Physically byte-swapped IDE [AKA twisted cable]

[Badwolf]

https://atari.8bitchip.info/idepc.htm

I assume this is because not only is the data byte-swapped, but all the IDE control channels too.

Sure ... if you twist the cables, you also swap hardware registers and software that isn't designed for that will not be able to do anything meaningful to them anymore.

Cool. Perfect. Thanks, guys. Armed with the above confirmation, a debug build of EmuTOS and Alex's link to PP's twisted driver I was able to prove it's doing what I thought it was doing and access an SD card written on my Mac and transplanted.

It autoboots well under ET, TOS locks it up trying to boot from it (presumably a command that isn't getting a response, leaving it in an inconsistent state) then running PP's driver twice (first time to unlock it) works.

I'm not sure where I want to go with this next, but it's nice to see it working.

Cheers,

BW

[alexh]

Is HW byte swap noticeably faster?

HDD performance on retro systems is always a thorn in my side so anything that can be done to improve responsiveness is good.

I'm not an expert in TOS but in AmigaDOS you can get significantly better performance by adding a configurable size cache (addbuffers). Is that something you can tweak in TOS?

I'm also interested in what volume size limits and partition size limits there are with the various TOS versions / filesystems/ drivers and how best to overcome them. I've not seen it written down anywhere in one place.

[Badwolf]

Is HW byte swap noticeably faster?

I need to dig out the transferrate program (again from PP, IIRC) & clock them. Only really had time to verify behaviour yesterday.

I'm trying a couple of different approaches. I've got an adapter board that allows master/slave configuration and also byte swapped/non-byteswapped connection to the host.

Option one is to have a master, partitioned for Atari to boot from and a removable slave to ferry between the Falcon and modern hardware, employing software byte-swap.

Option two is to byte swap the whole shebang and only need one device that can be removed and plugged into the Mac/PC. This will auto-boot under EmuTOS, but nothing else yet.

Option zero, I should mention, is to not byteswap anything and just use EmuTOS (or PP's driver) and a PC formatted device. This will work fine, but will have to logically swap everything, so will be slower.

Two is nice because of speed and also you can fire up Hatari with your normal configuration easy as you like, but the complications around getting it to autostart exist. Like I say, normal TOS actually blocks the drive when trying to boot (the activity light stays on).

All a bit of fun, though. :)

BW

[Cyprian]

Is HW byte swap noticeably faster?

on the ST yes, because shifting instructions are rather slow on 68000 processor. In case of Falcon - I have no idea - 68030 has cost less shifting due to a barrel-shift .

I'm not an expert in TOS but in AmigaDOS you can get significantly better performance by adding a configurable size cache (addbuffers). Is that something you can tweak in TOS?

Disk drivers (e.g.HD Driver/ICD/HUSHI) reserve memory buffer for the cache (it size can be changed) and it is active by the default.

I'm also interested in what volume size limits and partition size limits there are with the various TOS versions / filesystems/ drivers and how best to overcome them. I've not seen it written down anywhere in one place.

Max partition size depends on the TOS version:
1.00-1.02: 256 MB
1.04-3.xx : 512 MB
4.0x: 1024 MB (but I tested 2GB on my Falcon and it worked fine for me)

In case of MiNT - I have no idea, it has its own drivers, therefore my guess is that its partitions can be really big.

[JezC]

@Badwolf I've taken a simple route for now...an IDE cable with one SD to IDE plus one CF adapter fitted at the same time. The SD is formatted for the Falcon to boot from while the CF card is formatted to work with the PC as well as the Falcon.

So, I can move files between PC & Falcon via the first partition of the CF card and copy them onto the SD card.

My next plan was to get the Falcon connected via Ethernet (or WIFI) but it can't use the cart port as that has dongles for my music s/w permanently plugged in.

I'll be following this with great interest - and any suggestions for suitable Ethernet/WIFI solutions would be most welcome too!

:thumbup:

[Cyprian]

I'll be following this with great interest - and any suggestions for suitable Ethernet/WIFI solutions would be most welcome too!

https://github.com/PiSCSI/piscsi
https://www.piscsi.de/
I read somewhere there is a support for DaynaPort network card for Atari

[czietz]

Fwiw, I once made a prototype of a standalone adapter that adds the Smartswap* feature to any Atari. However interest was too little to make a Falcon (i.e. 44-pin) version. :(

https://forum.atari-home.de/index.php/t ... #msg247565

* Smartswap -- known from our Thunder and Lightning ST -- is hardware byteswap just for the data, and brings the corresponding speed increase while keeping the compatibility with any driver.

[Badwolf]

Fwiw, I once made a prototype of a standalone adapter that adds the Smartswap* feature to any Atari. However interest was too little to make a Falcon (i.e. 44-pin) version. :(

https://forum.atari-home.de/index.php/t ... #msg247565

* Smartswap -- known from our Thunder and Lightning ST -- is hardware byteswap just for the data, and brings the corresponding speed increase while keeping the compatibility with any driver.

Very cool! :)

This is something I pondered playing with too, once I understand the IDE protocol better (for now I wouldn't know how to identify data versus register accesses). Now that CPLDs are starting to come back into availability again it could be a one-chip board.

BW

[Cyprian]

Fwiw, I once made a prototype of a standalone adapter that adds the Smartswap* feature to any Atari. However interest was too little to make a Falcon (i.e. 44-pin) version. :(

https://forum.atari-home.de/index.php/t ... #msg247565

* Smartswap -- known from our Thunder and Lightning ST -- is hardware byteswap just for the data, and brings the corresponding speed increase while keeping the compatibility with any driver.

nice addon,
whats is a difference between that and a twisted cable?

[czietz]

nice addon,
whats is a difference between that and a twisted cable?

As I wrote. Smartswap only swaps the data bytes, in contrast to a twisted cable that swaps everything and hence needs a specific driver.