This model is almost same with 5551-R.
CPU is degraded to i486SX-33. The most distinctive feature of 5521 is that a
Cirrus GD5428 1MB SVGA /A was given for YSB
and YWB models instead of PS/55 Japanese Display Adapter.
- i486SX-33MHz CPU
- 3 mode 3.5" FDD ( 1.44MB/1.2MB/720KB )
- DBCS DA /NI-J for Y1B and Cirrus SVGA for YSB and YWB
- Support Streaming Data Transfer
Modified R/L planar
is used for this model (QFP IBM486DL2-66 is omitted from U1). 486SX33 sits on a
Socket 1 at U2. This planar has a jumper block at the location of
J6 on R /L planar. According to quick reference
the jumper should be turned on when a double-clock processor option is used
instead of a stock 486SX33 CPU.
Double-clock processor option (P/N 66G0727) is commonly used for 5551-L,
5551-Y and 5530-L.
There are no such jumpers on these system board (At least both 51-L and 30-L
has soldered QFP 486 CPUs.
Cirrus GD5428 SVGA /A (adapter ID: 917A)
Cirrus GD5428 SVGA /A (1MB VRAM standard but upgradeable to 2MB) was not
available as an "optional part". It's different from Cirrus SVGA used in Server
500 and is free from "flicker disease". There are solder pads for additional
VRAM and the circuit is ready for adding SOJ VRAM's. Win95 built-in driver can
use full 2MB but NT4 detects only 1MB.
Go HERE for more information about
the Cirrus SVGA adapter.