

[RalfR]

This also raises the question of whether the Psion programs in their current form are even romable or whether they necessarily have to run in RAM?

[Pr0f]

One approach that might work - and not require recoding of the xchange suite that is available for the QL - is to provide a ROM device - a read only version of a RAM drive. Provided there was room to locate the ROM in the QL memory map, then it would just be a matter of populating the ROM contents initially.