Atari ST mass storage interfaces

  Compact Flash adapter for ACSI port

  This is very simple interface, with only 3 chips - good even for DIY (Do it yourself)  .  Supports 1-2 CF cards as Master & Slave.
Features:  Works with Atari ST, STE, Mega STE and TT machines. Usable CF cards: newer ones, which support faster transfer modes. Recommended is Sandisk Ultra - with it some unseen speeds on ACSI port are possible.

p/ACSI_CF_drvi1.png   p/ACSI_CF_T1.png

  Atari ST ACSI port can much more than Atari claimed (in AHDI DOCs) :  almost 2 MB/sec !  With this simple adapter, so high speed is possible only with some CF cards. Knowing so far: Sandisk Ultra is such. Requirement is that CF card support 8-bit transfers in Multiword DMA mode.  Slave card, 1GB Kingston supports it not, so adapter uses it in single-byte mode - what means transfer speed of some 350 KB/sec. Still not too bad - may be good for some copiing. See video ...

p/SandiskU2.png  This card rocks ! Bought 3 years ago for 40 Euros, now price is about 20 . 2 GB is in fact enough for all Atari needs, especially if you keep your valuable data on PC, DVDs, and can easy and fast copy to CF card   what want to use in next period.

Interface requires proprietary (custom) drivers - works not with regular drivers for Atari hard disks. Driver is ready for Compact Flash cards - DL below .
Driver/partitioning features:  TOS/DOS compatible partitions, 14 maximum per media. No first partition special size limit. All partitions can be up to 512 MB ( TOS 1.04 and higher) . It means very easy data transfer with some PC - no need for special SW to access files. Low RAM usage. 100% ASM code.

Autoboot: This is not possible for this adapter, unless doing some changes in TOS ROM. Mod for TOS 1.04 and 2.06 will be published soon.
Usage: no need to open machine - while it is not turned on just connect adapter to ACSI port, insert CF card and ensure power to adapter. Then may turn on power on ST(E) . Best is to load driver from AUTO folder of floppy.

Work with other ACSI devices: I made quick tests with ICD AdSCSI Plus ST, UltraSatan and Mega STE with internal adapter.  Pass through of ICD worked not, so I made splitter - then can connect 2 devices parallel. ACSI-CF adapter is made so that 'uses' IDs 4-7, so other devices must be in range 0-3.
The results are not perfect, but it seems that can be used. I tested with hard case: 2 CF cards at once + ICD or US.
With ICD DMA transfer worked not, only bytewise, while with US was opposite . Interesting... But bytewise worked not because of Kingston - with Sandisk it worked too. With Mega STE everything was perfect - all drives/cards worked well.  In any case, such combinations are not for regular usage, only for some file transfers. And it worked.


Big mess on desk with SCSI drive - and there is even PS not visible here ...


Little better with UltraSatan. Running EPIC from CF card, after copying it from US.

Component list:  19 pin Sub-D, male. If want to use together with other ACSI devices, need + 2 x 19-pin Sub-D female +  another male for splitter. It is hard to find such Sub-D connectors - I needed to saw 25-pin ones.
 GAL 16V8, 74HCT574, 74HCT221, 2 x BAT49 or similar schottky diode (but 1N4148 will work too in case). 1 LED for activity, some resistors and capacitors. CF socket(s) ( or IDE connector + IDE-CF adapter ). PCB . Some cable .
Power:  you need to supply stabilised, accurate  5V (+-5%) to IF . Simplest is to take it from Atari self .

Schematic, board & other

Driver SW  runnable driver for Sandisk master in DMA mode,  and optional slave in PIO mode . For ST, STE, MSTE, TT .
   Needs PP TOS/DOS compatible, partitioned media :  TOS/DOS compatible images

  Project in development: IDE/ATA disk interface for Atari ST(E) Cartridge port:
Writing speed is over 2 MB/sec.  Reading speed may be up to shown 2350 KB/sec ! But so high speed only with optional small mod. in ST(E) - need to cut 1 line and lead out 2 wires, then connect them with adapter.  When no mod. in machine max reading speed is about 1400 KB/sec. So, it's on user to decide how to use and set it.

Interface requires proprietary (custom) drivers - works not with regular drivers for Atari hard disks or IDE CD ROMs. Hard disk driver is ready for hard disks/Compact Flash cards up to 2048GB   (LBA48) .
Driver/partitioning features:  TOS/DOS compatible partitions, 14 maximum per media. No first partition special size limit. All partitions can be up to 512 MB ( TOS 1.04 and higher) . It means very easy data transfer with some PC - no need for special SW to access files. Low RAM usage. 100% ASM code.

High speed is achieved by using special data transfer mode - where CPU is used only for addressing RAM, but not in transfer self - I call it semi-DMA mode. Then transferring 4 bytes requires only 12 CPU cycles instead usual 20 .


Data transfer under windows XP:  only first partition on removable drives (CF cards via USB reader) will be accessible. How  to override it see here  .  By regular IDE hard disks no such limit, but connecting to PC is harder.
  It works with Falcon too, in read-only mode. Reading speed is about 2730 KB/sec (via driver) when CPU is set to 16MHz.

