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Ramdisk driver for DOS 2.5 and Sys-Check 2 512K RAM

Ramdisk DOS 2.5 Sys-Check 2 512K

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#1 E474 ONLINE  

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Posted Tue Jan 29, 2019 12:31 PM

Hi,

 

   Does anyone have a Ramdisk driver that uses (all?) the 512K RAM of a Sys-Check 2 card, and works with DOS 2.5 (not sure if DOS 2.5 would have to be hacked to work with such a big Ramdisk)? I have found a hacked DOS 2.5 that works with 256K, but am wondering if there is one that uses all the Sys-Check 2 memory.

 

   Any help would be appreciated!



#2 CharlieChaplin OFFLINE  

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Posted Tue Jan 29, 2019 1:24 PM

This should be possible, we need a new DOS 2.5 ramdisk-driver that does setup 4 ramdisks (e.g. using D5: - D8: ) with 128k RAM each. Not sure if this costs more RAM (for buffers, etc. resulting in a higher lomem) and if such a setup would still work with 4 physical drives, but surely doable...


Edited by CharlieChaplin, Tue Jan 29, 2019 1:25 PM.


#3 flashjazzcat ONLINE  

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Posted Tue Jan 29, 2019 1:47 PM

Perhaps use this as a starting point. It shouldn't be too difficult for someone competent to modify it to suit:

 

https://www.atarimag...5/SmartRam.html



#4 E474 ONLINE  

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Posted Tue Jan 29, 2019 2:51 PM

Hi,

 

   I was hoping for a single very large Ramdisk, but the link to SmartRam is very interesting (thanks!).

 

   Yesterday I had to patch the copy of DOS 2.5 I was using to use 4 drives, and I think the more Ramdisks you are using, the less physical drives you can use.

 

   Does anyone know if there is a limit to the size of Ramdisks that DOS 2.5 can address, or does the Ramdisk hide that behind a CIO interface?



#5 flashjazzcat ONLINE  

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Posted Tue Jan 29, 2019 3:05 PM

The volume size limits are going to be dictated by the DOS 2.x file system, since there are a limited number of bits available in the sector chain-links to describe the address of the next sector in a file. MYDOS overcomes this by using more bits for the sector links.

 

I believe DOS 2.5 is capable of handling 256 byte sectors (?), so if your RAMdisk driver dealt in DD sectors, I guess the DOS 2.x file system could handle 256K without any trouble. I'd have to reacquaint myself with some aspects of the file system in order to be more specific.

 

In any case, the RAMdisk driver just patches DOS references to the OS SIOV with calls to it's own transfer code depending on the drive number.



#6 Nezgar OFFLINE  

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Posted Tue Jan 29, 2019 3:18 PM

DOS 2.0 suports a max of 720 128 or 256 byte sectors, so ~90K or ~180K per disk.

DOS 2.5 Added ability to support up to 1024 128 byte sectors (Leaving 16 or so unaddressable by DOS) for ~128K per disk.

Maybe DOS 2.5 could technically adddress 1024 256 byte sectors for 256KB per RAMDISK?

DOS 2.0/2.5 can be setup for any combination of drives 1-8, details of which I posted about previously: http://atariage.com/...e-d2/?p=4132426

Drives 1,2 5-8 = 11110011 = 207

DOS 2.0 default of Drive 1,2 will show 3 = 00000011

DOS 2.5 Drive 1,2,8 may show 131 with PEEK(1802) = 10000011 in binary? I have not actually checked this - The 2.5 manual says default is 3, so maybe RAM Disks do not need to be included here.

Poke the new value into 1802, write DOS files to disk, and reboot.

The DOS 2.5 manual does indicate, however, that the practical limit is 5 drives enabled, since each enabled drive # (including RAM Disk) will raise MEMLO, and beyond that it will conflict with the loading address of the DUP menu. If you don't use DUP, I guess you have more flexibility. :)

 

EDIT: I just booted a DOS 2.5 disk, and can confirm that ?PEEK(1802) returns 131, for D1,D2,D8



#7 Mathy OFFLINE  

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Posted Tue Jan 29, 2019 5:25 PM

Hello guys

 

Try RAMdrive by Rafael James Espino.  (I've tried to find it just now, but didn't succeed.  I've used it in the past)

 

Sincerely

 

Mathy



#8 E474 ONLINE  

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Posted Tue Jan 29, 2019 5:28 PM

Hi,

 

  Thanks very much for the info.

 

  I wanted to use DOS 2.5 as it will run on pretty much any 8-bit, but it sounds like I can't have a very large Ramdisk, and also large files (> 200K) won't be supported.

 

  I'm guessing for this, MyDos would be a better bet? Can anyone recommend a best/latest version I should try (ideally an ATR set with sources, utilities, etc)?



#9 Nezgar OFFLINE  

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Posted Tue Jan 29, 2019 5:54 PM

Is there a particular oversion to SpartaDOS? 4.4x? It's ramdisk.sys natively supports up to 1MB of PORTB RAM.

(EDIT: Yes I missed you said "it will run on pretty much any 8-bit") :)

As for disk based DOSes, RealDos has one that does 1MB too, and there's HYPRAM by John Picken that does 1MB on Sparta 3.2 type dosses. (and is ridiculously fast) Maybe it also works on MyDOS? I haven't tried. (Although it might need to be manually formatted to MyDOS after)

"HyperSpeed Ramdisk v1.0"
http://www.mixinc.ne...ad_a8/sdcom.htm



#10 Mathy OFFLINE  

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Posted Wed Jan 30, 2019 2:42 AM

Hello E474

 

MyDOS 4.55 is the latest version.  You can find it at my MyDOS page.  MyDOS will support RAMdisks up to 1MB.

 

Sincerely

 

Mathy



#11 Larry OFFLINE  

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Posted Wed Jan 30, 2019 8:27 AM

If you are comfortable wth Dos 2.5, I think you'll find MyDos 4.5x very useful. If you get a hard drive at some point, Mydos supports up to 16 MB drives. I've used it for 30+ years.

#12 sanny OFFLINE  

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Posted Wed Jan 30, 2019 8:04 PM

MyDOS 4.55 is the latest version.  You can find it at my MyDOS page.  MyDOS will support RAMdisks up to 1MB.

 

Make the "<-- Currently latest version!" string better bold. Took some time for me to find it.

 

regards,
chris



#13 Mathy OFFLINE  

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Posted Thu Jan 31, 2019 1:51 PM

Hello Chris

 

I put them in chronological order a while ago.  That should be enough I think.

 

Sincerely

 

Mathy



#14 flashjazzcat ONLINE  

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Posted Thu Jan 31, 2019 1:53 PM

Reverse chronological (most recent at the top) might be more intuitive?



#15 E474 ONLINE  

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Posted Mon Feb 4, 2019 5:36 PM

Hi,

 

   I managed to get a 512K ramdisk working with MyDos and a Sys-Check card, and have uploaded an ATR to a new thread, at: http://atariage.com/...eck-2-512k-ram/

 

   Thanks for the help!







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