Article-I.D.: imsvax.479
Posted: Mon Dec 16 22:08:03 1985
Date-Received: Thu, 19-Dec-85 04:24:51 EST
Organization: IMS Inc, Rockville MD
Lines: 86
I've been working on expanding my 800XL to 256K as per the BYTE article.
I initially encountered trouble with the implementation and presumed that
the problem was in software (ATARIRAM.ASM from BYTEnet). Much to my dismay
and eventual glee, I discovered that the shielding of the XL had grounded
the circuit causing partial operation. With this corrected the 256K XL
expansion became operable. Therefore, the 9/85 BYTE article "The Quarter-
Meg Atari", with supporting software, by Claus Buchholz does indeed work
as published.
I wish to take this oppurtunity to thank all those individuals,
contributing to this net, for providing the insight and encouragement
necessary to have allowed me to continue this endeavor.
The BYTE implementation swaps 8 32K banks by manipulating PORTB bits
4, 5, and 6. The software provided will format a single virtual disk device
D3: or D4: as a single or double density device depending on the options
selected while assembling. The software will format the device to a full
720 sectors. Copying whole disks to the Ramdisk device is incredibly fast
during the Ramdisk access phases. (I've configured a special version that
uses two single density virtual devices. Copying between them is breath-
taking.)
Disadvantages: First, the 8 32K segments are not 130XE compatible.
Second, any interrupt encountered by a user program while the primary
bank (0-$7FFF) is swapped out will cause a crash.
Short of being a great Ram-Disk application, the BYTE implementation
leaves a lot to be desired. However, it is by no means a "dog" as it has
been referred. If all you want is RamDisk, some inexpensive electronics
project to play around with, and desire a do-able challenge; I fully
recommend the Project as described in BYTE. (by the way, I wield a
soldering-iron as a lumberjack would a scalpel).
There are alternatives, however. Some information I received from a
friend,having access to CompuServe, I am passing along in another posting.
The first, by John P. Radigan, describes RamDisk controllers (ERAMDSK1
and ERAMDSK2) for the 9/85 BYTE circuit. These controllers work with DOS
2.0, DOS 2.5, DOS XL, and SmartDOS (I typically use SmartDOS). The
controllers are "object" modules that can be obtained thru CompuServe.
(Didn't I see something about BINHEX on this net, recently?)
The second is a 130XE compatible upgrade to the original circuit by
Claus Buchholz himself. This article modifies the original circuit to
provide complete compatibility. The controller associated with it is
QMEGXLD.SRC. (I do not have a copy of this code. If anyone could obtain
it, particular Michigan netters in 517, I would appreciate a posting
either to this net or net.sources.)
Third, the Madison Area Atari Users Group (MAAUG) has a third version
called RAMBO-XL (256K) as well as Terminator-XL (512K). These work and have
been demonstrated according to their Newsletter. MAAUG offers pre-printed
circuited boards (un-drilled) for a token sum. (I've ordered 5 boards for
my User's Group and am awaiting delivery). Anyone interested should write
(preferrably thru a User's Group) to:
MAAUG
P.O. Box 56191
Madison, WI 53705
Ask for a copy of the Oct. and Nov. Newsletters ($5.00 should get some
circuit boards, I cannot speak for their production costs.)
Fourth, fellow netter C. David Young has been kind enough to pass along
the information on his 256KXL. He offers a hardware kit (board assembled)
for $99.95. I've seen this in a local store. It looks good, easy to
install, but the one I saw did not include software. This kit seems very
complete, however, you still have to be somewhat adventuresome to summon
up the courage to dismantle your XL. No sweat! The kit can be purchased
from:
CDY Consulting
421 Hanbee
Richardson, TX 75080
(214) 235-2146
Other products include: OMNIVIEW, OMNIMON, RAMROD, etc.
The Buchholz 2nd upgrade, the MAAUG upgrade, and the CDY upgrade all use
the same address scheme to switch 12 16k banks in $4000 - $7FFF using
bits 2,3,5,6 of PORTB. None are truly 100% compatible with the 130XE,
yet they are not really incompatible either. They merely extend bank
switching capability beyond that defined by Atari. All implementations are
compatible with each other, with the exception of the original BYTE
implementation.
-- Bob Burch