   Autobooting from CATA (cartridge port IDE IF) :

Boot is little different than boot via regular hard disk ports as ACSI or AHDI IDE .
 It happens before RAM test of TOS 2.06, before floppy and regular hard disk boot.
 But it changes not much whole usage. Even possible to prevent by holding Alt after reset.
  This is new driver concept: no MFP, timer (C) usage at all in driver core. Timing goes via CPU code, after detecting rough speed.  SpeedR   8  -  means 8 MHz ST speed.


Something useful for case of multiple drives/cards attached: Good utility

Hard disk driver considerations :  so high speeds as by CATA and ACSI-CF make disk cache complete useless. Because transfer from disk is faster than copiing from RAM to RAM. Especially with fast access CF cards. Driver is maximal possible gaming compatible:  low RAM usage, no Timer C, any MFP reg. usage, easy movable in High RAM for adapted games.  Because there is no any benefit from using AHDI partitioning, DOS type is supported. But with TOS/DOS compatibility for all partitions (max. 14 accessible at once, due to TOS limits). With driver goes easy to use GUI partitioning program. For CATA and ACSI-CF must use custom drivers - regular Atari drivers will not work. There will be only TOS/DOS compatible variant, no DOS with BIGDOS.PRG type free variant.

  IDE timing problems by Atari ST serie

Internal IDE interface, AHDI compatible

  This project is for people with some soldering and electronical knowledge. Unfortunatelly Atari ST machines have no internal bus connectors (except Mega ST serie), and soldering is only way to make some specific hardware extensions.

  This interface will allow to connect IDE hard disks, CD ROM drives and other Atapi compatible devices to an Atari ST(E) computer. It is AHDI compatible, and all standard drivers should work on with it. Additional it supports optional ROM upgrade to TOS 2.06 (what is at address $E00000, and has 256KB size) in older (ST) machines, which have 192KB ROM at address $FC0000 - with 4 x 27512 Eproms.


GAL listing  JEDEC file

There is a little simpler version of this interface - with GAL16V8, without 74HCT245 line drivers, and for 2 chip TOS 2.06 (optional)

There is Eagle SCH and BRD project of IF for Atari Mega ST toosimpler IDE IF

Atari ST and hard disks - Little history and overview.

IDE hard disks - history, retro usage .

PC related software:
Drive Image and file transfer program for Windows - GemDos support
Same as above - for Linux

Atari ST software from me:

Hard disk driver for DOS partitioned disks  It can handle up to 14 FAT16-BigDOS partitions from drives of capacity to 128GB. Needs freeware program BigDOS for work. Max part. size is 2GB. Only for IDE interfaces. Falcon compatible.
idedp.png                              Speed with twisted cable:
twspe1.png   twspe1.png
Note: access time is so good because is measured only inside 1 partition.
Bigdos homesite

Image runner - Run games from ST, MSA images on real Atari ST, without writing floppies.

Fast video playback on Atari ST(e) in fullscreen mode  25 frames/second with 320x200 - yes, it is possible!

Hard disk speed test  - GUI program with direct HW access testings for diverse interfaces, with speed tests via installed driver + reliability tests. It can measure even CPU slowdown in case of ACSI transfers.

Old versions of speed test SW :

IDE hard disk speed test - Test raw transper speed, access time, diverse modes.

First 3 test is with direct hardware access. 'D' is for comparing installed hard disk driver's speed with direct access speed. If driver is not installed, it will show garbage.
Blitter tests work only on STE or Mega ST machines. HOG mode may crash.
Random access/read is average time of reading one random sector at any position on whole disk with direct access (R test). T test  is for same, but on C: partition only, via installed driver. It may be faster if partition  not occupies whole disk, otherwise is little slower. By Flash drives, as on pic left average access time is very fast - no mechanic.
Of course all tests are made with interface made by this project.

 New version with ACSI/SCSI direct access measuring.
  IDE-ACSI-SCSI speed test program

maxt40.png 40 GB Maxtor drive results.
wdc60.png60MB WD Tidbit 2.5 inch drive. ST is too fast for it...

Hard disk speed test  version without direct hardware access - so it will work with any interface. Needs of course installed hard disk driver. May select which partition to test:
Test is made with same Transcend IDE-Flash drive as above. Lower data rate is result of different hard disk driver - but access time is little better.

  Atapi CD/DVD read speed:
Of course, interface allows attachment of CD/DVD readers.
This is measured with new, fast DVD drive. But datarate is very low. Reason is required byte-swap, because standard CDs, DVDs have Intel byte order.

This is same drive, but measured with direct read wihout byte-swap. Speed is as by newer hard disks.Big speed will be required for smooth video playback - see below.

Note that random read time depends on how much disk is full. First test is with CD only 1/3 filled. Second is with full DVD. Capacity will be shown correct only by data DVDs, not DVD videos.
The program : CD/DVD ROM speed meter

Seltos.prg - Manages usage of ROM-TOS 1.00, 1.04 and 2.06 on any ST machine without EPROM change or reprogramming.

idepc.htm - Hard disk driver for Atari with this interface, but for PC format partitions.

Useful links:


Copyright: P. Putnik

Last revised: July 2011

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